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Test yourself: Thrombocytopenia

From the July ACP Hospitalist, copyright © 2010 by the American College of Physicians

The following case and commentary, which address thrombocytopenia, are excerpted from ACP's Medical Knowledge Self-Assessment Program (MKSAP 15).

Headache, fatigue and gingival bleeding

A 27-year-old woman is evaluated in the emergency department for a two-day history of diffuse headache, fatigue and gingival bleeding on brushing her teeth. She is otherwise healthy. Her only medication is an oral contraceptive, and medical and family histories are unremarkable.

On physical examination, she is alert and oriented but reports having a headache. Funduscopic examination is normal. There are a few scleral hemorrhages, and mild icterus is noted. Petechiae that had gone unnoticed by the patient are visible on the lower extremities. Cardiopulmonary and abdominal examinations are normal.

Laboratory studies indicate a hemoglobin level of 8 g/dL (80 g/L); platelet count of 34,000/µL (34 × 10⁹/L); reticulocyte count of 12% of erythrocytes; international normalized ratio (INR) of 1.1; activated partial thromboplastin time (aPTT) of 32 seconds; thrombin time of 16 seconds (control time of 15 seconds); lactate dehydrogenase of 2,000 U/L; serum creatinine of 0.8 mg/dL (61 µmol/L); and a negative D-dimer assay.

A peripheral blood smear is pictured.

Q: Which of the following is the most appropriate next step in management?

A. aPTT mixing study
B. Direct antiglobulin (Coombs) test
C. Intravenous immune globulin
D. Plasma exchange
E. Platelet antibody test

Answer and Commentary

Correct answer: D. Plasma exchange.

This patient has evidence of microangiopathic hemolytic anemia, thrombocytopenia with normal coagulation, and central nervous system symptoms, the principal triad of thrombotic thrombocytopenic purpura (TTP); renal failure and fever compose the pentad of symptoms. Plasma exchange is the principal treatment modality for TTP and should be initiated as soon as possible to decrease patient morbidity. Plasma exchange reverses the platelet consumption that is responsible for the thrombus formation causing the findings associated with TTP. It is acceptable to initiate plasma exchange even in circumstances when the diagnosis is in question, only to be stopped when an alternative diagnosis is established.

Intravenous immune globulin is useful in treating patients with immune thrombocytopenic purpura (ITP) but not TTP. The presence of severe microangiopathic hemolytic anemia is inconsistent with ITP and, therefore, precludes the use of intravenous immune globulin in this patient.

A direct antiglobulin (Coombs) test would be appropriate for patients with suspected immune hemolytic anemia, but this is a case of microangiopathic hemolytic anemia as evidenced by schistocytes on the peripheral blood smear.

An activated partial thromboplastin time (aPTT) mixing study is not indicated in this patient because her aPTT is normal.

Platelet antibody assays are generally not very sensitive or specific in patients with thrombocytopenia and would not be helpful in this case. A positive test result would not explain the presence of schistocytes on the peripheral blood smear.

Key Point Microangiopathic hemolytic anemia, thrombocytopenia with normal coagulation, and central nervous system symptoms are the principal triad of thrombotic thrombocytopenic purpura; renal failure and fever compose the pentad of symptoms.

The information included herein should never be used as a substitute for clinical judgment and does not represent an official position of ACP. Click here for more information on MKSAP 15.

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ACP Hospitalist provides news and information for internists about the practice of medicine and reports on the policies, products and activities of ACP. All published material, which is covered by copyright, represents the views of the contributor and does not reflect the opinion of the American College of Physicians or any other institution unless clearly stated