A 34-year-old man comes to the physician complaining of occasional dizziness and palpitations in crowded spaces. He is an executive who travels frequently and reports high stress levels at work. He takes no medications and his family history is unremarkable. He drinks alcohol occasionally and does not use tobacco or illicit drugs. His blood pressure is 130/80 mm Hg and pulse is 80/min. Chest examination is unremarkable. The liver span is 8 cm and the spleen is not palpable. There is no cervical lymphadenopathy or skin rash. Laboratory results are as follows:
Peripheral smear confirms a reduced platelet count without clumping or malignant cells. Which of the following is the most appropriate next test for this patient?

Question

A 34-year-old man comes to the physician complaining of occasional dizziness and palpitations in crowded spaces.  He is an executive who travels frequently and reports high stress levels at work.  He takes no medications and his family history is unremarkable.  He drinks alcohol occasionally and does not use tobacco or illicit drugs.  His blood pressure is 130/80 mm Hg and pulse is 80/min.  Chest examination is unremarkable.  The liver span is 8 cm and the spleen is not palpable.  There is no cervical lymphadenopathy or skin rash. Laboratory results are as follows:
 Peripheral smear confirms a reduced platelet count without clumping or malignant cells.  Which of the following is the most appropriate next test for this patient?

Quizplus · Accepted Answer

11ec25c8_d42f_01e0_bc81_03932c81344b_MD0003_00 This patient's presentation of isolated thrombocytopenia without anemia or leukopenia suggests idiopathic thrombocytopenia purpura (ITP). ITP is usually diagnosed after excluding other possible causes of thrombocytopenia based on history, physical examination, complete blood count, and peripheral blood smear. It is also important to rule out pseudothrombocytopenia due to platelet clumping by EDTA, abciximab administration, or inadequate anticoagulation of the blood sample. Thrombocytopenia can be due to increased platelet destruction, decreased platelet production, dilutional, or splenic sequestration (Table). Thrombocytopenia may be the presenting finding in up to 5%-10% of patients with chronic HIV infection. Therefore, all patients with presumed ITP should be tested for HIV and hepatitis C virus as platelet counts can be affected by treating the underlying disease. Bone marrow biopsy may be required in patients with negative tests and unexplained thrombocytopenia. chronic HIV infection (Choices A and F) The Schilling test historically was used to determine whether a patient had vitamin B12 deficiency due to pernicious anemia or a malabsorption syndrome. Blood folate levels are used to diagnose folic acid deficiency. Both folic acid and B12 deficiencies can cause pancytopenia (anemia, thrombocytopenia, and neutropenia). However, patients are often anemic and peripheral smear usually shows hypersegmented neutrophils. (Choice B) Computed tomography scan of the abdomen is indicated for evaluating splenomegaly in patients with suspected splenic sequestration of platelets (eg, cirrhosis, portal hypertension). However, this patient does not have splenomegaly or stigmata of liver disease (eg, spider angioma, caput medusa, gynecomastia, ascites). (Choice C) Epstein-Barr virus titers are useful for diagnosing infectious mononucleosis. Patients with infectious mononucleosis usually present with fatigue, sore throat, fever, palatal petechiae, posterior cervical lymphadenopathy, and splenomegaly. Laboratory testing shows lymphocytosis and possibly thrombocytopenia. However, this patient's thrombocytopenia without the other findings makes Epstein-Barr virus less likely. (Choice E) The rapid plasma reagin test is a nontreponemal antigen test used to screen for syphilis. Congenital syphilis can be associated with stillbirth, anemia, and thrombocytopenia. However, syphilis in adults is usually not associated with thrombocytopenia. Educational objective: Idiopathic thrombocytopenia purpura is usually diagnosed after excluding other possible causes of thrombocytopenia. These patients should be tested for hepatitis C and HIV as thrombocytopenia may be the initial presentation of HIV infection (up to 5%-10% of patients). Treatment of the underlying infection can affect the platelet count. References: The American Society of Hematology 2011 evidence-based practice guideline for immune thrombocytopenia. (http://www.ncbi.nlm.nih.gov/pubmed/21325604) Immune thrombocytopenic purpura: a presentation of HIV infection. (http://www.ncbi.nlm.nih.gov/pubmed/23087202)

A 34-Year-Old Man Comes to the Physician Complaining of Occasional