External quality assessment of hemoglobin A2 measurement : data from an Italian pilot study with fresh whole blood samples and commercial HPLC systems

BACKGROUND: To evaluate the extent of interlaboratory variation and accuracy in hemoglobin A(2) (HbA(2)) assays, a pilot study of external quality assessment was organized among 48 Italian laboratories routinely measuring HbA(2). As part of the study, a survey was also performed by sending a questionnaire concerning some important analytical aspects related to the determination of HbA(2). METHODS: The trial specimens consisted of three whole blood samples (A, B and C) with normal, pathological and borderline HbA(2) content, respectively. All laboratories used HPLC analyzers from the same manufacturer (Bio-Rad Laboratories). RESULTS: Normal and pathological samples were clearly differentiated by all laboratories, while data for the borderline sample partially overlapped those for the other samples. The overall interlaboratory coefficient of variation was 8.0%, 6.0% and 7.9% for samples with low, high and intermediate HbA(2) levels, respectively. To assign HbA(2) target values to the samples, the median of the laboratory group was used. The accuracy of HbA(2) results was evaluated on the basis of allowable total error. The proportion of laboratories reporting unacceptable results was 31.9% (15 out of 47) for sample A, 17.0% (8 out of 47) for sample B, and 31.9% (15 out of 47) for sample C. No abnormalities in the chromatographic separation pattern were reported by any of the laboratories. CONCLUSIONS: We conclude that quality in the measurement of HbA(2) should be improved.