New diagnostic criteria for diabetes mellitus announced by ADA in 1997 and WHO in 1998 recommend lowering of the fasting plasma glucose to 7.0 mmol/l and introduce new category: impaired fasting glucose. In contrast to ADA, WHO recommends to maintain oral glucose tolerance test in clinical practice. In this study, based on oral glucose tolerance test results and WHO 1998 criteria we estimated diagnostic value of fasting glucose in diagnosing diabetes. The aim of the study was also to compare prevalence of diabetes and other categories of glucose intolerance according to ADA 1997, WHO 1985 and WHO 1998 criteria.
Methods: Oral glucose tolerance test (OGTT) was performed in 1528 patients (785 men, 743 women). According to ADA 1997, WHO 1985 and WHO 1998 criteria the patients were divided into groups depending on glucose tolerance abnormalities.
Results: Prevalence of diabetes according to ADA 1997 and WHO 1985 criteria was almost the same, being 10.47% and 10.34%, respectively, and according to WHO 1998 criteria it was 13.15%. In 20.4% of all the patients with diabetes according to WHO 1998 criteria, the diagnosis was made on the basis of 2-h post load glucose, in case of WHO 1985 criteria the percentage was 39.9%. 13.04% of patients with IFG according to ADA had diabetes and 34.06% had IGT according to WHO 1998 criteria. The highest overall percentage agreement (97.19%) was found between WHO 1998 and WHO 1985 classifications with the hypothesis that unclassified group according to WHO 1985 corresponds to IFG group according to WHO 1998.
Conclusions: Despite lower diagnostic value of 2-hour post-load glycaemia in diagnosing diabetes according to WHO 1998 criteria compared to WHO 1985 criteria, OGTT remains irreplaceable diagnostic tool, especially in high risk populations. In patients with IFG according to ADA OGTT causes significant improvement in detecting diabetes.