Total cholesterol performance of Abell–Levy–Brodie–Kendall reference measurement procedure: Certification of Japanese in-vitro diagnostic assay manufacturers through CDC's Cholesterol Reference Method Laboratory Network

Background: In-vitro diagnostic (IVD) bilirubin reagents based on oxidation with bilirubin oxidase (BOX) or vanadic acid (VA) for total and direct-reacting bilirubin (TB and DB) are widely used in Japan; however, their reactivity to unconjugated and conjugated bilirubin (UCB and CB) and delta bilirubin (DLB) has not been completely disclosed by manufacturers. We used artificially prepared bilirubin materials to investigate the reactivity with four IVD bilirubin reagents. Methods: Porcine UCB solution, chemically synthesized ditaurobilirubin (DTB) solution, and chemically synthesized DLB solution were used as surrogates of naturally occurring UCB, CB, and DLB, respectively. The TB and DB concentrations were measured by three BOX methods and one VA method, and the observed concentrations were compared with those obtained by the diazo-based reference measurement procedure (RMP). Results: The UCB and DLB concentrations were similar when any of the four IVD bilirubin reagents were used during TB measurement. This was consistent with RMP and exhibited a converged inter-method variation. Compared with RMP, significantly low DTB concentrations were observed by the IVD bilirubin reagents despite the converged inter-method variation. In DB measurement, some reagents reacted doubtfully with UCB, while showed lower DTB concentrations than its corresponding TB concentration. Reactivity with DLB was different for each method including RMP. Some reagents were developed to react less with DLB and others to strongly react with DLB. Conclusions: We revealed the reactivity of IVD-TB and IVD-DB reagents to artificially prepared bilirubin materials, and their consistency with RMP. The DB data results vary depending on the reagents used.

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A Reference Method Laboratory Network for Cholesterol: A Model for Standardization and Improvement of Clinical Laboratory Measurements

Clinical Chemistry ◽

10.1093/clinchem/46.11.1762 ◽

2000 ◽

Vol 46 (11) ◽

pp. 1762-1772 ◽

Cited By ~ 102

Author(s):

Gary L Myers ◽

Mary M Kimberly ◽

Parvin P Waymack ◽

S Jay Smith ◽

Gerald R Cooper ◽

...

Keyword(s):

Reference Materials ◽

Clinical Laboratory ◽

Matrix Effects ◽

Reference Method ◽

Performance Criteria ◽

Blood Cholesterol ◽

Field Methods ◽

Laboratory Network ◽

In Vitro Diagnostic

Abstract Background: Accurate and precise measurement of blood cholesterol plays a central role in the National Cholesterol Education Program’s strategy to reduce the morbidity and mortality attributable to coronary heart disease. Matrix effects hamper the ability of manufacturers to adequately calibrate and validate traceability to the National Reference System for Cholesterol (NRS/CHOL). CDC created the Cholesterol Reference Method Laboratory Network (CRMLN) to improve cholesterol measurement by assisting manufacturers of in vitro diagnostic products with validation of the traceability of their assays to the NRS/CHOL. Methods: CRMLN laboratories established the CDC cholesterol reference method (modification of the Abell-Levy-Brodie-Kendall chemical method) and are standardized using CDC frozen serum reference materials. CRMLN laboratories use common quality-control materials and participate in monthly external performance evaluations conducted by CDC. The CRMLN performance criteria require member laboratories to agree with CDC within ± 1.0% and maintain a CV ≤2.0%. Results: From 1995 to 2000, the CRMLN laboratories met the accuracy criterion 97% of the time and the precision criterion 99% of the time. During this time period, the CRMLN maintained an average bias to CDC of 0.01% and an average collective CV of 0.33%. Conclusions: CDC established the CRMLN as the first international reference method laboratory network. The CRMLN assists manufacturers in the validation of the calibration of their diagnostic products so that clinical laboratories can measure blood cholesterol more reliably. The CRMLN can serve as a model for other clinical analytes where traceability to a hierarchy of methods is needed and matrix effects of the field methods with processed calibrators or reference materials are present.

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Toward standardization of carbohydrate-deficient transferrin (CDT) measurements: II. Performance of a laboratory network running the HPLC candidate reference measurement procedure and evaluation of a candidate reference material

Clinical Chemistry and Laboratory Medicine (CCLM) ◽

10.1515/cclm.2010.322 ◽

2010 ◽

Vol 48 (11) ◽

Cited By ~ 34

Author(s):

Anders Helander ◽

Jos P.M. Wielders ◽

Jan-Olof Jeppsson ◽

Cas Weykamp ◽

Carla Siebelder ◽

...

Keyword(s):

Reference Material ◽

Measurement Procedure ◽

Reference Measurement ◽

Candidate Reference Material ◽

Laboratory Network ◽

Reference Measurement Procedure ◽

Carbohydrate Deficient Transferrin

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Proposed Serum Cholesterol Reference Measurement Procedure by Gas Chromatography–Isotope Dilution Mass Spectrometry

Clinical Chemistry ◽

10.1373/clinchem.2010.158766 ◽

2011 ◽

Vol 57 (4) ◽

pp. 614-622 ◽

Cited By ~ 30

Author(s):

Selvin H Edwards ◽

Mary M Kimberly ◽

Susan D Pyatt ◽

Shelton L Stribling ◽

Kara D Dobbin ◽

...

Keyword(s):

Mass Spectrometry ◽

Gas Chromatography ◽

Serum Cholesterol ◽

Isotope Dilution ◽

Isotope Dilution Mass Spectrometry ◽

Measurement Procedure ◽

Standard Reference Materials ◽

Reference Measurement ◽

Reference Measurement Procedure ◽

The Mean

BACKGROUND Our purpose was to establish a mass spectrometry reference measurement procedure (RMP) for cholesterol to use in the CDC's standardization programs. We explored a gas chromatography–isotope dilution mass spectrometry (GC-IDMS) procedure using a multilevel standard calibration curve to quantify samples with varying cholesterol concentrations. METHODS We calibrated the mass spectrometry instrument by isotope dilution with a pure primary standard reference material and an isotopically enriched cholesterol analog as the internal standard (IS). We diluted the serum samples with Tris-HCl buffer (pH 7.4, 0.05 mol/L, 0.25% Triton X-100) before analysis. We used 17 serum pools, 10 native samples, and 2 standard reference materials (SRMs). We compared the GC-IDMS measurements with the CDC's modified Abell–Levy–Brodie–Kendall (AK) RMP measurements and assessed method accuracy by analyzing 2 SRMs. We evaluated the procedure for lack of interference by analyzing serum spiked with a mixture of 7 sterols. RESULTS The mean percent bias between the AK and the GC-IDMS RMP was 1.6% for all samples examined. The mean percent bias from NIST's RMP was 0.5% for the SRMs. The total %CVs for SRM 1951b levels I and II were 0.61 and 0.73%, respectively. We found that none of the sterols investigated interfered with the cholesterol measurement. CONCLUSIONS The low imprecision, linear response, lack of interferences, and acceptable bias vs the NIST primary RMP qualifies this procedure as an RMP for determining serum cholesterol. The CDC will adopt and implement this GC-IDMS procedure for cholesterol standardization.

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Verification of Low-Density Lipoprotein Cholesterol Levels Measured by Anion-Exchange High-Performance Liquid Chromatography in Comparison with Beta Quantification Reference Measurement Procedure

The Journal of Applied Laboratory Medicine ◽

10.1093/jalm/jfaa144 ◽

2020 ◽

Author(s):

Daisuke Manita ◽

Hiroshi Yoshida ◽

Isao Koyama ◽

Masakazu Nakamura ◽

Yuji Hirowatari

Keyword(s):

Anion Exchange ◽

Clinical Laboratory ◽

Measurement Procedure ◽

Calculation Methods ◽

Serum Samples ◽

Cvd Risk ◽

Blood Samples ◽

Reference Measurement ◽

Reference Measurement Procedure ◽

Homogeneous Assays

Abstract Background A new lipoprotein testing method based on anion-exchange HPLC (AEX-HPLC) was recently established. We verified the accuracy of LDL-C levels, a primary therapeutic target for the prevention of cardiovascular disease (CVD), measured by AEX-HPLC comparing with LDL-C levels measured by beta quantification-reference measurement procedure (BQ-RMP), homogenous assays, and calculation methods. Methods We compared LDL-C levels measured by AEX-HPLC (adLDL-Ch: LDL-Ch and IDL-Ch) and BQ-RMP using blood samples from 52 volunteers. AdLDL-Ch levels were also compared with those measurements by homogeneous assays and calculation methods (Friedewald equation, Martin equation, and Sampson equation) using blood samples from 411 participants with dyslipidemia and/or type 2 diabetes. Results The precision and accuracy of adLDL-Ch were verified by BQ-RMP. The mean percentage bias [bias (%)] for LDL-C was 1.2%, and the correlation was y = 0.990x + 3.361 (r = 0.990). These results met the acceptable range of accuracy prescribed by the National Cholesterol Education Program. Additionally, adLDL-Ch levels were correlated with LDL-C levels measured by the 2 homogeneous assays (r > 0.967) and the calculation methods (r > 0.939), in serum samples from patients with hypertriglyceridemia. Conclusions AEX-HPLC is a reliable method for measuring LDL-C levels for CVD risk in daily clinical laboratory analyses.

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Assessment of Digital PCR as a Primary Reference Measurement Procedure to Support Advances in Precision Medicine

Clinical Chemistry ◽

10.1373/clinchem.2017.285478 ◽

2018 ◽

Vol 64 (9) ◽

pp. 1296-1307 ◽

Cited By ~ 18

Author(s):

Alexandra S Whale ◽

Gerwyn M Jones ◽

Jernej Pavšič ◽

Tanja Dreo ◽

Nicholas Redshaw ◽

...

Keyword(s):

Precision Medicine ◽

Copy Number ◽

Digital Pcr ◽

Measurement Procedure ◽

Patient Treatment ◽

Molecular Diagnostic ◽

Reference Measurement ◽

Reference Measurement Procedure ◽

Wide Range ◽

Primary Reference

Abstract BACKGROUND Genetic testing of tumor tissue and circulating cell-free DNA for somatic variants guides patient treatment of many cancers. Such measurements will be fundamental in the future support of precision medicine. However, there are currently no primary reference measurement procedures available for nucleic acid quantification that would support translation of tests for circulating tumor DNA into routine use. METHODS We assessed the accuracy of digital PCR (dPCR) for copy number quantification of a frequently occurring single-nucleotide variant in colorectal cancer (KRAS c.35G>A, p.Gly12Asp, from hereon termed G12D) by evaluating potential sources of uncertainty that influence dPCR measurement. RESULTS Concentration values for samples of KRAS G12D and wild-type plasmid templates varied by <1.2-fold when measured using 5 different assays with varying detection chemistry (hydrolysis, scorpion probes, and intercalating dyes) and <1.3-fold with 4 commercial dPCR platforms. Measurement trueness of a selected dPCR assay and platform was validated by comparison with an orthogonal method (inductively coupled plasma mass spectrometry). The candidate dPCR reference measurement procedure showed linear quantification over a wide range of copies per reaction and high repeatability and interlaboratory reproducibility (CV, 2%–8% and 5%–10%, respectively). CONCLUSIONS This work validates dPCR as an SI-traceable reference measurement procedure based on enumeration and demonstrates how it can be applied for assignment of copy number concentration and fractional abundance values to DNA reference materials in an aqueous solution. High-accuracy measurements using dPCR will support the implementation and traceable standardization of molecular diagnostic procedures needed for advancements in precision medicine.

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