Multicenter evaluation of the commutability of a potential reference material for harmonization of enzyme activities
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Volkher Scharnhorst
Abstract
Standardization of laboratory results allows for the use of common reference intervals and can be achieved via calibration of field methods with secondary reference materials. These harmonization materials should be commutable, i.e., they produce identical numerical results independent of assay principle or platform. This study assessed the commutability of a cryolyoprotectant-containing harmonization material, obtained from the Dutch Foundation for Quality Assessment in Clinical Laboratories, that is intended to harmonize measurements of enzyme activities within the Dutch project “Calibration 2000”. The catalytic concentrations of alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, γ-glutamyltransferase and creatine kinase were analyzed in pooled patient sera and in the reference material in 14 laboratories. On liquid chemistry analyzers the harmonization material behaves like patient material. The enzyme activities measured in it fall on the regression lines calculated from activities measured in serum samples. For dry chemistry analyzers the activities of all enzymes measured in the harmonizator differ from the serum-based regression line. We show that this is due to the sucrose-containing cryolyoprotectant in the harmonization material. For each enzyme, correction factors were calculated that compensated for the bias and proved to be constant between reagent lots. Depending on the enzyme activity measured, application of these factors leads to 2- to 10-fold reduction of between-laboratory percentage coefficient of variation. Thus, additives to (potential) reference materials may alter their matrix in a way that interferes with analysis on certain test systems. The bias caused may be quantifiable and correctable. Establishment of correction factors leads to analytical uncertainties and costs. Therefore, matrix-based materials without additives should be selected as reference materials.
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©2004 by Walter de Gruyter Berlin New York
Articles in the same Issue
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- Artificial neural network-based algorithm for the evaluation of serum protein capillary electrophoresis
- State-of-the-art systematic error for therapeutic drug monitoring
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- Erratum
Articles in the same Issue
- Contents
- Author Index
- Subject Index
- Hematopoietic cytokines as tumor markers
- The apoB/apoA-I ratio is better than the cholesterol ratios to estimate the balance between plasma proatherogenic and antiatherogenic lipoproteins and to predict coronary risk
- Rapid combined genotyping of factor V, prothrombin and methylenetetrahydrofolate reductase single nucleotide polymorphisms using minor groove binding DNA oligonucleotides (MGB probes) and real-time polymerase chain reaction
- Methylenetetrahydrofolate reductase gene A222V polymorphism and risk of ischemic stroke
- Determination of asymmetric dimethylarginine (ADMA) using a novel ELISA assay
- The assessment of bone metabolism in female elite endurance athletes by biochemical bone markers
- Declines in serum free and bound choline concentrations in humans after three different types of major surgery
- Analysis of inflammatory response in human plasma samples by an automated multicapillary electrophoresis system
- Multicenter evaluation of the commutability of a potential reference material for harmonization of enzyme activities
- HDL and clinical and biochemical correlates in Italian non-smoker women
- Hyperhomocysteinaemia is associated with uveitis but not with deep venous thrombosis in Behçet's disease
- Production of gender-specific morning salivary cortisol reference intervals using internationally accepted procedures
- Concentrations of N-terminal pro-brain natriuretic peptide and troponin T in plasma of 75-year-old apparently healthy persons
- External Quality Assessment for biochemical markers of myocardial damage: an Italian experience
- Further evaluation of the immunonephelometric assay of soluble transferrin receptor and assessment of pediatric values in southern Italy
- Exercise raises serum heat-shock protein 70 (Hsp70) levels
- Hepatitis C-associated complement cold activation
- The relationship between cryoglobulins and HCV-RNA in the serum of patients infected with different HCV genotypes
- Artificial neural network-based algorithm for the evaluation of serum protein capillary electrophoresis
- State-of-the-art systematic error for therapeutic drug monitoring
- Peculiarities and problems with the EXCEL® F-test
- Questionable results – should EQA results be accepted as submitted or should ‘obvious mistakes’ be corrected?. Reply to Wood WG. Questionable results – who directs the EQAS organisers? CCLM 2004;42(9):1073
- Erratum
