Application of the new ADA criteria for the diagnosis of diabetes to population studies in sub-Saharan Africa

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Abstract
Aims To examine the implications for epidemiological studies of the American Diabetes Association (ADA) recommendation that the fasting blood glucose at a lowered level becomes the main diagnostic test for diabetes on cross-sectional-based data from sub-Saharan Africa. Methods Data from 11 surveys conducted in rural, peri-urban and urban Cameroon (n = 1804), South Africa (n = 3799) and Tanzania (n = 10013) which measured fasting (ADA criteria) and 2-h blood glucose concentrations during a standard 75 g OGTT (old WHO criteria) were analysed. Results The prevalence of diabetes was higher in eight of the 11 surveys when applying the new ADA compared to the old WHO criteria. With the exception of one population (Mara, Tanzania) the absolute difference in prevalence between the two classifications tended to be small (< 2%). There was considerable variation in the categorization of individuals using the ADA and old WHO criteria. The level of agreement between the two ranged from fair to good (Kappa statistic 0.17–0.86). The prevalence of impaired fasting glycaemia (IFG) was lower than that of impaired glucose tolerance (IGT) in 10 of the surveys and the agreement between the two was fair, 0.26 in all the surveys. Conclusions Although the use of the new ADA fasting criteria for prevalence surveys is an attractive and practical option, particularly in Africa, further information is required on the characteristics and prognosis of individuals classified as IFG or diabetic by the fasting criteria, prior to wide adoption of the ADA criteria. Ideally measurement of both fasting and two low glucose concentrations should remain the standard for epidemiological studies.