Value of risk stratification to increase the predictive validity of HbA1c in screening for undiagnosed diabetes in the US population.
BACKGROUND
Opportunistic screening using hemoglobin A1c (HbA1c) may improve detection of undiagnosed diabetes but remains controversial.


OBJECTIVE
To evaluate the predictive validity of HbA1c as a screening test for undiagnosed diabetes in a risk-stratified sample of the US population.


METHODS
Weighted cross-sectional analysis of diabetes risk factors, HbA1c, and fasting plasma glucose (FPG) in National Health and Nutrition Examination Survey (NHANES), 1999-2004.


METHODS
Six thousand seven hundred and twenty-three NHANES participants from morning examination session, aged > or = 18 years and without prior physician-diagnosed diabetes.


METHODS
HbA1c and undiagnosed diabetes defined by FPG > or = 7.0 mmol/l (126 mg/dl).


RESULTS
The estimated prevalence of undiagnosed diabetes in the US population was 2.8% (5.5 million people). HbA1c had strong correlation with undiagnosed diabetes, with an area under the receiver-operating characteristic curve of 0.93. Independent predictors of undiagnosed diabetes were older age, male sex, black race, hypertension, elevated waist circumference, elevated triglycerides, and low high-density lipoprotein cholesterol. We derived a risk score for undiagnosed diabetes and stratified participants into low (0.44% prevalence), moderate (4.1% prevalence), and high (11.1% prevalence) risk subgroups. In moderate and high risk groups, a threshold HbA1c value > or = 6.1% identified patients requiring confirmatory FPG; HbA1c < or = 5.4% identified patients for whom diabetes could be reliably excluded. Intermediate HbA1c (5.5-6.0%) may exclude diabetes in moderate, but not high risk groups).


CONCLUSIONS
Risk stratification improves the predictive validity of HbA1c in screening for undiagnosed diabetes in the US population. Although opportunistic screening with HbA1c would improve detection of undiagnosed diabetes, cost-effectiveness studies are needed before implementation of specific screening strategies using HbA1c.
Ginde
Adit A
AA
Department of Emergency Medicine, University of Colorado Denver School of Medicine, Aurora, CO 80045, USA. adit.ginde@uchsc.edu
Cagliero
Enrico
E
Nathan
David M
DM
Camargo
Carlos A
CA
D000293:Adolescent; D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000032:analysis*; D003920:Diabetes Mellitus / Q000175:diagnosis* / Q000453:epidemiology; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis*; D006305:Health Status Indicators; D006801:Humans; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D009749:Nutrition Surveys; D011237:Predictive Value of Tests; D015995:Prevalence; D014481:United States / Q000453:epidemiology
D001786:Blood Glucose; D006442:Glycated Hemoglobin