American Board of Internal Medicine (ABIM) Certification Practice Exam

What is one of the key indicators for assessing TTP beyond clinical diagnosis?

1. ADAMTS-13 inhibitor titer

2. Blood pressure measurement

3. CT scan of the abdomen

4. Liver function tests

The correct answer is: ADAMTS-13 inhibitor titer

The key indicator for assessing Thrombotic Thrombocytopenic Purpura (TTP) beyond clinical diagnosis is the measurement of ADAMTS-13 inhibitor titer. TTP is characterized by a deficiency of the ADAMTS-13 enzyme, which is crucial for the breakdown of von Willebrand factor (vWF). In TTP, the activity of this enzyme is significantly reduced or absent, leading to the formation of large vWF multimers and subsequent microangiopathic hemolytic anemia and thrombocytopenia. Testing for ADAMTS-13 levels and determining the presence of inhibitors is essential for confirming the diagnosis of TTP. A severely reduced activity of ADAMTS-13, along with the presence of inhibitory antibodies, helps to establish the condition and differentiate it from other thrombotic microangiopathies. This test is particularly important given that the management of TTP involves therapeutic plasma exchange, and early and accurate diagnosis is crucial for patient outcomes. Other options, while potentially useful in different contexts, do not specifically provide definitive evidence for diagnosing TTP. Blood pressure measurements can indicate hypertensive crises but do not inform about the underlying hemostatic dysfunction. A CT scan of the abdomen might be useful in assessing