Oral Glucose Tolerance Test and Fasting Blood Glucose in the Diagnosis of Diabetes Mellitus

Objective: This study is planned to investigate the distribution of the oral glucose tolerance test requested patients from our hospital outpatient clinics, to observe the criteria that is used in the diagnosis of diabetes mellitus and to introduce the validity of these criteria. Oral glucose tolerance test was performed in 550 individuals in 2007 and those were included into the study which were selected from laboratory information system. Material and Methods: All the tests that were requested from the outpatient clinics before oral glucose tolerance test and the results after the glucose load were recorded. The patients that were classified according to fasting blood glucose and oral glucose tolerance test second hour blood glucose levels were grouped as normal, impaired fasting glucose, impaired glucose tolerance or diabetes mellitus. Blood glucose level was determined by hexokinase method in Olympus 2700 autoanalyzer, HbA1c level was determined by HPLC method in PDQA1c analyzer. Results: It was determined that oral glucose tolerance test was requested from individuals who had a fasting blood glucose of 108.3 +/- 18.7 mg/dL, and according to second hour blood glucose level, 61 people were classified as diabetes mellitus, 143 people had an impaired glucose tolerance, and 346 people were normal. According to fasting blood glucose, number of the normoglycemic patients decreased to 180, and the number of the diabetic patients decreased to 58. Sensitivity of fasting blood glucose for diabetes mellitus was found as 32.8%. Conclusion: Diagnosis ratio for new diabetes mellitus cases in our hospital outpatient clinics is 11.1%. In order to diagnose diabetes mellitus in the early stages, we suggest that oral glucose tolerance test, which is the gold standart for diagnosis of diabetes mellitus and the only way for the determination of impaired glucose tolerance, should be used. Besides, decreasing the lower limit of impaired fasting glucose to 100 mg/dL will help to identify intermittant hyperglycemia patients who are also called as prediabetics.