Diabetes, Vol 37, Issue 1 60-64, Copyright © 1988 by American Diabetes Association
Relationship of glycosylated hemoglobin to oral glucose tolerance. Implications for diabetes screening
RR Little, JD England, HM Wiedmeyer, EM McKenzie, DJ Pettitt, WC Knowler and DE Goldstein
Department of Pathology, University of Missouri School of Medicine, Columbia 65212.
The oral glucose tolerance test (OGTT) for diagnosis of diabetes is
inconvenient and requires a great deal of patient cooperation. Glycosylated
hemoglobin (GHb), an index of long-term glycemic control, could offer
several practical advantages over the OGTT for diabetes screening. We
evaluated GHb as a screen for diabetes in 381 adults from a population with
a high prevalence of non-insulin-dependent diabetes (Pima Indians). All
individuals underwent a standard OGTT (75 g) and were separated into one of
three groups: normal (N), impaired glucose tolerance (IGT), or diabetes
mellitus (D) based on World Health Organization criteria. HbA1c, a GHb, was
measured by highly precise high-performance liquid chromatography
(interassay C.V. less than 4%). The normal range for HbA1c was 4.07-6.03%
based on the 95% confidence interval for a nondiabetic, mostly Caucasian
population. Compared with OGTT, HbA1c was highly specific (91%); an
elevated HbA1c usually indicated D or IGT (sensitivity = 85 and 30%,
respectively). A normal HbA1c did not, however, exclude a diagnosis of D or
IGT. Based on previous epidemiological studies relating plasma glucose to
chronic diabetic complications, GHb as measured in this study would
properly identify the vast majority of subjects at risk. Long-term studies
are necessary to determine the actual risk of complications in individuals
with persistently normal HbA1c and D or IGT (based on OGTT).