Comparison of Diabetes Diagnostic Categories in the U.S. Population According to 1997 American Diabetes Association and 1980–1985 World Health Organization Diagnostic Criteria

OBJECTIVE To compare the 1997 American Diabetes Association (ADA) and the 1980–1985 World Health Organization (WHO) diagnostic criteria in categorization of the diabetes diagnostic status of adults in the U.S.

RESEARCH DESIGN AND METHODS Analyses are based on a probability sample of the U.S. population age 40–74 years in the 1988–1994 Third National Health and Nutrition Examination Survey (NHANES III). People with diabetes diagnosed before the survey were identified by questionnaire. For 2,844 people without diagnosed diabetes, fasting plasma glucose was obtained after an overnight 9 to < 24-h fast, HbA_1c was measured, and a 2-h oral glucose tolerance test was administered.

RESULTS Prevalence of diagnosed diabetes in this age-group is 7.9%. Prevalence of undiagnosed diabetes is 4.4% by ADA criteria and 6.4% by WHO criteria. The net change of −2.0% occurs because 1.0% are classified as having undiagnosed diabetes by ADA criteria but have impaired or normal glucose tolerance by WHO criteria, and 3.0% are classified as having impaired fasting glucose or normal fasting glucose by ADA criteria but have undiagnosed diabetes by WHO criteria. Prevalence of impaired fasting glucose is 10.1% (ADA), compared with 15.6% for impaired glucose tolerance (WHO). For those with undiagnosed diabetes by ADA criteria, 62.1% are above the normal range for HbA_1c compared with 47.1% by WHO criteria. Mean HbA_1c is 7.07% for undiagnosed diabetes by ADA criteria and 6.58% by WHO criteria.

CONCLUSIONS The number of people with undiagnosed diabetes by ADA criteria is lower than that by WHO criteria. However, those individuals classified by ADA criteria are more hyperglycemic, with higher HbA_1c values and a greater proportion of values above the normal range. This fact, together with the simplicity of obtaining a fasting plasma glucose value, may result in the detection of a greater proportion of people with undiagnosed diabetes in clinical practice using the new ADA diagnostic criteria.