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1
Gaines-Das, R. E., A. F. Bristow, and H. Brettschneider. "The effects of common matrices for assay standards on performance of ‘ultra sensitive’ immunometric assays for TSH: Report of a joint WHO/IFCC collaborative study." Journal of Automatic Chemistry 13, no. 5 (1991): 209–15. http://dx.doi.org/10.1155/s1463924691000354.
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This report describes the results of a collaborative study organized by a joint working group of the IFCC and WHO and involving nine manufacturers of TSH immunometric assay kits. The study was designed to determine whether a calibrator with a common matrix gives better between-laboratory agreement for calibration of serum samples than the various kit calibrators, and to assess various materials for their suitability for use as common matrices. Kit calibrators, or calibrators consisting of the IRP for TSH made up in two common matrices: (a) serum from patients with untreated thyrotoxicosis or (b) serum taken from subjects treated with suppressive doses of triiodothyronine, gave similar results for the between-laboratory variation of estimates of TSH concentration for a range of serum samples. Dose-response curves for the two calibrators in ‘common’ matrices were similar to one another and to those for the kit calibrator. However, the occurrence of non-specific serum effects is shown by the comparison of results for these calibrators with results for calibrators made up in a third common matrix: serum treated with wheat germ lectin. Dose response curves for this calibrator were dissimilar to those for the other calibrators and between-laboratory variation for estimates in terms of this latter calibrator showed a substantial increase. Moreover, although the between-laboratory variances for estimates of the TSH concentration in terms of each of these calibrators (except those made up in serum treated with the wheat germ lectin) were similar for any one sample from five hyperthyroid patients, the variances were not consistent between samples, even for samples with similar mean TSH concentrations. These results suggest that a major factor in the between-laboratory variation, especially in the region near ‘zero dose’, is sample-related, and is caused by particular samples interacting differently with different assay systems.In general, it would appear that for the well-controlled ‘ultrasensitive’ TSH immunometric assay kits, included in this study, between-laboratory agreement of estimates of the TSH concentration in serum samples is not likely to be substantially improved by use of a common matrix for the standards.
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Caliendo, Angela M., Mona D. Shahbazian, Carl Schaper, Jessica Ingersoll, Deborah Abdul-Ali, Jerry Boonyaratanakornkit, Xiao-Li Pang, Julie Fox, Jutta Preiksaitis, and E. Ralf Schönbrunner. "A Commutable Cytomegalovirus Calibrator Is Required to Improve the Agreement of Viral Load Values between Laboratories." Clinical Chemistry 55, no. 9 (September 1, 2009): 1701–10. http://dx.doi.org/10.1373/clinchem.2009.124743.
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Abstract Background: Viral load testing for cytomegalovirus (CMV) is an important diagnostic tool for the management of transplant recipients and immunocompromised individuals; however, inconsistency among laboratories in quantitative measurements of viral load limits interinstitutional comparisons. These inconsistencies stem from the lack of assays cleared by the US Food and Drug Administration, the absence of international standards, the wide variety of CMV-extraction and -detection methods, and differences in materials used for calibration. A critical component of standardization is the use of calibrators that are traceable and commutable. Methods: Bland–Altman plots and prediction ellipses were used to test the commutability of 2 CMV calibrators for 2 different quantification methods. Results: Tests with 2 methods showed 1 calibrator to be commutable and the other to be noncommutable. The results for the commutable calibrator were within the 95% prediction interval of the clinical samples in the Bland–Altman plot and within the 95% prediction ellipse for a simulated commutable calibrator, whereas the results for the noncommutable calibrator were not within these prediction intervals. When used to calibrate patient results, only the commutable calibrator, the OptiQuant® CMVtc Calibration Panel, significantly improved the comparability of viral loads for the 2 different measurement methods. Conclusions: This study demonstrates that an important goal in the effort to improve healthcare for patients with CMV-related disease is the establishment of traceable and commutable reference materials, including both calibrators and controls. .
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Hill, R. P. "The Effect of Calibration on the between-Laboratory Variation of Serum Fructosamine." Annals of Clinical Biochemistry: International Journal of Laboratory Medicine 25, no. 4 (July 1988): 435–39. http://dx.doi.org/10.1177/000456328802500422.
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Human pooled serum from diabetic and non-diabetic subjects, and calibrators containing glycated protein or 1-deoxy-1-morpholinofructose (DMF) in a variety of matrices, were distributed to 10 laboratories. When they used their own assay conditions and calibrators, the inter-laboratory variation was unacceptably high. However, when the pool from diabetic patients was reassayed using a calibrator with an assigned value prepared from freeze-dried human serum, and containing no DMF, inter-laboratory variation was reduced significantly. Interlaboratory agreement for the pool from non-diabetic subjects remained poor despite recalibration. Recalibration using either serum or albumin based solutions of DMF as calibrator failed to effect any significant reductions in inter-laboratory variation. Secondary calibrators based on a protein matrix with no added DMF are recommended for routine use.
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Baadenhuijsen, Henk, Ruud Scholten, Hans L. Willems, Cas W. Weykamp, and Rob T. P. Jansen. "A model for harmonization of routine clinical chemistry results between clinical laboratories." Annals of Clinical Biochemistry: International Journal of Laboratory Medicine 37, no. 3 (May 1, 2000): 330–37. http://dx.doi.org/10.1258/0004563001899230.
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Clinical chemistry laboratory results from different laboratories often show large between-laboratory variation due to factors such as differences in method principles, method applications, calibration procedures or the application of different instrument factor settings within the same calibration procedure. We have examined the possible use of common calibrators to reduce this variation. Three different calibrators were compared: A, freeze-dried preparations of pooled patients' serum samples, spiked to give three concentration levels; B, freeze-dried preparations of pooled patients' serum samples selected on the basis of elevated enzyme activities at three levels; C, a single calibrator consisting of frozen pooled serum samples. These calibrators were sent to 11 participating laboratories together with 14 fresh patients' serum samples. We report the variation of the results of 21 general clinical chemistry analytes obtained in the patients' serum samples before and after recalculation on the basis of the results of the calibrators. For most analytes the use of a multiple point linear regression calibration function is able to reduce the between-laboratory variation considerably from more than 30% (enzymes) to values well within the bias limits set by European quality specifications, when the necessary conditions are met. These conditions include the commutability of the calibrator(s) with fresh patients' material. For the enzymes, calibrator material originating from selectively pooled patients' samples appeared to be necessary, whereas for the substrates selectively pooled serum calibrators spiked with exogenous supplements may be used. For harmonization to be effective in practice, calibrators need to be stable over time and to carry assigned values set by certified reference laboratories, and the quality performance of participating laboratories should be appropriately monitored.
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Lessinger, J. M., J. L. Dourson, and G. Férard. "Importance of standardization of lipase assays by using appropriate calibrators." Clinical Chemistry 42, no. 12 (December 1, 1996): 1979–83. http://dx.doi.org/10.1093/clinchem/42.12.1979.
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Abstract Comparability of lipase catalytic activities was poor when lipase was determined in 50 patients' specimens by a turbidimetric (Boehringer) and a colorimetric (Sigma) assay. Mean values of results differed by a ratio of 2.39. Optimal common conditions were defined for the titration of lipase activity in two commercial calibrators and in a home-purified preparation of human pancreatic lipase (HPL). When using these titers for each calibrator, comparability was greatly improved (ratio = 1.25). This result indicates that a significant part of between-method discrepancy is due to the lack of a reference method for the titration of lipase calibrators. Intermethod behavior of each material was compared with that of patients' specimens. By using HPL as calibrator, comparability was still dramatically improved (ratio = 1.01). This study shows the importance of the validation of a material for defined routine measurement procedures, before its use as calibrator.
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Duan, Lei, and Yang Zhang. "Optimization Design in Cooling Channels of Calibrator for Plastic Profile Extrusion Based on Numerical Simulation." Applied Mechanics and Materials 494-495 (February 2014): 677–80. http://dx.doi.org/10.4028/www.scientific.net/amm.494-495.677.
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Hot plastic profile produced by extrusion die is cooled down and calibrated by calibrator. Therefore, the cooling and calibrating ability of the calibrator directly influence the quality and output of the profile. The key is to design the distribution of cooling channels in calibrator. By analyzing the heat transfer process during cooling in calibrator, the cooling process of plastic profile in calibrator is simulated. Based on the finite element analysis results, the optimization objective is established to obtain the cooling efficiency and uniformity of each node in the profile cross sections of the calibrators exit and finish the optimization design of the cooling channels positions.
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Adcock, Dorothy, Emily M. Hawes, Suzanne J. Francart, Russell P. Grant, Stephan Moll, and Robert C. Gosselin. "Evaluating the use of commercial drug-specific calibrators for determining PT and APTT reagent sensitivity to dabigatran and rivaroxaban." Thrombosis and Haemostasis 113, no. 01 (January 2015): 77–84. http://dx.doi.org/10.1160/th14-04-0361.
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SummarySuitable laboratory methodologies for quantifying the non-vitamin K oral anticoagulants (NOAC) include liquid chromatography-tandem mass spectrometry (LC-MS/MS) or drug-calibrated assays such as the dilute thrombin time for dabigatran or anti-Xa measurements for rivaroxaban. In situations when these tests are unavailable, it has been suggested that using commercial drug calibrators on APTT and PT assays would theoretically provide reagent sensitivity to these drugs. The purpose of this study was to determine whether commercial drug calibrators deliver similar reagent sensitivity information as samples from patients receiving dabigatran or rivaroxaban as part of their routine care. Two laboratory sites tested commercial calibrator material for dabigatran and rivaroxaban (Hyphen Biomedical) using PT and APTT reagents and data was compared to samples collected from patients taking NOACs that were quantified by LC-MS/MS. Correlation statistics and calculating the amount of drug required to double the clotting time of normal plasma were performed. All drug calibrator material correlated more strongly (R2> 0.95) for any reagent/drug combination than patient samples (R2 ranged from 0.29–0.86). Dabigatran calibrator results and patient data were equivalent for SynthASil and PTT-A APTT reagents. The dabigatran and rivaroxaban calibrator material over-estimated drug sensitivity for all PT reagents when compared to sensitivity data calculated based on drug levels obtained by LC-MS/MS from patient samples. In conclusion, drug-specific calibrators overestimated reagent sensitivity which may underestimate in vivo drug concentration in a given patient. Further studies are required to assess whether this method of determining relative sensitivity of NOAC on routine coagulation assays should be recommended.
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Hackett, John, Jane Hoff-Velk, Alan Golden, Jeff Brashear, John Robinson, Margaret Rapp, Michael Klass, David H. Ostrow, and Wlodek Mandecki. "Recombinant Mouse-Human Chimeric Antibodies as Calibrators in Immunoassays That Measure Antibodies toToxoplasma gondii." Journal of Clinical Microbiology 36, no. 5 (1998): 1277–84. http://dx.doi.org/10.1128/jcm.36.5.1277-1284.1998.
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In the present study, we examined the feasibility of using recombinant antibodies containing murine variable regions and human constant regions as calibrators or controls in immunoassays. As a model system, we chose the Abbott IMx Toxo immunoglobulin M (IgM) and Toxo IgG assays designed to detect antibodies to Toxoplasma gondii. Two mouse monoclonal antibodies were selected based on their reactivity to the T. gondii antigens P30 and P66. Heavy- and light-chain variable-region genes were cloned from both hybridomas and transferred into immunoglobulin expression vectors containing human kappa and IgG1 or IgM constant regions. The constructs were stably transfected into Sp2/0-Ag14 cells. In the IMx Toxo IgG assay, immunoreactivity of the anti-P30 chimeric IgG1 antibody paralleled that of the positive human plasma-derived assay calibrators. Signal generated with the anti-P66 chimeric IgG1 antibody was observed to plateau below the maximal reactivity observed for the assay calibrator. Examination of the IgM chimeric antibodies in the IMx Toxo IgM assay revealed that both the anti-P30 and anti-P66 antibodies matched the assay index calibrator manufactured with human Toxo IgM-positive plasma. When evaluated with patient samples, the correlation between results obtained with the chimeric antibody calibrators and the positive human plasma calibrators was ≥0.985. These data demonstrate that chimeric mouse-human antibodies are a viable alternative to high-titer positive human plasma for the manufacture of calibrators and controls for diagnostic assays.
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Chen, Z., A. Prestigiacomo, and T. A. Stamey. "Purification and characterization of prostate-specific antigen (PSA) complexed to alpha 1-antichymotrypsin: potential reference material for international standardization of PSA immunoassays." Clinical Chemistry 41, no. 9 (September 1, 1995): 1273–82. http://dx.doi.org/10.1093/clinchem/41.9.1273.
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Abstract We describe for the first time a protocol to purify to apparent homogeneity an in vitro-prepared complex of prostate-specific antigen (PSA) and alpha 1-antichymotrypsin (ACT) by using a combination of gel filtration and ion-exchange chromatography. The purity of the PSA-ACT complex was confirmed by gel electrophoresis and Western blot. The PSA-ACT complex was stable in the pH range 6.0 to 7.8; it was also stable in various matrices, temperatures, and high concentrations of salt. Purification of the PSA-ACT complex was highly reproducible. An absorptivity of 0.99 L x g-1 x cm-1 at 280 nm was assigned to the PSA-ACT complex, based on amino acid analysis. Because PSA and ACT bind in a 1:1 molar ratio, we determined the molecular mass of the PSA-ACT complex as the mass encoded by the cDNA of ACT (plus 26% carbohydrate) plus the molecular mass of PSA (28,430 Da), which totals 89,280 Da. Using this material, we made two common calibrators, one of 100% PSA-ACT complex and one of 90% PSA-ACT complex plus 10% free PSA by volume (90:10 calibrator). Substitution of these calibrators for the manufacturers' calibrators in nine commercial immunoassays substantially reduced differences between immunoassays, especially for serum PSA values between 4 and 10 micrograms/L. The 90:10 calibrator is recommended as a universal calibrator for international standardization of PSA immunoassays.
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Korecka, Magdalena, Michal J. Figurski, Susan M. Landau, Magdalena Brylska, Jacob Alexander, Kaj Blennow, Henrik Zetterberg, William J. Jagust, John Q. Trojanowski, and Leslie M. Shaw. "Analytical and Clinical Performance of Amyloid-Beta Peptides Measurements in CSF of ADNIGO/2 Participants by an LC–MS/MS Reference Method." Clinical Chemistry 66, no. 4 (January 31, 2020): 587–97. http://dx.doi.org/10.1093/clinchem/hvaa012.
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Abstract Background Cerebrospinal fluid (CSF) amyloid-β1-42 (Aβ42) reliably detects brain amyloidosis based on its high concordance with plaque burden at autopsy and with amyloid positron emission tomography (PET) ligand retention observed in several studies. Low CSF Aβ42 concentrations in normal aging and dementia are associated with the presence of fibrillary Aβ across brain regions detected by amyloid PET imaging. Methods An LC–MS/MS reference method for Aβ42, modified by adding Aβ40 and Aβ38 peptides to calibrators, was used to analyze 1445 CSF samples from ADNIGO/2 participants. Seventy runs were completed using 2 different lots of calibrators. For preparation of Aβ42 calibrators and controls spiking solution, reference Aβ42 standard with certified concentration was obtained from EC-JRC-IRMM (Belgium). Aβ40 and Aβ38 standards were purchased from rPeptide. Aβ42 calibrators’ accuracy was established using CSF-based Aβ42 Certified Reference Materials (CRM). Results CRM-adjusted Aβ42 calibrator concentrations were calculated using the regression equation Y (CRM-adjusted) = 0.89X (calibrators) + 32.6. Control samples and CSF pools yielded imprecision ranging from 6.5 to 10.2% (Aβ42) and 2.2 to 7.0% (Aβ40). None of the CSF pools showed statistically significant differences in Aβ42 concentrations across 2 different calibrator lots. Comparison of Aβ42 with Aβ42/Aβ40 showed that the ratio improved concordance with concurrent [18F]-florbetapir PET as a measure of fibrillar Aβ (n = 766) from 81 to 88%. Conclusions Long-term performance assessment substantiates our modified LC–MS/MS reference method for 3 Aβ peptides. The improved diagnostic performance of the CSF ratio Aβ42/Aβ40 suggests that Aβ42 and Aβ40 should be measured together and supports the need for an Aβ40 CRM.
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Krbal, Michal, Ludek Pelikan, Jaroslav Stepanek, Jaroslava Orsagova, and Iraida Kolcunova. "A Physical Calibrator for Partial Discharge Meters." Energies 12, no. 11 (May 29, 2019): 2057. http://dx.doi.org/10.3390/en12112057.
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This article offers an alternative method of calibrating partial discharge meters for research and teaching purposes. Most current modern calibrators are implemented as precise voltage pulse sources with a coupling capacitor. However, our calibrator is based on the physical principles of dielectric materials distributed in a plane or space. Calibrator design is unique and there is an attempt to get closer to the behavior of the measured real objects. The calibration impulses are created by energy from a high voltage power supply at the specific or nominal value of the applied voltage. At the same time, it is possible to simulate the value and quantity of the discharges and their position in the object relative to the input electrodes. The calibrator creates conditions as a real measured object with adjustable parameters. This paper describes a design of this type of calibrator, its implementation, numerical simulation of discharge values and laboratory measurements with functional verification using the Tettex 9520 calibrator and galvanic measured system DDX 7000/8003 and DDX 9121b. All measurements are carried out using the CVVOZEPowerLab Research Infrastructure equipment.
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Blanc, J. A., V. A. Manneh, R. Ernst, D. E. Berger, S. A. de Keczer, C. Chase, J. M. Centofanti, and A. J. DeLizza. "Adsorption losses from urine-based cannabinoid calibrators during routine use." Clinical Chemistry 39, no. 8 (August 1, 1993): 1705–12. http://dx.doi.org/10.1093/clinchem/39.8.1705.
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Abstract The major metabolite of cannabis found in urine, 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid (delta 9-THC), is the compound most often used to calibrate cannabinoid immunoassays. The hydrophobic delta 9-THC molecule is known to adsorb to solid surfaces. This loss of analyte from calibrator solutions can lead to inaccuracy in the analytical system. Because the calibrators remain stable when not used, analyte loss is most probably caused by handling techniques. In an effort to develop an effective means of overcoming adsorption losses, we quantified cannabinoid loss from calibrators during the testing process. In studying handling of these solutions, we found noticeable, significant losses attributable to both the kind of pipette used for transfer and the contact surface-to-volume ratio of calibrator solution in the analyzer cup. Losses were quantified by immunoassay and by radioactive tracer. We suggest handling techniques that can minimize adsorption of delta 9-THC to surfaces. Using the appropriate pipette and maintaining a minimum surface-to-volume ratio in the analyzer cup effectively reduces analyte loss.
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Hainline, A., J. M. Karon, C. L. Winn, and J. B. Gill. "Accuracy and comparability of long-term measurements of cholesterol." Clinical Chemistry 32, no. 4 (April 1, 1986): 611–15. http://dx.doi.org/10.1093/clinchem/32.4.611.
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Abstract Laboratories of the Lipid Research Clinics Program (LRC) maintained the accuracy of their measurements of total cholesterol by using seven pooled serum calibrators supplied by the Centers for Disease Control (CDC). Over the 11-year life of the LRC, each calibrator was prepared in succession and a target value was assigned by the CDC reference method for cholesterol. The results of a special experiment in which six of the seven calibrators were analyzed simultaneously demonstrated that the target values were accurately assigned. Deviations of the target values from the experimental means ranged from zero to 1.7% of the original target value. The experiment revealed no evidence of drift in the bias of the reference method over the life of LRC and demonstrated the accuracy, consistency, and the comparability of the values assigned to the successive calibrator pools used by the LRC laboratories during more than eight years. It demonstrated the reliability of a reference method and the suitability of frozen serum pools for maintaining an accurate measurement base for serum cholesterol.
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Schlain, Brian. "A stochastic approximation method for assigning values to calibrators." Clinical Chemistry 44, no. 4 (April 1, 1998): 839–48. http://dx.doi.org/10.1093/clinchem/44.4.839.
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Abstract A new procedure is provided for transferring analyte concentration values from a reference material to production calibrators. This method is robust to calibration curve-fitting errors and can be accomplished using only one instrument and one set of reagents. An easily implemented stochastic approximation algorithm iteratively finds the appropriate analyte level of a standard prepared from a reference material that will yield the same average signal response as the new production calibrator. Alternatively, a production bulk calibrator material can be iteratively adjusted to give the same average signal response as some prespecified, fixed reference standard. In either case, the outputted value assignment of the production calibrator is the analyte concentration of the reference standard in the final iteration of the algorithm. Sample sizes are statistically determined as functions of known within-run signal response precisions and user-specified accuracy tolerances.
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Gosselin, Robert C., Dorothy M. (Adcock) Funk, J. Michael Taylor, Suzanne J. Francart, Emily M. Hawes, Kenneth D. Friedman, and Stephan Moll. "Comparison of Anti-Xa and Dilute Russell Viper Venom Time Assays in Quantifying Drug Levels in Patients on Therapeutic Doses of Rivaroxaban." Archives of Pathology & Laboratory Medicine 138, no. 12 (December 1, 2014): 1680–84. http://dx.doi.org/10.5858/arpa.2013-0750-oa.
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Context Rivaroxaban is a new oral anticoagulant that functions as a direct anti-Xa inhibitor. Although routine monitoring is not required, measurement of plasma concentrations may be necessary in certain clinical situations. Routine coagulation assays, such as the prothrombin time and, to a lesser degree, activated partial thromboplastin time, correlate with drug concentration, but because of reagent variability, these methods are not reliable for determining rivaroxaban anticoagulation. Objective To compare different methods and calibrators for measuring rivaroxaban, including the chromogenic anti-Xa assay, which, when calibrated with a rivaroxaban standard, may be more appropriate for determining anticoagulation. Design We compared measured rivaroxaban concentrations with the same anti-Xa kit but used different calibrators, with different anti-Xa kits but the same calibrators, with antithrombin-supplemented anti-Xa kit versus nonsupplemented kits, and with 2 methods based on rivaroxaban-calibrated, high-phospholipid, dilute Russell viper venom time. Regression and paired t test statistics were used to determine correlation and significant differences among methods and calibrator sources. Results Although there was strong correlation, statistically significant biases existed among methods that report rivaroxaban levels. A single-source calibrator did not alleviate those differences among methods. High-phospholipid Russell viper venom reagents correlated with rivaroxaban concentration but were not better than chromogenic anti-Xa methods. Conclusions Rivaroxaban-calibrated, anti-Xa measurements correlate well, but the clinical significance of the variation with rivaroxaban measurements is uncertain. The antithrombin-supplemented, anti-Xa method should be avoided for measuring rivaroxaban.
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Haese, Alexander, Ville Vaisanen, Judith A. Finlay, Kim Pettersson, Harry G. Rittenhouse, Alan W. Partin, Debra J. Bruzek, Lori J. Sokoll, Hans Lilja, and Daniel W. Chan. "Standardization of Two Immunoassays for Human Glandular Kallikrein 2." Clinical Chemistry 49, no. 4 (April 1, 2003): 601–10. http://dx.doi.org/10.1373/49.4.601.
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Abstract Background: Measurement of human kallikrein 2 (hK2) has improved early detection and staging of prostate cancer. However, reported concentrations of hK2 among currently used assays have not been standardized in any way. We compared two hK2 assays and five different recombinant hK2 variants (rhK2) and suggest a common calibrator as an important step and putative reference substance in hK2 assay standardization. Methods: We measured 146 sera by two hK2 assays, using assay-specific calibrators to assess the difference between the two assays. Serial dilutions of five rhK2 preparations were measured repeatedly, with one preparation assigned as calibrator and the others as unknowns to define which variant provided the closest match between the two assays. This rhK2 variant was used to recalibrate both assays. We measured hK2 concentrations in the same 146 patients to evaluate the change in the difference. Results: Use of assay-specific calibrators for comparison of the two assays yielded a Deming regression equation of: y = 0.789 (95% confidence interval, 0.674–0.922)x + 0.014 (0.004–0.025) μg/L; R2 = 0.667. Analysis of five rhK2 variants revealed that the enterokinase (ek)-rhK2 form provided the best match between both assays. Using the ek-rhK2 as a common calibrator, we observed a change in the slope of the regression curve to: y = 1.106 (0.872–1.340)x + 0.006 (−0.002 to 0.016) μg/L; R2 = 0.648, suggesting an increase in the mean estimate of agreement between the two assays. Conclusion: Calibration with a common calibrator substantially increased agreement between the assays. The ek-rhK2 variant provided the best performance of all tested rhK2 variants and should undergo mass spectrometry and amino acid analysis for exact mass determination and value assignment to evaluate its potential as a reference material for immunoassays for hK2.
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Lai, K. Kay-Yin, Linda Cook, Elizabeth M. Krantz, Lawrence Corey, and Keith R. Jerome. "Calibration Curves for Real-Time PCR." Clinical Chemistry 51, no. 7 (July 1, 2005): 1132–36. http://dx.doi.org/10.1373/clinchem.2004.039909.
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Abstract Background: Despite the increasing use of real-time PCR in the diagnosis and management of viral infections, there are no published studies adequately addressing the optimum number of calibrators, the number of replicates of each calibrator, and the frequency with which calibration needs to be repeated. This study was designed to address these issues. Methods: Cycle threshold data (ABI 7700) was collected from >50 consecutive real-time PCR runs for hepatitis B and Epstein–Barr viruses. Our routine calibration curve made from serial 10-fold dilutions run in duplicate was compared with alternative options, including duplicate 100-fold dilutions, inclusion of a low-copy calibrator, and omission of the duplicate determination. Control data were used to examine the use of an average calibration curve made from multiple runs. Results: Use of duplicate serial 10-fold dilutions led to the least imprecision, duplicate 100-fold dilutions had slightly higher imprecision, and calibration curves obtained with singlet measurements showed the greatest imprecision. For patient data, the duplicate 100-fold dilution calibration curve produced results that best matched those from the routine calibration curve. Use of singlet dilutions or inclusion of a low-copy calibrator produced poorer agreement. Variability in controls was lower with a daily calibration curve than with an average calibration curve. Conclusions: Duplicate 100-fold dilution calibration curves produced equivalent results and the same imprecision as curves with more calibrators, and thus are a valid alternative. Laboratories should carefully evaluate the variability resulting from the use of average calibration curves before adopting this approach.
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Savelkaev, Sergei V. "UNIVERSAL COAXIAL-STRIPLINE AND PROBE TEST FIXTURES AND THEIR CALIBRATION METHODS." Vestnik SSUGT (Siberian State University of Geosystems and Technologies) 25, no. 4 (2020): 229–37. http://dx.doi.org/10.33764/2411-1759-2020-25-4-229-237.
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The design and calibration method for a coaxial-stripline test fixture that provides connection of microwave circuit analyzer of both coaxial measures and microstrip calibrators, as well as the active components under study, such as transistors, are considered. The test fixture provides high repeatability of connecting coaxial measures, microstrip calibrators, and active components being studied and has a small standing-wave ratio and loss. The test fixture is calibrated with using a minimal set of easily calculated microstrip calibrators with low losses, which, taking into account the high repeatability of their connection, reduces the complexity of its calibration and increases the accuracy of transmitting measurement results from the coaxial line to the microstrip line. The possibility of transmitting measurement results from the coaxial line to the microstrip line extends the scope of the State System for Ensuring the Uniformity of Measurements to the microstrip line. The design of the probe test fixture and a method of its calibration by a specialized microstrip calibrator are also given.
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Tincani, Angela, Marielle Sanmarco, Philippe de Moerloose, Marie-Claire Boffa, and Guido Reber. "Variability of anti-β2 glycoprotein I antibodies measurement by commercial assays." Thrombosis and Haemostasis 94, no. 09 (2005): 665–72. http://dx.doi.org/10.1160/th05-02-0081.
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SummaryThe aim of this study was to evaluate the agreement in assay results between commercial kits for the measurement of anti- β2glycoprotein I antibodies. Ten manufacturers provided one IgG and one IgM kit to three testing centres. Samples from patients with primary (n=13) or secondary (n=3) antiphospholipid syndrome (APS), from lupus patients without APS features (n=6) and from normal individuals (n=2) were tested in the three centres according to manufacturers’ instructions. Dilutions in normal serum of a pool made from positive patients’ samples (Forum Calibrators) and dilutions of humanized monoclonal antibodies (MoAbs) were used as additional calibrators. The calibration curves obtained with each calibrator differed widely between kits. The rate of positivity of patients’ samples varied from 7 to 16 for IgG and from 2 to 17 for IgM, depending on the kit. Perfect agreement occurred in 12/22 samples for IgG and 5/22 samples for IgM. Samples from normals were found negative by all kits. Between kits, cutoff values varied up to five fold when expressed in Forum Calibrators arbitrary units and up to three fold when expressed in MoAbs equivalents. Examination of discrepant samples indicated that about half of the discrepancies, scoring 8:2 and 9:1, involved the same few kits. In highly discrepant samples, some kits appeared as high responders as compared to others. In conclusion, with the exception of a few kits, agreement in assay results was acceptable. In conclusion, additional efforts are however necessary, especially concerning the way to assess the cutoff point and the adoption of a reference calibrator, in order to improve standardization of the assays.
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Yatsuk, V., R. Matviiv, and Yu Yatsuk. "Metrological Properties Analysis of Portable Dc Voltage Calibrator with Errors Correction." Metrology and instruments, no. 4 (August 30, 2018): 33–40. http://dx.doi.org/10.33955/2307-2180(4)2018.33-40.
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It is shown that, it is expedient to use a DC voltage calibrator with automatic error correction by double switching inverting method and averaging the output voltage with a low frequency filter for operational monitoring and remote calibration of measuring channels was shown in this paper (Figre 1). A comparison of the dynamic and metrological characteristics of DC voltage calibrators with single- and two-period demodulation has been carried out and operator and time mathematical models have been proposed (Figure 2). Computer simulation of both structures of voltage calibrators in manual and automatic control modes was carried out. The results of experimental studies of a DC voltage calibrator model with single-phase demodulation and averaging by an active low frequency filter are described (Figure 3). Conclusions about the good convergence of experimental results with theoretical assumptions were made; the unadjusted value of the additive displacements in the manual control mode did not exceed ±1 μV. A certain frequency dependence of the additive displacements unadjusted value of the made model has been established and it is determined that its minimum value is at a frequency near 1.2 kHz. Conditions of practical realization of a DC voltage calibrator with automatic correction of additive displacements by the proposed method of switching inverting in the basis of programmable systems on a chip are discussed. Emphasized that in the future it will also adjust the multiplier and additional errors during the reproduction of DC voltage small values in working conditions.
The scientific results, presented in this article, were obtained in the frame of research project number 0115U000446, 01.01.2015 - 31.12.2017, financially supported by the Ministry of Education and Science of Ukraine.
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Nikolajevs, A., and K. Prūsis. "The LOFAR Long-Baseline Calibrator Survey Classification." Latvian Journal of Physics and Technical Sciences 57, no. 1-2 (April 1, 2020): 34–40. http://dx.doi.org/10.2478/lpts-2020-0005.
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AbstractData manipulation of the LOFAR Long-Baseline Calibrator Survey (LBCS) and the Westerbork Northern Sky Survey (WENSS) catalogues are carried out in the present study. The aim of the study is to make calibrator classification statistics plots and estimations for further observations and upcoming stations. First, mean flux densities of LBCS calibrators against declination and observed station baseline length to the tied core station are plotted and the classified sources are marked. Second, we provide the designation – naming it the success rate – for the number of sources with the correlated signal against all the LBCS catalogue sources. Third, there is a trend in mean peak flux densities between stations – longer the baseline, higher mean peak flux density. Finally, estimations for upcoming and recent stations are made and some results are not encouraging.
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Holland, W. P., W. Boender, J. A. Bos, and P. E. Huygen. "A simple handheld push-button device for in situ calibration of pneumotachographs." Journal of Applied Physiology 77, no. 4 (October 1, 1994): 2042–47. http://dx.doi.org/10.1152/jappl.1994.77.4.2042.
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A simple and compact flow calibrator has been devised for generating precise predetermined constant flow rates for checking the calibration of laboratory and clinical flow transducers used in respiratory measurements. The standard version delivers preset flows of 0.5 and 1 l/s, whereas a tuned-up version can produce preset flows of 2.5 and 5 l/s, with an accuracy of +/- 2%. The pressure generated is sufficient to cope with most commonly used respiratory flowmeters. The flow calibrator is built from inexpensive components that are readily obtainable: a fan, a turbine flowmeter, and a feedback circuit in a compact housing. The device is easy to connect to other equipment and to operate. Three flow calibrators have been built and are in regular use in a lung function laboratory and on intensive care wards.
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Afonso, J., B. Ricken, T. Schuster, D. Guschin, and M. Schneider. "P229 Standardization of Quantum Blue® rapid TDM assays with WHO international standards for adalimumab and infliximab." Journal of Crohn's and Colitis 15, Supplement_1 (May 1, 2021): S279—S280. http://dx.doi.org/10.1093/ecco-jcc/jjab076.355.
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Abstract Background Therapeutic drug monitoring of inflammatory bowel disease (IBD) patients under anti-TNF therapy is based on trough level determination of the drug. Rapid assays and multiple ELISAs are available that measure anti-TNF biologics. An international standard is required to improve comparability among different assays. Recently, WHO introduced anti-TNF standards for adalimumab (ADL) and infliximab (IFX). A WHO international reference material (IRM) based standardization is crucial for the harmonization of assays available on the market. Methods The aim of the study was to standardize the BÜHLMANN Quantum Blue® ADL and BÜHLMANN Quantum Blue® IFX based on the WHO IRM for ADL and IFX, respectively. A value transfer from the WHO reference material to the internal calibrator sets for both assays was based on a protocol previously described by Blirup-Jensen et al. (Clin Chem Lab Med 2001; 39(11):1110–1122) and by means of a commercially available ELISA. A method comparison of the ELISA and the rapid test was carried out before the value transfer to guarantee comparability of both assays. Additionally, the correlation of the WHO IRM with the currently used calibrator material was determined for ADL. The correlation of the WHO IFX standard (NIBSC 16/170) with the currently used calibrator material was presented recently (Keller et al. 2020, UEGW 2020). Calibration curves were generated with BÜHLMANN ADL calibrators and with calibrators made from WHO IRM for ADL (NIBSC 17/236). Serum samples, covering a concentration range from 1.0 to 35 µg/mL, were analysed with both calibration curves and compared by Bland-Altman and Passing-Bablok analysis. Results A preliminary value transfer study revealed an relative uncertainty of 12.3% for both drugs. A good comparison of the ADL and IFX rapid test and the ELISA is given: Passing-Bablok correlation coefficient (R) of 0.953 (ADL) and 0.942 (IFX), and a mean bias determined by Bland-Altman of 1.59 µg/mL (ADL) and -0.5 µg/mL (IFX), respectively. The sample values gained with BÜHLMANN calibrators showed an excellent correlation with values gained with the WHO international standard for ADL as calibrator. Passing-Bablok regression analysis revealed a slope of 1.3 and correlation coefficient (R) of 1.0. Conclusion To the best of our knowledge, the Quantum Blue® ADL and Quantum Blue® IFX, are the first commercially available quantitative lateral flow assays comprising a WHO based standardization. Additionally, it was demonstrated that the current standardizations of Quantum Blue® ADL correlates very well with the WHO international standard for ADL.
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Herbst, Zackary, Coleman T. Turgeon, Chad Biski, Hamid Khaledi, Nancy B. Shoemaker, Patrick D. DeArmond, Sara Smith, Joseph Orsini, Dietrich Matern, and Michael H. Gelb. "Achieving Congruence among Reference Laboratories for Absolute Abundance Measurement of Analytes for Rare Diseases: Psychosine for Diagnosis and Prognosis of Krabbe Disease." International Journal of Neonatal Screening 6, no. 2 (March 31, 2020): 29. http://dx.doi.org/10.3390/ijns6020029.
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Measurement of the absolute concentration of the biomarker psychosine in dried blood spots (DBS) is useful for diagnosis and prognosis of Krabbe disease and to support newborn screening of this leukodystrophy. As for assays for more common diseases, it is important to achieve congruence when multiple clinical laboratories provide testing. Four clinical laboratories, one research laboratory, and a commercial vendor collaborated with the goal to achieve congruence in quantitative psychosine measurement in DBS. A set of DBS calibrators was prepared by a single vendor and used in each reference laboratory to make a standard curve of measured psychosine in DBS versus the stated calibrator psychosine level. Congruence between the participating five laboratories was achieved using the psychosine DBS calibrators. This allowed application of disease-specific reference ranges obtained by the reference laboratory with the most extensive data by the other reference laboratories. Congruence between multiple reference laboratories in the measurement of the absolute concentration of biomarkers in DBS (and by extension other samples) is possible by the use of a common set of DBS calibrators.
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Caponi, Laura, Elona Koni, Nadia Romiti, Aldo Paolicchi, and Maria Franzini. "Different immunoreactivity of monomers and dimers makes automated free light chains assays not equivalent." Clinical Chemistry and Laboratory Medicine (CCLM) 57, no. 2 (December 19, 2018): 221–29. http://dx.doi.org/10.1515/cclm-2018-0412.
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Abstract Background The automated immunochemical serum free light chains (FLC) assays, Freelite (a polyclonal antiserum) and N Latex FLC (a mixture of monoclonal antibodies), are not interchangeable, as they may provide different results on a same sample. This study was aimed to establish if the calibrators contain FLC oligomers, and if different reactivity against monomers and dimers contributes to the discrepancy. Methods Gel filtration chromatography fractions of the calibrators were subjected to a Western blot (WB) and analyzed by each reagent. The procedure was repeated after pretreating the N Latex FLC calibrator with the reducing agent dithiothreitol (DTT). Results Both calibrators contain FLC dimers and monomers. Both reagents detect (with different sensitivity) FLC kappa monomers and dimers; instead, Freelite detects only FLC lambda dimers, while N Latex FLC detects only FLC monomers. After DTT treatment, only the N Latex lambda still detects FLC with reduced protein thiols, while the reactivity of all other reagents is abolished. Conclusions Due to their different reactivity against FLC monomers and oligomers, the Freelite and N Latex FLC are calibrated against different components of their own calibrators, making the two reagents not equivalent. The redox status of FLC determines the immunoreactivity not only of FLC dimers, but also of the monomers.
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Rioja, M., R. Dodson, G. Orosz, and H. Imai. "MultiView High Precision VLBI Astrometry at Low Frequencies." Proceedings of the International Astronomical Union 13, S336 (September 2017): 439–42. http://dx.doi.org/10.1017/s1743921317010560.
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AbstractObservations at low frequencies (<8GHz) are dominated by distinct direction dependent ionospheric propagation errors, which place a very tight limit on the angular separation of a suitable phase referencing calibrator and astrometry. To increase the capability for high precision astrometric measurements an effective calibration strategy of the systematic ionospheric propagation effects that is widely applicable is required. The MultiView technique holds the key to the compensation of atmospheric spatial-structure errors, by using observations of multiple calibrators and two dimensional interpolation. In this paper we present the first demonstration of the power of MultiView using three calibrators, several degrees from the target, along with a comparative study of the astrometric accuracy between MultiView and phase-referencing techniques. MultiView calibration provides an order of magnitude improvement in astrometry with respect to conventional phase referencing, achieving ~100micro-arcseconds astrometry errors in a single epoch of observations, effectively reaching the thermal noise limit.
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Garbacz, Tomasz, and Ľudmila Dulebova. "Calibration Process and Constructions of Extrusion Calibrators." Key Engineering Materials 635 (December 2014): 135–38. http://dx.doi.org/10.4028/www.scientific.net/kem.635.135.
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In the cellular extrusion process, the extrusion head gives the extrudate the desired cross-section shape and dimensions, taking into account the Barus effect and the shrinkage effect. However, if strict requirements are imposed with regard to cross-section shape and dimensions, it is necessary to fix the shape and dimensions by calibrating the extrudate obtained. The aim of this study is to present methods and constructional solutions of calibration tooling (calibrators) and to present the new calibrator that constitutes a significant element of the adapted and modernized technological extrusion line.
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Elkins, Christopher J., John Fessler, and John K. Eaton. "A Novel Mini Calibrator for Thermochromic Liquid Crystals." Journal of Heat Transfer 123, no. 3 (November 21, 2000): 604–7. http://dx.doi.org/10.1115/1.1370505.
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A small calibrator has been constructed to facilitate wide-band liquid crystal temperature measurements on complex, curved surfaces. The calibrator’s size, 21.3 mm by 20.3 mm by 10.0 mm thick, makes it ideal for in-situ calibrations at multiple sites on curved surfaces. Its design utilizes the heating/cooling ability of a thermoelectric cooler, and its temperature is quickly and accurately controlled by computer. To test the calibrator’s accuracy, a liquid crystal sample was calibrated. Subsequent comparisons to thermistor measurements of a uniform temperature copper block painted with liquid crystals showed the calibration to be accurate to +/−0.1°C between the red start and the approximate blue start temperatures, and the maximum error was less than +/−0.3°C in the dark blue/violet region.
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Sanfelippo, Michael, and Veronica Tillema. "Modified Heparin Assay For The Quantitation Of Rivaroxaban." Blood 122, no. 21 (November 15, 2013): 4814. http://dx.doi.org/10.1182/blood.v122.21.4814.4814.
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The anticoagulant rivaroxaban is not routinely monitored due to its predictable anticoagulant action. However, drug levels are clinically useful in patients requiring surgery as well as in assessing compliance. We have modified a commercial heparin assay based on inhibition of activated factor X (Xa) that was previously modified for the assay of fondaparinux (Am J Clin Pathol 2009, 132:608-612) by replacing the fondaparinux calibrators with commercial rivaroxaban calibration plasmas. Technoview rivaroxaban calibrator plasmas were purchased from Dia Pharma (West Chester, Ohio). These calibrators were substituted for the fondaparinux calibrators. The assay was run on a Siemens BCS XP, as previously described. The assay was linear in the range of 0 to 650 ng/ml. The limit of detection was 14 ng/ml, and carryover at 285 ng/ml was < 1%. The intra-assay precision at 100 ng/ml was standard deviation of 1.04 ng/ml, coefficient of variation of 1.03%. The inter-assay precision at 105 ng/ml was standard deviation 3.5 ng/ml, coefficient of variation of 3.3%. The assay is unaffected by warfarin, but can be affected by other Xa inhibitors such as heparin, low molecular weight heparin, fondaparinux, and apixaban. Disclosures: No relevant conflicts of interest to declare.
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Hegemann, Inga, Karin Koch, Wan Hui Ong Clausen, Mirella Ezban, and Brigitte Brand-Staufer. "Evaluation of N8-GP Activity Using a One-Stage Clotting Assay: A Single-Center Experience." Acta Haematologica 143, no. 5 (October 22, 2019): 504–8. http://dx.doi.org/10.1159/000503377.
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N8-GP (ESPEROCT®; turoctocog alfa pegol; Novo Nordisk A/S, Bagsvaerd, Denmark) is an extended half-life recombinant factor VIII (FVIII) molecule. FVIII-deficient plasma spiked with N8-GP can be accurately measured using many activated partial thromboplastin time (aPTT)-based one-stage clotting assay reagents with normal human plasma calibrators. To date, there are few data on the measurement accuracy of samples from patients treated with N8-GP. Here, we measure patient samples during routine treatment monitoring. Three previously treated patients with severe hemophilia A (HA) without inhibitors (baseline FVIII activity <0.01 IU/mL) received 50 IU/kg N8-GP every fourth day or twice weekly over 5 years as part of the pathfinder2 trial. Patient samples were monitored using the Pathromtin® SL aPTT reagent (Siemens Healthcare GmbH, Erlangen, Germany), a BCS® XP System analyzer (Siemens), and Standard Human Plasma (Siemens) or product-specific calibrators. Patient age ranged from 36 to 62 years. Overall, measurements performed using product-specific or Standard Human Plasma calibrators were in good agreement, with ratios randomly distributed around 1.0. Peak ratios tended to be closer to 1.0 than trough samples. Pathromtin® SL with Standard Human Plasma calibrator consistently and accurately measured FVIII activity in samples from severe HA patients receiving N8-GP prophylaxis.
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Khan, Anuja, Krisjela Shishko, Ryan Marett, Sam Arcidiacono, Vy Nguyen, Genmin Lu, Khanh Bui, Pamela B. Conley, and Anne Winkler. "Analytical Performance of Modified Anti-FXa Assays for Andexanet Alfa-Containing Plasma Samples on the ACL TOP/TOP 50 Coagulation Analyzers." Blood 136, Supplement 1 (November 5, 2020): 5. http://dx.doi.org/10.1182/blood-2020-141006.
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Background: Assay parameters for anti-FXa activity assays for apixaban and rivaroxaban on the ACL TOP/TOP 50 analyzers have been modified to minimize the effect of sample dilution suitable for analyzing andexanet-containing samples with drug-specific calibrators [1].The modified assays showed a dose-dependent reversal of rivaroxaban and apixaban anti-FXa activity in andexanet-containing samples similar to the 96-well format anti-FXa activity assay used in the andexanet clinical studies. In the current study, further assay optimization and verification of analytical performance was performed for the modified apixaban and rivaroxaban assays. Methods: Calibration curves for the modified anti-FXa assays (apixaban, rivaroxaban) were further optimized to improve precision at 100 ng/mL. The calibration curves consisted of 5 dilution levels. The number of replicates at each level was increased from 3 to 4, and outlier removal was enabled to improve the % coefficient of variation (%CV). The limit of blank (LoB), detection (LoD) and quantitation (LoQ) for modified assays on the ACL TOP/TOP 50 were determined in accordance with the minimum requirements of two lots of calibrators and reagent, one instrument system, and three days in accordance with CLSI [2]. The linear ranges were tested for 3 lots of calibrators on 4 analyzers. The samples for the linearity tests consisted of a minimum of 9 to 11 levels extending below and above the anticipated linear range. A 5-day precision was performed with diluted controls encompassing the modified assay calibration range and andexanet-containing samples on a minimum of two analyzers with one lot of drug-specific calibrator to verify analytical performance. Results: Analytical performance with optimized calibration settings was evaluated with a minimum of 9 calibration curves generated with 3 calibrator lots and demonstrated improvement in the r2 and %CV at each level. The analytical parameters for the modified apixaban assay generated with 3 lots of calibrator and reagent on 4 analyzers are as follows: LoB of ~2.1 ng/mL, LoD of 3.5 ng/mL, and LoQ of 5.9 ng/mL. The analytical parameters for the modified rivaroxaban assay were generated with 2 lots of calibrators and reagents with a LoB of 2.3 ng/mL, and LoD of 3.6 ng/mL. Three lots of calibrators and reagents were used to generate an LoQ of 5.4 ng/mL. The linear range was determined to be 10-100 ng/mL and met the acceptance criteria for r2≥ 0.95 and slope of 0.90 - 1.10 for both assays. Conclusions: Results of this study demonstrate that modified apixaban and rivaroxaban LoQ and linearity meet the assay requirements. Modified test parameters will be user-defined on the ACL TOP/TOP 50 analyzers and can be used to measure apixaban or rivaroxaban levels when andexanet is present in the samples. References: Khan, A. et al. Blood(2019) 134 (Supplement1): 1153. American Society of Hematology- Modified Anti-FXa assays for measuring the residual activity of apixaban and rivaroxaban in andexanet alfa-containing samples on the ACL TOP Family® coagulation analyzers. CLSI EP17-A2.Evaluation of Detection Capability for Clinical Laboratory Measurement Procedures; Approved Guideline - Second Edition.Wayne, PA: Clinical and Laboratory Standards Institute; 2012. Disclosures Lu: Portola Pharmaceuticals, Inc.:Current Employment.Bui:Portola Pharmaceuticals, Inc,:Current Employment.Conley:Portola Pharmaceuticals, Inc.:Current Employment.
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Heywood, I., E. Lenc, P. Serra, B. Hugo, K. W. Bannister, M. E. Bell, A. Chippendale, et al. "Field sources near the southern-sky calibrator PKS B1934-638: effect on spectral line observations with SKA-MID and its precursors." Monthly Notices of the Royal Astronomical Society 494, no. 4 (April 11, 2020): 5018–28. http://dx.doi.org/10.1093/mnras/staa941.
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ABSTRACT Accurate instrumental bandpass corrections are essential for the reliable interpretation of spectral lines from targeted and survey-mode observations with radio interferometers. Bandpass correction is typically performed by comparing measurements of a strong calibrator source to an assumed model, typically an isolated point source. The wide field-of-view and high sensitivity of modern interferometers means that additional sources are often detected in observations of calibrators. This can introduce errors into bandpass corrections and subsequently the target data if not properly accounted for. Focusing on the standard calibrator PKS B1934-638, we perform simulations to asses this effect by constructing a wide-field sky model. The cases of ASKAP (0.7–1.9 GHz), MeerKAT (UHF: 0.58–1.05 GHz; L-band: 0.87–1.67 GHz) and Band 2 (0.95–1.76 GHz) of SKA-MID are examined. The use of a central point source model during bandpass calibration is found to impart amplitude errors into spectra measured by the precursor instruments at the ∼0.2–0.5 per cent level dropping to ∼0.01 per cent in the case of SKA-MID. This manifests itself as ripples in the source spectrum, the behaviour of which is coupled to the distribution of the array baselines, the solution interval, the primary beam size, the hour-angle of the calibration scan, as well as the weights used when imaging the target. Calibration pipelines should routinely employ complete field models for standard calibrators to remove this potentially destructive contaminant from the data, a recommendation we validate by comparing our simulation results to a MeerKAT scan of PKS B1934-638, calibrated with and without our expanded sky model.
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Rohde, Gabriele, Gertrud Stratmann, Christian Hesse, Natalie Herth, Stephan Schwers, Elisabeth Perzborn, Edelgard Lindhoff-Last, and Helen Mani. "Accurate determination of rivaroxaban levels requires different calibrator sets but not addition of antithrombin." Thrombosis and Haemostasis 108, no. 07 (2012): 191–98. http://dx.doi.org/10.1160/th11-12-0832.
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SummaryRivaroxaban is a direct factor Xa inhibitor, which can be monitored by anti-factor Xa chromogenic assays. This ex vivo study evaluated different assays for accurate determination of rivaroxaban levels. Eighty plasma samples from patients receiving rivaroxaban (Xarelto®) 10 mg once daily and 20 plasma samples from healthy volunteers were investigated using one anti-factor Xa assay with the addition of exogenous antithrombin and two assays without the addition of antithrombin. Two different lyophilised rivaroxaban calibration sets were used for each assay (low concentration set: 0, 14.5, 59.6 and 97.1 ng/ml; high concentration set: 0, 48.3, 101.3, 194.2 and 433.3 ng/ml). Using a blinded study design, the rivaroxaban concentrations determined by the assays were compared with concentrations measured by HPLC-MS/MS. All assays showed a linear relationship between the rivaroxaban concentrations measured by HPLC-MS/MS and the optical density of the anti-FXa assays. However, the assay with the addition of exogenous anti-thrombin detected falsely high concentrations of rivaroxaban even in plasma samples from controls who had not taken rivaroxaban (intercept values using the high calibrator set and the low calibrator set: +26.49 ng/ml and +13.71 ng/ml, respectively). Plasma samples, initially determined by the high calibrator setting and containing rivaroxaban concentrations <25 ng/ml, had to be re-run using the low calibrator setting for precise measurement. In conclusion, anti-factor Xa chromogenic assays that use rivaroxaban calibrators at different concentration levels can be used to measure accurately a wide range of rivaroxaban concentrations ex vivo. Assays including exogenous antithrombin are unsuitable for measurement of rivaroxaban.
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Gupta, A., S. F. Shariat, J. A. Eastham, P. T. Scardino, A. J. Vickers, and H. Lilja. "The knowledge and practices of urologists in the United States (US) about standardization of PSA assays." Journal of Clinical Oncology 29, no. 7_suppl (March 1, 2011): 207. http://dx.doi.org/10.1200/jco.2011.29.7_suppl.207.
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207 Background: PSA assays can be calibrated to either the WHO or the Hybritech standard. Studies of PSA-based prostate cancer screening have used Hybritech-standardized assays and prostate cancer risk calculators are based on these studies. Testing of patient samples with a WHO calibrated assay gives values that are 22% lower than from those with Hybritech-calibrated assays. Up to 60% of the labs in the US use WHO calibrated assays. We evaluated whether US urologists are aware of the different calibrators and the differences in PSA values. Methods: A random sample of 1,742 US urologists were invited by email to participate in a web-based survey of their knowledge and practices regarding PSA assay standardization. No mention was made of assays or calibration in the invitation. 419 responses were received. Results: Many (56%) US urologists thought that different standards may lead to clinically relevant differences in PSA values. Although 62% reported awareness of the two PSA calibrators, 67% did not know the difference between the two. Only 17% correctly reported the difference between the two standards. Nationally almost 60% of the labs use WHO standardized assays, but in this survey only 5% of the urologists thought that the hospital where they practice used a WHO standardized assay. The rest reported either not knowing the standard (46%) or use of the Hybritech standard (49%). The majority of urologists did not look at the reference range (64%) or for the PSA standard (74%) in the lab reports. Only 25% reported considering the PSA-calibration in their clinical decisions about prostate biopsy, but only a third of them correctly knew the difference between the calibrators. Conclusions: Many US urologists are unaware of the difference caused by WHO versus Hybritech based PSA-assay calibration. Although 60% of clinical laboratories use WHO-calibrated assays, only 5% of urologists are aware of this use in their practice, and a majority of urologists could not correctly explain the difference between the different calibrators. A greater awareness is needed amongst US urologists about the different PSA calibrators, the calibrator in use at their practice, and means to account for different calibrators in clinical decision making. [Table: see text]
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Brister-Smith, Allister, Jeffrey A. Young, and Alec Saitman. "A 24-Hour Extended Calibration Strategy for Quantitating Tacrolimus Concentrations by Liquid Chromatography–Tandem Mass Spectrometry." Journal of Applied Laboratory Medicine 6, no. 5 (June 17, 2021): 1293–98. http://dx.doi.org/10.1093/jalm/jfab048.
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Abstract Background Tacrolimus has a low therapeutic index requiring strict control of whole blood concentrations. Although random access immunoassay platforms exist that rapidly provide quantitative values for tacrolimus, LC–MS/MS may provide more accurate quantitation. However, batch testing in many LC–MS/MS assays is not efficient, particularly when testing patients suspected of having tacrolimus toxicity. Extending calibration curve stability beyond the traditionally accepted single batch may facilitate improved turnaround time and reduce testing costs. A 24-h extended calibration of LC–MS/MS tacrolimus was designed and validated to reduce calibrator usage, improve turnaround time, and provide a more efficient workflow for urgent requests. Methods Patient samples included in the study were extracted and assayed with coextracted calibrators and quality control in real time. The same patient samples were extracted again 24 h later without coextracted calibrators. The data acquired from the second patient sample extraction was applied to the original calibration curve acquired 24 h prior and compared to the data for the same samples coextracted with calibrators, creating a value set utilizing extended curve stability. Results A linear regression compared the results using the extended curve to the results of the coextracted acquisitions. This yielded a strong correlation between the 2 data populations, with a slope of 1.0061 and a correlation coefficient of >0.95. The average bias between original patient values and patient values 24 h later was 3.4% across all patient samples. Conclusions Patient tacrolimus values were comparable when extracted within 24 h of calibration versus values coextracted with calibrators. Demonstrating comparability within 24 h of calibration allows the laboratory to provide rapid turnaround time for urgent samples without the need for an entirely new calibration curve.
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Li, Liang, Gukun Liu, Jun Hong, Feng Ming, and Yu Wang. "Design and Implementation of a Multi-Band Active Radar Calibrator for SAR." Remote Sensing 11, no. 11 (June 1, 2019): 1312. http://dx.doi.org/10.3390/rs11111312.
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Over the past decade, IECAS (Institute of Electronics, Chinese Academy of Sciences) has developed a set of L-, S-, C-, and X-band active radar calibrators that are deployed during the calibration campaigns for HJ1C synthetic aperture radar (SAR), Gaofen-3 SAR, and so on. In the near future, P-band and Ka-band spaceborne SARs will be launched. We found that it is not convenient to develop special active radar calibrators (ARCs) for a specific SAR or a specific frequency band SAR, and the acquired experience could help in the design and development of a multi-band ARC. This paper describes the design and implementation of a multi-band active radar calibrator which can operate in the L-, C-, X-, and Ka-bands. Moreover, laboratory measurements are performed to characterize the performance of the multi-band ARC, paying particular attention to the gain stability, the system transfer function, the gain flatness, and the linearity of the ARC receiver. Three such ARCs are developed, and to our knowledge, the multi-band ARC is the first of its kind in China or even in the world, and it can be used to implement the calibration campaigns of the Chinese Gaofen-3 SAR, Shenzhen-1 SAR, Luojia-2 SAR, and so on.
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Gille, Benjamin, Lieselot Dedeene, Erik Stoops, Leentje Demeyer, Cindy Francois, Stefanie Lefever, Maxim De Schaepdryver, et al. "Automation on an Open-Access Platform of Alzheimer’s Disease Biomarker Immunoassays." SLAS TECHNOLOGY: Translating Life Sciences Innovation 23, no. 2 (January 18, 2018): 188–97. http://dx.doi.org/10.1177/2472630317750378.
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The lack of (inter-)laboratory standardization has hampered the application of universal cutoff values for Alzheimer’s disease (AD) cerebrospinal fluid (CSF) biomarkers and their transfer to general clinical practice. The automation of the AD biomarker immunoassays is suggested to generate more robust results than using manual testing. Open-access platforms will facilitate the integration of automation for novel biomarkers, allowing the introduction of the protein profiling concept. A feasibility study was performed on an automated open-access platform of the commercial immunoassays for the 42-amino-acid isoform of amyloid-β (Aβ1–42), Aβ1–40, and total tau in CSF. Automated Aβ1–42, Aβ1–40, and tau immunoassays were performed within predefined acceptance criteria for bias and imprecision. Similar accuracy was obtained for ready-to-use calibrators as for reconstituted lyophilized kit calibrators. When compared with the addition of a standard curve in each test run, the use of a master calibrator curve, determined before and applied to each batch analysis as the standard curve, yielded an acceptable overall bias of −2.6% and −0.9% for Aβ1−42 and Aβ1–40, respectively, with an imprecision profile of 6.2% and 8.4%, respectively. Our findings show that transfer of commercial manual immunoassays to fully automated open-access platforms is feasible, as it performs according to universal acceptance criteria.
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Petrovic, Goran, Juraj Alojzije Bosnic, Goran Majic, and Marin Despalatovic. "A Design of PWM Controlled Calibrator of Non-Sinusoidal Voltage Waveforms." Energies 12, no. 10 (May 23, 2019): 1966. http://dx.doi.org/10.3390/en12101966.
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Power quality conditions in electrical power networks have drastically changed in recent years. A number of electrical devices and power generators that are the main sources of disturbances is ever increasing. Thus, the need for calibrators of different electrical equipment that will be able to generate non-sinusoidal voltages and/or currents has proportionally increased. This paper presents a simple, unconventional approach of generating voltage harmonics, which do not rely on digital-to-analog (D/A) boards and power amplifier to amplify low-voltage signals. A fundamental part of the calibrator is the insulated gate bipolar transistor (IGBT) inverter with low-pass LRC filter at its output, which eliminates higher harmonics from the generated voltage. Desired voltage waveform is directly generated at the inverter’s output, thus the power amplifier is omitted from the setup. The modulation technique used for controlling IGBTs is the well-known sine pulse width modulation (PWM). Magnitudes and phase angles of the desired harmonics are regulated to compensate for the phenomena that may have a negative influence on their values: Nonlinearities of the system, temperature variation, voltage drops on parasitic components, etc. Experimental results show great potential of the proposed method for the design of the voltage calibrator for various electrical instruments.
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Vallie, S., and S. Naidoo. "Quality Assurance in Drug Assaying and Pharmacokinetics-Blood Protein Evaluation in Calibration Curves." International Journal of Pharmaceutical Quality Assurance 11, no. 01 (March 25, 2020): 45–52. http://dx.doi.org/10.25258/ijpqa.11.1.7.
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In bioanalytical drug assays, plasma protein/albumin content can challenge the biomatrix and reduce drug recovery through the albumin-binding affinity (ABA) of drug molecules. Global quality assurance in sample preparation for analyte quantification during bioavailability assessments has evolved extensively, and the quality standards of the strictly regulated current global quality controlled drug manufacturing processes (cGQMP) now apply in pharmacokinetics (PK) studies. Previous analyses in large clinical trials had found that laboratory-prepared calibrator plasma/serum protein levels differed significantly from those of patients with occasional hyperproteinemia/hypoproteinemia and disease-related hyperalbuminemia/hypoalbuminemia. We, therefore, investigated improving assay accuracy by including adjustments for patient plasma/serum protein levels in protein evaluation calibrations curves (PROTEC). Using a combined PROTEC of two calibrators (with 1.6 ± 0.5 g/dL and 4.3g/dL albumin, respectively) to test rifampicin recovery from patients with hypoalbuminemia (1.6 ± 0.5 g/dL), we found that relative accuracy of drug recovery differed by minimum 0.1% for low ABA drugs and maximum >20% for moderate ABA drugs. Assay accuracy improved after accommodating for varying patient plasma/serum protein levels. We, therefore, propose using patient-calibrator PROTEC-PK in validation assay development/therapeutic drug monitoring to ensure that patient albumin levels are within acceptable validation accuracy ranges.
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Li, Xiang, Litao Yang, Jianzhong Zhang, Shu Wang, Kailin Shen, Liangwen Pan, and Dabing Zhang. "Simplex and Duplex Polymerase Chain Reaction Analysis of Herculex® RW (59122) Maize Based on One Reference Molecule Including Separated Fragments of 5 Integration Site and Endogenous Gene." Journal of AOAC INTERNATIONAL 92, no. 5 (September 1, 2009): 1472–83. http://dx.doi.org/10.1093/jaoac/92.5.1472.
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Abstract Reference molecules, as positive controls and calibrators, have been recently developed in genetically modified organism analysis as a potential substitute for reference materials derived from plant raw materials. In this study, a novel reference molecule p59122, including the revealed 5 integration sequence of maize Herculex® RW (59122), was constructed that was suitable for simplex and duplex event-specific qualitative and quantitative PCR detections. The LOD values were 10 copies both for simplex and duplex qualitative PCR when p59122 was used as the calibrator. These values were comparable to those of using genomic DNA samples with 0.01 and 0.05, approximately 5 and 25 hyploid genomic DNA copies, respectively. The absolute LOD and LOQ values were confirmed to be as low as 10 and 25 copies of p59122 DNA both in simplex and duplex quantitative systems. Furthermore, ideal quantification data with low bias, SD and RSD values were obtained from the practical samples analyses in simplex and duplex real-time PCR systems using the reference molecule p59122 as a calibrator. All these results suggested that the developed reference molecule p59122 and the qualitative and quantitative PCR detection methods are suitable for identification and quantification of GM maize 59122 and its derived products.
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Filípek, Jaroslav, and Josef Illek. "Serum albumin assay – easy or problematic analysis?" Acta Veterinaria Brno 89, no. 4 (2020): 301–5. http://dx.doi.org/10.2754/avb202089040301.
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Serum albumin determination is an important biochemical investigation in clinical laboratories. Photometric methods using albumin binding to organic dyes – bromocresol green (BCG) or bromocresol purple (BCP) – are most commonly used. These determinations are quick, simple, and inexpensive. They are, however, associated with a number of problems. Discussions on the methodological unification and use of BCP are ongoing in human laboratory medicine. The reaction of human albumin with this dye is more specific. On the other hand, its affinity for animal albumin is significantly lower, for which reason BCG is used in veterinary medicine. However, due to the lower reaction specificity of this dye, the results are slightly overestimated as the dye reacts to a lesser extent with alpha and beta globulins. This disadvantage can be largely eliminated by reducing the incubation time to about 30 s. Another problem is the method calibration. Some laboratories use species-specific albumin as calibrators, but this is technically challenging for a laboratory that analyzes albumin of many species. We therefore recommend using a commercially available calibrator that is traceable to the European Reference Material for Specific Proteins. We consider these following principles – using BCG, shortening the incubation time to 30 s and using the mentioned calibrator – as a basic condition to obtain clinically correct and inter-laboratory comparable results.
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Wang, Caroline C., Eric E. Petty, and Christopher M. Smith. "Rapid and Efficient Analysis of Microcystins, Nodularin, Cylindrospermopsin, and Anatoxin-a in Drinking Water by LC Tandem MS." Journal of AOAC INTERNATIONAL 99, no. 6 (November 1, 2016): 1565–71. http://dx.doi.org/10.5740/jaoacint.16-0143.
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Abstract A fast and sensitive LC-MS method was developed for the simultaneous analysis of 11 cyanotoxins in drinking water. The toxins in this method included eight microcystins, as well as nodularin, anatoxin-a, and cylindrospermopsin. Sample processing involved a small sample volume and a direct dilution procedure that could be performed in minutes rather than hours using traditional SPE procedures. This method also featured a short acquisition time of 12 min with an adequate separation of all analytes. Validation results demonstrated good sensitivity with LODs <100 ng/L and good precision (RSD < 20%) and accuracy. Analyte stability was also thoroughly studied. The matrix effect was minimal, and tap water used for calibrators and controls. No sample carryover was observed after the highest concentration calibrator.
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Gupta, M. "Accurate Simulation of the Four Modes of Post-Die Extrudate Shape Distortion." International Polymer Processing 36, no. 1 (March 1, 2021): 69–78. http://dx.doi.org/10.1515/ipp-2020-3995.
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Abstract A combined flow, thermal and structural analysis is employed to simulate post-die extrudate distortion in different profile dies. All four factors which can cause extrudate distortion, namely, nonuniform exit velocity distribution, extrudate shrinkage, extrudate draw down, and deformed shape of the calibrator or sizer profile, are simulated. To analyze the effect of exit velocity variation on extrudate distortion, the parameterized geometry of a simple profile die is optimized using an extrusion die optimization software. The simulation results presented for a bi-layer profile die successfully demonstrate how gradually changing profile shape in successive calibrators/sizers can be used to simplify the die design for extrusion of complex profiles. The predicted extrudate shape and layer structure for the bi-layer die are found to accurately match with those in the extruded product.
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Asadina, Habliya, Torib Hamzah, Dyah Titisari, and Bedjo Utomo. "A Centrifuge Calibrator Based on Personal Computer Equipped with Data Processor." Indonesian Journal of electronics, electromedical engineering, and medical informatics 1, no. 1 (August 22, 2019): 14–19. http://dx.doi.org/10.35882/ijeeemi.v1i1.3.
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Calibration is an activity to determine the conventional truth of the value of the appointment of a measuring instrument by comparing traceable standards to national and international standards for measurement and / or international units and certified reference materials. The purpose of this study is to develop a system of efficient and practical centrifuge calibrators by sending the calibration results directly via bluetooth to a PC. The main series of centrifuge calibrators are Arduino modules, laser sensors and Bluetooth.The high low signal is obtained from the reflection of the laser beam aimed at the reflector point on the centrifuge plate, processed in the Arduino module and displayed on the LCD, the calibration results can be directly seen in the Delphi program. The design of this module is also equipped with a Bluetooth transmitter to send data to a PC. This module can be used in medical equipment calibration laboratories. Based on the results of testing and data collection on the 8 Tube centrifuge with a Lutron Tachometer ratio, the error value was 0.0136%. After planning, experimenting, making modules, testing modules, and collecting data, it can be concluded that the tool "centrifuge calibrator equipped with PC-based data processors" can be used and according to planning because the fault tolerance does not exceed 10%.Keywords—Holter Monitor; Heart Monitoring; Arduino Microcontroller; SD Card Memory
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Monti-Guarnieri, Andrea, Paolo Falcone, Davide d’Aria, and Giuseppe Giunta. "3D Vibration Estimation from Ground-Based Radar." Remote Sensing 10, no. 11 (October 23, 2018): 1670. http://dx.doi.org/10.3390/rs10111670.
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The paper proposes a method to estimate 2D/3D vibrations and displacements of mostly linear structures, like pipes, chimneys, towers, bridges from afar, based on synchronized Radars. The method takes advantage of Radar sensitivity to displacements to sense tiny deformations (up to tens of micron) with a time scale from milliseconds to hours. The key elements are: (a) The use of calibrators to remove at once both the tropospheric turbulence and the effect of radial motion, and (b) the compensation of interferences from fixed targets. The latter is performed by estimating and removing the contribution of interfering targets, based either on a proper data processing or by exploiting an ad-hoc motorized calibrator. Performance in terms of accuracy of the deformation field is evaluated theoretically and checked by tests carried out in laboratories and by full-scale acquisition campaigns.
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Tate, Jillian R., Nader Rifai, Kåre Berg, Rémy Couderc, Francesco Dati, Gert M. Kostner, Ikunosuke Sakurabayashi, and Armin Steinmetz. "International Federation of Clinical Chemistry standardization project for the measurement of lipoprotein(a). Phase I. Evaluation of the analytical performance of lipoprotein(a) assay systems and commercial calibrators." Clinical Chemistry 44, no. 8 (August 1, 1998): 1629–40. http://dx.doi.org/10.1093/clinchem/44.8.1629.
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Abstract A secondary reference material for lipoprotein(a) is required to standardize the measurement of lipoprotein(a) in clinical laboratories worldwide. Towards this aim, the International Federation of Clinical Chemistry Working Group for the Standardization of Lipoprotein(a) Assays has initiated a standardization project involving a total of 33 diagnostic company and clinical chemistry laboratories from 12 countries. In Phase 1, the analytical performance of 40 lipoprotein(a) assay systems was evaluated by testing sera and manufactured lipoprotein(a) calibrator materials for precision, linearity, and parallelism. Twenty test systems were nonoptimized according to the results for a pooled serum, which tested nonlinear in 16 systems and imprecise in 4. Acceptable analytical properties and harmonization of lipoprotein(a) values were shown by some commercial calibrators, suggesting their possible use as reference materials. This study highlights the problems that currently occur for lipoprotein(a) measurement in existing assay systems.
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Olencki, Andrzej, and Piotr Mróz. "Testing Of Energy Meters Under Three-Phase Determined And Random Nonsinusoidal Conditions." Metrology and Measurement Systems 21, no. 2 (June 1, 2014): 217–32. http://dx.doi.org/10.2478/mms-2014-0019.
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Abstract Electric energy meters are designed to account energy under sinusoidal and nonsinusoidal conditions, because both, old and new standards for energy meters require testing their accuracy under different conditions. The latest EN 50470 standard increases the range of meter testing under nonsinusoidal conditions, introducing new shapes of test signals such as the phase fired waveform or the burst fired waveform. This paper discusses calibration problems of electronic revenue energy meters for direct connection and for connection through current transformers, and it proposes a new calibration procedure which reproduces normal operating conditions better: three-phase configurations of measurement systems, load range during meter testing or shapes of test signals. Recently, modern Electrical Power Standards, also known as Power Calibrators, enable automatic testing of various types of electrical devices, including electricity meters in their normal operating conditions. This article presents examples of single and multi position fully automatic test systems, which employ Power/Energy Calibrator from Poland as the precision source with programmed waveforms of three phase voltages up to 560 V and currents up to 120 A conforming to EN 50470, or with random waveforms generated by PC software random wave generator. Measurement uncertainty of the energy meters under different nonsinusoidal conditions using a test system with reference to accuracy of the power calibrator or to the reference meter, are discussed. Comparative analysis of test results for different shapes of voltage and current signals is presented in the conclusions of this paper.
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Cruzalèbes, P., R. G. Petrov, S. Robbe-Dubois, J. Varga, L. Burtscher, F. Allouche, P. Berio, et al. "A catalogue of stellar diameters and fluxes for mid-infrared interferometry★." Monthly Notices of the Royal Astronomical Society 490, no. 3 (October 7, 2019): 3158–76. http://dx.doi.org/10.1093/mnras/stz2803.
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Abstract We present the Mid-infrared stellar Diameters and Fluxes compilation Catalogue (MDFC) dedicated to long-baseline interferometry at mid-infrared wavelengths (3–13 $\mu$m). It gathers data for half a million stars, i.e. nearly all the stars of the Hipparcos-Tycho catalogue whose spectral type is reported in the SIMBAD data base. We cross-match 26 data bases to provide basic information, binarity elements, angular diameter, magnitude and flux in the near and mid-infrared, as well as flags that allow us to identify the potential calibrators. The catalogue covers the entire sky with 465 857 stars, mainly dwarfs and giants from B to M spectral types closer than 18 kpc. The smallest reported values reach 0.16 $\mu$Jy in L and 0.1 $\mu$Jy in N for the flux, and 2 microarcsec for the angular diameter. We build four lists of calibrator candidates for the L and Nbands suitable with the Very Large Telescope Interferometer (VLTI) sub- and main arrays using the MATISSE instrument. We identify 1621 candidates for L and 44 candidates for N with the Auxiliary Telescopes (ATs), 375 candidates for both bands with the ATs, and 259 candidates for both bands with the Unit Telescopes (UTs). Predominantly cool giants, these sources are small and bright enough to belong to the primary lists of calibrator candidates. In the near future, we plan to measure their angular diameter with 1 per cent accuracy.
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ABNIZOVA, IRINA, TOM SKELLY, FEDOR NAUMENKO, NAVA WHITEFORD, CLIVE BROWN, and TONY COX. "STATISTICAL COMPARISON OF METHODS TO ESTIMATE THE ERROR PROBABILITY IN SHORT-READ ILLUMINA SEQUENCING." Journal of Bioinformatics and Computational Biology 08, no. 03 (June 2010): 579–91. http://dx.doi.org/10.1142/s021972001000463x.
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As was the case in the beginning of the sequencing era, the new generation of short-read sequencing technologies still requires both accuracy of data processing methods and reliable measures of that accuracy. Inspired by the classic of the genre, the Phred method, we generalized those findings in the area of base quality value calibration. We introduce a simple, straightforward statistically established way to measure the performance of a calibrator, and to find an optimal way to assess its reliability. We illustrate the method by assessing the performance of several calibrators/predictors for Illumina, Genome Analyser 2 (GA2) data. The choice of the best predictor is based on optimization of validity, discriminative ability and discrimination power for several candidate predictors. We applied the method on data from one experimental run for genome of the phage ϕX, and found the best predictor out of ten candidates to be 'Purity', a statistics derived from corrected cluster intensities. The source code for the comparison of the predictors is available from the authors by request.
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Tormey, W. P., and P. A. O'Brien. "Clinical Associations of an Increased Transthyretin Band in Routine Serum and Urine Protein Electrophoresis." Annals of Clinical Biochemistry: International Journal of Laboratory Medicine 30, no. 6 (November 1993): 550–54. http://dx.doi.org/10.1177/000456329303000604.
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The 9697 electrophoretograms performed over an 8 year period were reviewed to identify the frequency and clinical associations of the finding of a prominent transthyretin band in serum or urine, the concentration of which was equal to or greater than a 64 mg/dL protein calibrator. All samples were electrophoresed at a constant 90 V using agarose gels with a barbital buffer pH 8·6 and Ponceau S staining. Reference calibrators were used as standards to identify increased transthyretin bands and the patients' clinical records were subsequently reviewed. High values were found in 46 patients' sera and a further nine patients' urines representing 0·57% of the total workload. Renal impairment was present in 58% of cases including those with chronic renal failure, the nephrotic syndrome and paraproteinaemia. The high levels were not persistent in three myeloma cases where there was a recovery in renal function following chemotherapy. In some nephrotics, a high urine transthyretin may be secondary to a general hepatic albumin and transport protein synthesis response to severe proteinuria. Why the serum transthyretin was elevated in many other cases remains unclear.