Lack of agreement between the World Health Organization category of impaired glucose tolerance and the American Diabetes Association category of impaired fasting glucose

OBJECTIVE - To study the concordance between the 1997 American Diabetes Association (ADA) impaired fasting glucose (IFG) category with the World Health Organization (WHO) impaired glucose tolerance (IGT) status in a population with a high prevalence of diabetes. RESEARCH DESIGN AND METHODS - We analyzed the oral glucose tolerance tests (OGTTs) carried out at the Institute Nacional de la Nutricion Salvador Zubiran (INNSZ) central laboratory from June to December 1997. We included patients with fasting plasma glucose (FPG) between 60 and 160 mg/dl. The results from the glucose tolerance test were selected as the gold standard. RESULTS - Among the 1,802 glucose tolerance test results available for analysis, 1,706 fulfilled the requirements to be included. Diabetes and IGT were remarkably more frequently diagnosed when the WHO criteria were applied. The new ADA criteria failed to diagnose 69% of WHO diabetic patients and the vast majority of WHO glucose-intolerant subjects. Using the new criteria, 82% were considered normal. Of the IFG subjects, 39% were classified as diabetic and 23% were normal according to the 2-h postchallenge glucose values. Only 37% of the IFG patients were, in fact, glucose intolerant according to the WHO criteria. CONCLUSIONS - Our results clearly show that the 1997 ADA criteria are less sensitive for diagnosing diabetes than OGTT-based WHO criteria. Even more important, there is poor agreement between the WHO category of IGT and the ADA category of IFG.