COMPARISON BETWEEN A RAPID GLYCOHEMOGLOBIN (HB(A1C)) IMMUNOASSAY AND OTHER INDEXES OF GLYCEMIC CONTROL

The aims of the study were to compare glycohaemoglobin (Hb(A1c)) value s measured by DCA (a benchtop analyzer primarily designed for within-c linic rapid Hb(A1c) determination) to a reference Hb(A1c) method and h ome blood glucose monitoring, and to explore the possibility of an uni form expression of data. A total of 103 blood samples and the correspo nding mean capillary glucose values (4.4+/-1.2 tests/day) of the prece ding 2 months were collected from 34 insulin-dependent diabetic adults . We measured the correlations and agreements using the residual plots method and regression equations between Hb(A1c) measured by DCA and h igh-pressure liquid chromatography (HPLC), and between DCA and capilla ry glucose values. A highly significant correlation (r(2)=0.85, P<0.00 1) and an acceptable agreement (97% of values within 2 SD of the mean difference of 0.9%+/-0.4%) was found between DCA and HPLC values. The regression equation calculated on the first half of the cases was: DCA (%)=0.72 HPLC (%)+1.38. Of DCA values expressed in HPLC terms using t his equation 87% fell within a clinically acceptable confidence interv al when compared with measured HPLC data. A significant correlation (r (2)=0.40, P<0.01) was found between DCA and capillary glucose values, and the regression equation was: DCA (%)=0.34 capillary glucose (mM)+4 .44. Of glycaemic levels calculated from DCA values using this formula 82% fell within a clinically acceptable error range when compared wit h measured glycaemic values. We conclude that the three methods of ass essment of diabetes control an well correlated and that it is possible , with a degree of precision acceptable for the clinical setting, to e xpress all data in uniform units, e.g. mM of capillary glucose or perc entage of HPLC-Hb(A1c), though a simple correspondence table based on our transfer equations may be clinically sufficient and more handy.