American Board of Internal Medicine (ABIM) Certification Practice Exam

Which test is recommended to diagnose essential thrombocythemia?

1. Bone marrow aspiration

2. JAK2 V617F mutational analysis

3. Complete blood count

4. Serum iron levels

The correct answer is: JAK2 V617F mutational analysis

JAK2 V617F mutational analysis is recommended to diagnose essential thrombocythemia because this mutation is commonly associated with myeloproliferative neoplasms, including essential thrombocythemia. The presence of the JAK2 V617F mutation can provide supportive evidence of the disease in patients who present with an elevated platelet count and other clinical symptoms typical of essential thrombocythemia. This test is crucial as almost half of the patients with essential thrombocythemia will harbored this mutation, making it a significant marker in the diagnosis. While bone marrow aspiration can be used to assess the overall marrow activity and rule out other conditions like myelodysplastic syndromes or other causes of thrombocytosis, it is not a definitive stand-alone test for essential thrombocythemia and might not reveal the specific genetic mutation. A complete blood count is often the first step in evaluation and can indicate elevated platelet levels, but it lacks the specificity needed for a diagnosis. Serum iron levels are not relevant in the context of diagnosing essential thrombocythemia and would not provide useful information about this condition. Thus, the focus on JAK2 V617F mutational analysis highlights the importance of targeted genetic tests in confirming the diagnosis of essential