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

A. Serum ketone bodies estimation
B. Serum insulin estimation
C. Serum glucose tolerance test (GTT)
D. Serum fructosamine estimation

**Correct Answer:** C. Serum glucose tolerance test (GTT)

**Core Concept:**

The Benedict's test is a qualitative test used to detect the presence of reducing sugars in biological samples such as urine or blood. In this scenario, the positive result indicates an increased level of glucose in the sample. The elevated random blood sugar (163 mg%) and fasting blood sugar (200 mg%) further confirm glucose hyperglycemia.

**Why the Correct Answer is Right:**

Given the patient's clinical presentation, the next line of investigation should focus on assessing the patient's glucose tolerance. A glucose tolerance test (GTT) is a comprehensive test that measures how well the body is regulating blood sugar levels over time. The test involves fasting the patient for a period, then administering a glucose load and measuring blood glucose levels at different time points. In this case, the GTT will help identify the type of diabetes (e.g., type 1 or type 2) and provide valuable information about the patient's glucose homeostasis.

**Why Each Wrong Option is Incorrect:**

A. Serum ketone bodies estimation: This test is used to assess ketone body levels in the blood, which are typically elevated in diabetic ketoacidosis (DKA). Since the patient does not exhibit signs of DKA (e.g., acidosis, dehydration, and ketones in the urine), this test is not relevant.

B. Serum insulin estimation: Insulin estimation is used to determine the patient's insulin levels. In this scenario, elevated insulin levels would be more indicative of hypoglycemia rather than hyperglycemia. Moreover, insulin estimation is not a standard test for assessing glucose tolerance.

C. Serum fructosamine estimation: Fructosamine estimation is used to assess the average blood glucose levels over the past 2-3 weeks. While this test is important, it is not the next immediate test to perform after confirming hyperglycemia. In contrast, a GTT is more suitable for determining the patient's glucose homeostasis and identifying the type of diabetes.

D. Serum fructosamine estimation: Similar to explanation for option B, insulin estimation is not relevant in this context as it is more indicative of hypoglycemia and not helpful in assessing glucose tolerance. Additionally, serum fructosamine estimation is not the first step in evaluating glucose tolerance after confirming hyperglycemia.

**Clinical Pearls:**

1. A GTT is the most appropriate test to determine the patient's glucose homeostasis and identify the type of diabetes.
2. Insulin estimation is not relevant in assessing glucose tolerance and is more indicative of hypoglycemia.
3. Serum fructosamine estimation is not the first step in evaluating glucose tolerance