Diabetes in Oman: Comparison of 1997 American Diabetes Association Classification of Diabetes Mellitus with 1985 WHO Classification

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Diabetes mellitus (DM) is a major public health problem in Oman. We evaluated the impact of the revised diagnostic criteria for DM adopted by the American Diabetes Association (ADA) on the prevalence of diabetes and impaired glucose tolerance (IGT), and on the classification of individuals among the Omani population. We used the dataset of the National Diabetes Survey, conducted in 1991 and involving 4682 subjects who did not have any missing data on fasting and 2-hour glucose. The subjects comprised 2002 males and 2680 females aged 20 years or above. Data were analyzed using the ADA criteria (diabetes as fasting plasma glucose [FPG] > or =7 mmol/L, impaired fasting glucose [IFG] as FPG > or =6.1 mmol/L and <7 mmol/L), and compared these with the World Health Organization (WHO) criteria (diabetes as FPG > or =7.8 mmol/L and/or 2-hour post-glucose load > or =11.1 mmol/L, IGT as FPG <7.8 mmol/L, and 2-hour post-load 7.8-11.1 mmol/L). Applying the ADA criteria on the Omani population resulted in an overall reduction of diabetes prevalence by 2.2% (95% confidence interval [CI] 1.6% to 2.8%), and a 4.8% reduction of IGT (95% CI 3.8% to 5.8%). Over 29% of diabetics classified by the WHO criteria were reclassified as being normal or having IFG by the ADA criteria. Around 3.6% of those who were normoglycemic by the WHO criteria were classified as having diabetes or IFG by the ADA criteria. In all but one region of Oman, the prevalence of diabetes and IFG using the ADA criteria was lower compared to the prevalence using the WHO criteria. Gender, age and body mass index did not seem to pose an increased risk to the probability of being diagnosed by one criteria or the other or both together. The adoption of the ADA criteria in Oman will significantly reduce the prevalence of diabetes and IGT. In addition, the glycemic status of a substantial number of individuals will be changed from normal to either being diabetic or having IGT.