Glycated hemoglobin measurement: Intermethod comparison

Clinical interpretation of changes in serial measurements of patients' HbA( 1c) ought to be based on the knowledge of pre-analytical, analytical and in tra-individual sources of variation that affect the results. The detectable change in HbA(1c) percentage depends on total analytical error. Since we h ave previously evidenced major problems in the routine use of HPLC, we comp ared a highly automated glycohemoglobin assay with the reference RPLC to so lve the problem. The within- and between-run coefficients of variations ran ged from 0.86 to 0.93%, and 2.51 to 2.12%, respectively, for the HPLC, and from 1.07 to 0.95, and 1.61 to 0.99% for the immunoturbidimetric assay. Aft er HbA(1c)- assay calibration, the quality-control survey report of duplica te determinations performed on 20 consecutive days by both the HPLC and the immunologic method provided the expected mean values of control materials. The assay of 106 blood samples showed a minor yet significant bias of the immunoturbidimetric assay toward lower HbA(1c) values (p 0.0001), as previo usly observed, although the two determination series resulted significantly correlated (r=0.96,p=0.0001). We conclude that the immunoturbidimetric ass ay is surely accurate, precise, and reproducible, and represents a valid al ternative to the reference HPLC assay. (C) 2001, Editrice Kurtis.