Hemoglobin A1c measurements over nearly two decades: sustaining comparable values throughout the Diabetes Control and Complications Trial and the Epidemiology of Diabetes Interventions and Complications study.
BACKGROUND
Clinical trials require assays that provide consistent results during the course of a study. The hemoglobin A1c (HbA1c) assay, a measure of chronic glycemia, is critical to the study of diabetes control and complications.


METHODS
The Diabetes Control and Complications Trial (DCCT) and its follow-up study, the Epidemiology of Diabetes Interventions and Complications (EDIC), required 20 years of consistent HbA1c results, measured by three different ion-exchange HPLC procedures. To maintain and document consistent HbA1c results measured in the DCCT and EDIC Central Biochemistry Laboratory, a backup laboratory used frozen hemolysates as long-term calibrators and a HPLC method with a single lot of Bio-Rex 70 resin.


RESULTS
Over 20 years, long-term quality-control values have remained constant. Four studies of nondiabetic ranges produced nearly identical values [mean (SD), 5.1 (0.5)%, 4.9 (0.3)%, 5.0 (0.4)%, and 5.0 (0.3)%].


CONCLUSIONS
The overall consistency of the HbA1c assays during the 20-year course of the DCCT and EDIC has been critical in establishing the benefits of intensive therapy and in understanding the relationship between long-term glycemia and the development and progression of the complications of diabetes.
Steffes
Michael
M
Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN 55454, USA. steff001@umn.edu
Cleary
Patricia
P
Goldstein
David
D
Little
Randie
R
Wiedmeyer
Hsiao-Mei
HM
Rohlfing
Curt
C
England
Jack
J
Bucksa
Jean
J
Nowicki
Maren
M
D002851:Chromatography, High Pressure Liquid / Q000592:standards; D019411:Clinical Laboratory Techniques / Q000592:standards*; D002986:Clinical Trials as Topic; D048909:Diabetes Complications / Q000175:diagnosis / Q000517:prevention & control; D003920:Diabetes Mellitus / Q000175:diagnosis* / Q000453:epidemiology / Q000517:prevention & control; D006442:Glycated Hemoglobin / Q000032:analysis* / Q000592:standards; D006801:Humans; D007753:Laboratories / Q000592:standards; D011786:Quality Control; D012015:Reference Standards; D013995:Time
D006442:Glycated Hemoglobin