A 24-year-old woman has a low platelet count on routine blood work. She denies bleeding, fever, chills, weight loss, bone pain, or abdominal pain. Her past medical history is unremarkable and she does not take any medications. She does not use tobacco, alcohol, or illicit drugs. She is sexually active.
Complete physical examination is within normal limits.
Laboratory results are as follows:

Blood smear shows a paucity of platelets but is otherwise unremarkable. Pregnancy test is negative.
Which of the following is the best next step in managing this patient?

Question

A 24-year-old woman has a low platelet count on routine blood work.  She denies bleeding, fever, chills, weight loss, bone pain, or abdominal pain.  Her past medical history is unremarkable and she does not take any medications.  She does not use tobacco, alcohol, or illicit drugs.  She is sexually active.
Complete physical examination is within normal limits.
Laboratory results are as follows:

Blood smear shows a paucity of platelets but is otherwise unremarkable.  Pregnancy test is negative.
Which of the following is the best next step in managing this patient?

Quizplus · Accepted Answer

This patient presents with asymptomatic thrombocytopenia, possibly from immune thrombocytopenic purpura (ITP). However, secondary causes should be ruled out prior to making the diagnosis of ITP. This requires a thorough history, physical examination, complete blood count, and examination of the peripheral blood smear. The only additional tests recommended in patients with presumptive ITP include HIV and HCV testing, as treatment of these underlying diseases may alter the course of secondary ITP. Bone marrow aspiration is also recommended in patients > age 60 to rule out myelodysplastic syndromes. Thrombocytopenia can be the initial presenting feature in up to 10% of HIV patients, and occurs in up to 40% of patients during the course of their illness. As a result, this patient should undergo HIV testing and possibly hepatitis C testing (if risk factors are present) (Choice D). (Choice A) It is important to stress that the diagnostic criteria for ITP emphasize excluding only clinically apparent associated conditions. For example, approximately 40% of patients with apparently isolated ITP have positive tests for ANA antibodies. Yet only a subset of these patients go on to develop SLE, with no correlation between the titer of ANA antibodies and the risk of developing SLE. Therefore, further serologic testing is not warranted in patients with isolated ITP unless they develop further signs and symptoms of SLE. (Choice B) Flow cytometry helps evaluate for hematologic or lymphoid malignancy (e.g., acute leukemia), but this patient's otherwise normal peripheral smear makes this less likely. Lymphoma usually requires tissue biopsy for diagnosis. (Choice E) Serum electrophoresis is useful for identifying monoclonal disorders (e.g., multiple myeloma, plasma cell dyscrasias), which can present with thrombocytopenia in approximately 5% of patients. This patient's absence of anemia, bone pain, renal disease, fatigue, or hypercalcemia makes this consideration less likely. Educational objective: Patients with isolated thrombocytopenia should undergo thorough evaluation to rule out secondary causes (e.g., drugs and infections), which includes HIV testing and possible hepatitis C testing. Patients with negative results on both of these studies are presumed to have ITP. __________ References: Reviewed diagnosis of primary and secondary immune thrombocytopenic purpura in 79 adult patients hospitalized in 2000-2002 (http://www.ncbi.nlm.nih.gov/pubmed/20962625) An overview of the mechanisms of HIV-related thrombocytopenia (http://www.ncbi.nlm.nih.gov/pubmed/20606410)

A 24-Year-Old Woman Has a Low Platelet Count on Routine