HbA1c enzymatic assay evaluation at an academic laboratory

Abstract

Background: HbA1c is a well-known and widely accepted marker for monitoring glycaemic control in patients with Diabetes Mellitus. It has also been shown to predict long term microvascular complications associated with Diabetes Mellitus. As a result the International Expert Committee has endorsed HbA1c as a diagnostic marker for Diabetes Mellitus. There are several assays available for the measurement of HbA1c and the recommended assay performance is an intralaboratory coefficient of variation of <2%. The aim of the study was to evaluate the analytical performance of the HbA1c enzymatic assay on the Abbott Architect ci8200. Method: The precision, reportable range and bias were determined by following The Clinical and Laboratory Standards Institute (CLSI) EP05, EP06 and EP15 guidelines. Bias was determined by comparison between the Abbott Architect and the Biorad Variant II analyser. Results: The total impresicion for low and high controls was 1.06% and 1.8% respectively. The assay demonstrated excellent correlation with the Biorad Variant II analyser with a slope of 0.923, intercept of 0.569 and R2 of 0.978. The Bland-Altman mean difference was 0.044 between the Abbott Architect and Biorad Variant II analysers. At the diagnostic and monitoring cut-off, the bias was found to be 1.05% and 0.43% respectively. Conclusion: The new enzymatic HbA1c assay demonstrated good precision and had the advantage of rapid analysis thus prompt results reporting. The study also demonstrated acceptable agreement of the Abbott Architect and Bio-Rad Variant II methods across the measured range. Notably, the assay met analytical goals for the diagnosis and monitoring of Diabetes Mellitus using, as the total allowable error was 1.13% and 1.03% respectively, which was well below the 3% total allowable recommended error from biological data.