Predicting Future Cardiovascular Disease
Do we need the oral glucose tolerance test?
MICHAEL P. STERN, MD
PEDRAM FATEHI, MPH
KEN WILLIAMS, MS
STEVEN M. HAFFNER, MD
OBJECTIVE — Our objective was to compare the performance of oral glucose tolerance tests
(OGTTs) and multivariate models incorporating commonly available clinical variables in their
ability to predict future cardiovascular disease (CVD).
RESEARCH DESIGN AND METHODS — We randomly selected 2,662 Mexican-
Americans and 1,595 non-Hispanic whites, 25–64 years of age, who were free of both CVD and
known diabetes at baseline from several San Antonio census tracts. Medical history, cigarette
smoking history, BMI, blood pressure, fasting and 2-h plasma glucose and serum insulin levels,
triglyceride level, and fasting serum total, LDL, and HDL cholesterol levels were obtained at
baseline. CVD developed in 88 Mexican-Americans and 71 non-Hispanic whites after 7–8 years
of follow-up. Stepwise multiple logistic regression models were developed to predict incident
CVD. The areas under receiver operator characteristic (ROC) curves were used to assess the
predictive power of these models.
RESULTS — The area under the 2-h glucose ROC curve was modestly but not significantly
greater than under the fasting glucose curve, but both were relatively weak predictors of CVD.
The areas under the ROC curves for the multivariate models incorporating readily available
clinical variables other than 2-h glucose were substantially and significantly greater than under
the glucose ROC curves. Addition of 2-h glucose to these models did not improve their predict-
CONCLUSIONS — Better identification of individuals at high risk for CVD can be achieved
with simple predicting models than with OGTTs, and the addition of the latter adds little if
anything to the predictive power of the model.
Diabetes Care 25:1851–1856, 2002
individuals with impaired glucose toler-
ance (IGT), because such individuals are
at increased risk for diabetes. We have
previously shown that individuals at high
risk for diabetes can be more efficiently
identified using multivariate models that
do not require OGTT (1). A second rea-
principal reason that is typically
given for screening large segments
of the population with 2-h oral glu-
son that is typically given for screening
the population for IGT is that individuals
with this condition are also at increased
risk for cardiovascular disease (CVD)
(2,3). In this study, we examine the pos-
tion of individuals at high risk for CVD
can be achieved using readily available
clinical measurements that, again, do not
curves in which the sensitivity of a test is
plotted against the corresponding false-
positive rate. In the present context, sen-
sitivity refers to the percentage of
individuals whose initial values were
above a given cutpoint among those who
later developed CVD and false-positive
rate refers to the percentage of these indi-
mained free of CVD. The area under the
ROC curve measures how well a contin-
uous variable predicts the outcome of in-
only a relatively slow accumulation of
false positives, the area under the ROC
curve will be large; conversely, if the sen-
sitivity increases slowly as the threshold
for diagnosis is relaxed with a rapid accu-
mulation of false positives, the area under
the ROC curve will be correspondingly
smaller. The differences in areas may be
tested to determine whether they are sta-
tistically significant. We have used this
approach to compare the fasting glucose
value and the value 2 h after an oral glu-
cose load with various multivariate mod-
els for predicting future CVD.
RESEARCH DESIGN AND
METHODS — The data presented in
this report were collected as part of the
San Antonio Heart Study, the methods of
which have been previously described
(4–6). Briefly, households were ran-
borhoods: low, middle, and high income.
Individuals residing in these households
were eligible for the study if they were
between the ages of 25 and 64 years and,
if women, were not pregnant. There were
no other exclusions, except that only
Mexican-Americans were recruited from
ing a negligible number of non–Mexican-
American individuals residing in these
neighborhoods. Stratified random sam-
pling was used in the middle- and high-
income neighborhoods to recruit an
approximately equal number of Mexican-
● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●
From the Division of Clinical Epidemiology, Department of Medicine, University of Texas Health Science
Center at San Antonio, San Antonio, Texas.
Antonio, TX 78229-3900. E-mail: firstname.lastname@example.org.
Received for publication 22 January 2002 and accepted in revised form 29 June 2002.
Abbreviations: CVD, cardiovascular disease; IGT, impaired glucose tolerance; OGTT, oral glucose tol-
erance test; ROC, receiver operator characteristic.
A table elsewhere in this issue shows conventional and Syste `me International (SI) units and conversion
factors for many substances.
See Point-Counterpoint, p. 1879.
E p i d e m i o l o g y / H e a l t h S e r v i c e s / P s y c h o s o c i a l R e s e a r c h
O R I G I N A LA R T I C L E
DIABETES CARE, VOLUME 25, NUMBER 10, OCTOBER 2002
17. Burke JP, Haffner SM, Gaskill SP, Wil-
diabetes to nondiabetic status: influence
of the 1997 American Diabetes Associa-
tion criteria. Diabetes Care 21:1266–1270,
18. Population projections of the United
States by age, sex, race, Hispanic origin,
and nativity [article online], 1999–2000.
Available from http://www.census.gov/
dl-a.txt. Accessed February 2001
19. Stolk RP, Grobbee DE, Orchard TJ: Why
use the oral glucose tolerance test? Diabe-
tes Care 18:1045–1049, 1995
Optimal prediction of cardiovascular disease
DIABETES CARE, VOLUME 25, NUMBER 10, OCTOBER 2002