Diabetes Care, Vol 17, Issue 5 436-439, Copyright © 1994 by American Diabetes Association
Fasting plasma glucose in screening for NIDDM in the U.S. and Israel
M Modan and MI Harris
Department of Clinical Epidemiology, Chaim Sheba Medical Center, Tel Hashomer, Israel.
OBJECTIVE--To demonstrate the inadequacy of fasting plasma glucose for
screening for NIDDM, even among groups at high risk for diabetes. RESEARCH
DESIGN AND METHODS--Representative samples of adults 40-69 years of age in
the U.S. (n = 2,035) and Israel (n = 2,316) were selected. Fasting plasma
glucose (FPG) was measured and a 2-h oral glucose tolerance test (OGTT) was
administered. Subjects with undiagnosed NIDDM were identified using
internationally accepted diagnostic criteria (FPG > or = 7.8 mM or 2-h
plasma glucose > or = 11.1 mM). RESULTS--Only 31-38% of subjects with
undiagnosed NIDDM had fasting hyperglycemia (> or = 7.8 mM), and 36% in
the U.S. and 19% in Israel had normoglycemia (< 6.1 mM). Postchallenge
glucose, diagnostic of diabetes, was associated with all fasting values,
including values < 5.0 mM. Based on sensitivity, specificity, and
positive predictive value, no FPG level provided a satisfactory cutoff
point to use in screening for undiagnosed NIDDM. Sensitivity at each FPG
cutoff point varied little among groups classified by age, sex, race, blood
pressure status, or body mass index (BMI) levels > 23, but sensitivity
was lower among those with BMI levels < 23. CONCLUSIONS--In the clinical
setting, FPG is commonly used in screening for NIDDM. However, fasting
values < or = 7.8 mM are highly insensitive for detecting NIDDM. Lower
FPG cutoff points tha achieve acceptable sensitivity are accompanied by
inadequately low specificity, require a high percentage of patients to be
retested, and result in a low yield of diabetes among those screened.
Clinicians and researchers who seek detection of undiagnosed NIDDM should
use the OGTT, because FPG lacks adequate sensitivity and specificity for
this purpose.