Which diagnostic test is used for confirming GDM, DM, and impaired glucose tolerance?

• A. 2HOGTT
• B. HbA1c
• C. Fasting plasma glucose
• D. Random plasma glucose

Answer: (A)

The test being evaluated is the one that reveals how well the body handles a standardized glucose load over time. The 2-hour oral glucose tolerance test involves giving a fixed amount of glucose and then measuring plasma glucose, typically at fasting and at about two hours afterward. This dynamic test directly shows post-load hyperglycemia, which is why it can diagnose diabetes, gestational diabetes, and impaired glucose tolerance.

Why this test fits best: fasting values can be normal even when the body isn’t clearing glucose properly after a meal, and HbA1c reflects average glucose over months rather than a specific post-load response. A 2-hour measurement after a glucose challenge captures how efficiently insulin and glucose metabolism respond in that moment, so it can identify DM when the two-hour value is clearly elevated, detect impaired glucose tolerance in the intermediate range, and diagnose gestational diabetes using pregnancy-specific thresholds.

Briefly, the other options don’t align with this post-load assessment: HbA1c may miss pregnancy-related changes and early post-load abnormalities, fasting plasma glucose may be normal in GDM or early DM, and random glucose lacks standardized diagnostic thresholds and doesn’t assess the body’s response to a glucose challenge.