STANDARDIZATION OF GLYCOHEMOGLOBIN RESULTS AND REFERENCE VALUES IN WHOLE-BLOOD STUDIED IN 103 LABORATORIES USING 20 METHODS

We investigated the effect of calibration with lyophilized calibrators on whole-blood glycohemoglobin (glyHb) results. One hundred three lab oratories, using 20 different methods, determined glyHb in two lyophil ized calibrators and two whole-blood samples. For whole-blood samples with low (5%) and high (9%) glyHb percentages, respectively, calibrati on decreased overall interlaboratory variation (CV) from 16% to 9% and from 11% to 6% and decreased intermethod variation from 14% to 6% and from 12% to 5%. Forty-seven laboratories, using 14 different methods, determined mean glyHb percentages in self-selected groups of 10 nondi abetic volunteers each. With calibration their overall mean (2SD) was 5.0% (0.5%), very close to the 5.0% (0.3%) derived from the reference method used in the Diabetes Control and Complications Trial. In both e xperiments the Abbott IMx and Vision showed deviating results. We conc lude that, irrespective of the analytical method used, calibration ena bles standardization of glyHb results, reference values, and interpret ation criteria.