WITH REGARD TO GLYCOHEMOGLOBIN MEASUREMENT - ARE WE SURE THAT HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY CURRENTLY WORKS IN THE CLINICAL ROUTINE

The clinical usefulness of glycated hemoglobin (HbA(1c)) depends cruci ally on the accuracy and precision of its assay. When we compared an i mmunological bench-top analyzer (DCA 2000, Bayer Diagnostici, Milan) t o the high-performance liquid chromatography (HPLC) reference method u sed in a routine hospital laboratory (Diamat and Fast Diamat, Bio-Rad Lab., Milan) by assaying multiple control sera, we found so many sourc es of systematic analytical errors in the routine use of HPLC as to co mpromise between-assay precision. DCA 2000 showed intra-and interassay coefficients of variation (CV) of 1.1% and 2.3% with the normal stand ard serum, 1.0% and 4.2% with the pathological one; Diamat yielded CVs of 1.3% and 7.0%, 1.3% and 5.7%, respectively. Although the measureme nt of 161 blood samples showed that Diamat usually overestimated HbA(1 c) (paired t-test, P<0.001), a great variability of Diamat performance became evident when the relationship Diamat vs DCA was evaluated day by day over 17 days of observation (analysis of variance, ANOVA, P<0.0 01). Intra-and interassay CVs of Fast Diamat initially (new instrument still on approval) were 0.6% and 2.5% (normal standard serum), 0.3% a nd 1.9% thigh standard serum), yet after 6 months of routine laborator y use, they became 3.1% and 3.2%, 1% and 12.3%, respectively. Main sou rces of error were: inaccurate autodilution, unsuitable parameter sett ings, disregard of the maintenance schedule. We conclude that the tend ency to overlook major critical aspects in the routine use of HPLC is detrimental to the quality of HbA(1c) determination and implies the lo ss of HbA(1c) value in clinical practice. Both carefully supervising l aboratory quality and checking the likelihood of the analytical result with the clinical setting appear even more important.