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Question 1 of 30

A 70-year-old man presents with weakness of his right arm and leg. His symptoms began yesterday and are now resolved. He also reports a 6-month history of recurrent headaches and fatigue. He is a nonsmoker. His medical history is significant for high blood pressure. His blood pressure is 167/88 mm Hg, his oxygen saturation is 93% on room air, his face is plethoric, and a right carotid bruit is heard. Other findings on physical examination are normal. Diagnostic testing results are shown in Table 9.Q5. Carotid ultrasonography shows a 30% stenotic lesion in the right carotid. The patient is hospitalized and begins antiplatelet therapy. Which of the following should you order next?

Rationale:
JAK2 V617F mutation testing should be ordered next. The patient's plethoric face, recurrent headaches, fatigue, and transient ischemic attack-like symptoms, coupled with unexplained hypoxemia (93% SpO2), strongly suggest a hyperviscosity syndrome potentially caused by polycythemia vera. While Table 9.Q5 is not provided, these clinical findings necessitate investigating a myeloproliferative neoplasm. The JAK2 V617F mutation is present in over 95% of polycythemia vera cases, making this the most appropriate and targeted diagnostic step to confirm the suspected underlying hematological disorder. B: Fluorescence in situ hybridization (FISH) for BCR-ABL testing This test primarily diagnoses chronic myeloid leukemia, which typically presents with splenomeg