A 42 year old male has strong positive Benedict's test, random blood sugar is > 163 mg%, fasting blood sugar is > 200mg%. Next line of investigation is:

Answer is B (Oral GTT): Oral glucose tolerance test (Oral GTT) should be performed when the diagnosis of diabetes is in doubt The patient in question has a random blood glucose of 163 mg/dl which is lower than the required level (200 mg/dl) to consider diabetes. He however has a fasting blood glucose level of 200mg/d1 which is well above the desired level (126 mg/dl) to consider diabetes. Although fasting blood glucose is the more reliable test for ident5ing DM, and diabetes may be diagnosed with a fasting blood glucose > 126mg/d1 such diagnosis should not be made if only a single fasting blood glucose meets the criterion. The next best step is either to repeat the test on a different day (preferred) or perform an oral GTT. As the option of repeating 'fasting blood glucose' is not provided in the question, performing an oral GTT becomes the single best answer of exclusion. Criteria for the diagnosis of diabetes mellitus Symptoms of diabetes plus random blood glucose concentration > 11.1 mmol/L (200mg/dL) Fasting plasma glucose > 7.0 mmol/L (126 mg/dL) or Two-hour plasma glucose > 11.1 mmol/L (200 mg/dL) during an oral glucose tolerance test. Note: In the absence of unequivocal hyperglycemia and acute metabolic decompensation, these criteria should be confirmed by repeat testing on a different day.