Application of sigma metrics for the assessment of quality assurance using the MQ-2000 PT HbA1c analyzer

Glycosylated hemoglobin (HbA1c) concentrations measured in clinical chemistry laboratories show large differences between their interlaboratory reported values. Laboratory measurements of quality performance should be based on quantitative data. The sigma metrics model provides an objective method for the assessment of current HbA1c assays and is useful in quality management planning. The aim of our study was to evaluate the analytical performance of the MQ-2000 PT HbA1c analyzer test results in the context of our operating conditions on the sigma scale.

The coefficient of variation was determined from the calculated mean and standard deviation evaluated from internal quality control (QC) (N=168 days) (Shanghai Huachen Biological Reagent Co. Ltd, China) data, and records of external quality data (KBUDEK, İstanbul, Turkey) measured in the period from May to November 2013 were used to determine the bias. The resulting data and total allowable error rate (TEA=10%) from the Clinical Laboratory Improvement Amendments of 1988 (CLIA'88) were used to calculate the sigma level.

The calculated coefficient of variations (CVs) at the two levels, normal (QC1=36.6±2.38 mmol/mol) and pathological (QC2=84.7±2.68 mmol/mol), were 6.5% and 3.1%, respectively. The average bias between the external QC and MQ-2000 PT during the study period was 4.3%. The calculated average sigma value was 1.19.

The MQ-2000 PT HbA1c is a new analyser in the market; there is need for improvement and the method should be controlled with greater attention to ensure quality.