COMPARISONS OF STUDIES ON DIABETIC COMPLICATIONS HAMPERED BY DIFFERENCES IN GHB MEASUREMENTS

OBJECTIVE - To compare glycated hemoglobin (GHb) values of the relatio nship between glycemic control and complications of diabetes from labo ratories involved in long-term studies (Steno, Oslo, Stockholm, Diabet es Control and Complications Trial, and Linkoping). RESEARCH DESIGN AN D METHODS - Blood samples were collected from 25 subjects selected to represent the clinically relevant measurement range. Fresh whole-blood samples were distributed and analyzed within 4 days of sample collect ion. Pretreatment of samples and analyses of GHb were performed accord ing to the routine method of each study's central or reference laborat ory. Results from each laboratory were compared with the group mean, i .e., the mean of all results for each sample. RESULTS - Regression ana lyses with the group mean values as independent variables and results from each laboratory as dependent variables showed that Oslo's results had a slope significantly different from the group mean. Laboratories used by the DCCT, Oslo, and Steno studies gave, on average, 0.4, 0.4, and 0.7% higher HbA(1c) readings than the group mean, respectively, w hile HbA(1c) results from Linkoping and Stockholm were, on average, 0. 6 and 1.0% lower, respectively. CONCLUSIONS - There were large differe nces in GHb values among laboratories participating in studies of diab etic complications. The present data offer a guide to the comparison o f results from the studies and underscores the need for standardizatio n of GHb measurements.