American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the preferred test for diagnosing posttransplantation diabetes mellitus?

1. Fasting glucose test

2. Oral glucose tolerance test

3. A1C test

4. Random glucose test

The correct answer is: Oral glucose tolerance test

The preferred test for diagnosing posttransplantation diabetes mellitus is the oral glucose tolerance test (OGTT). This test is particularly suitable in this context because it effectively evaluates how the body processes glucose under a controlled condition, providing insights into insulin sensitivity and overall glucose metabolism. Posttransplantation diabetes mellitus often develops due to a combination of factors, including the effects of immunosuppressive medications, which can lead to insulin resistance and impaired glucose tolerance. The OGTT involves measuring blood glucose levels after fasting and then again two hours after consuming a glucose-rich beverage. This two-step process can detect abnormalities that may not be evident with single measurements of glucose levels, as it accounts for the body's glucose handling during a dynamic state. While fasting glucose tests, A1C tests, and random glucose tests are valuable in various diagnostic contexts, they may not fully capture the nuances of glucose metabolism post-transplant. Fasting tests can miss the fluctuations that occur after glucose ingestion, and A1C may not be as reliable in patients with conditions affecting red blood cell turnover or those who have had recent blood transfusions, which can skew results. Random glucose tests can indicate hyperglycemia but do not provide a comprehensive assessment of glucose tolerance. Given these considerations, the oral glucose