281) A 22 year old woman is seen in the office for a rash on legs. She had an upper respiratory tract infection one week ago which resolved spontaneously. She is not on any medications. She has no other significant mast medical history. She has easy bruising which started 5 days ago but denies any nose bleeds or gross bleeding. Her last menstrual period was one week ago and she has regular cycles with no history of menorrhagia. Family history is negative for any bleeding disorders or thrombocytopenia. She denies any smoking , alcohol or drug abuse. Physical examination is benign except for petechiae on her bilateral lower extremities. There is no splenomegaly on examination. Laboratory investigations reveal:
Hemoglobin 14 g/dL,
Mean cell volume (MCV) 84 fL
Platelet count 18k/µl
Liver function tests, Electrolytes, Creatinine, Prothrombin time and Partial thromboplastin time are within normal limits. A peripheral blood smear shows reduced number of platelets with out any schistocytes or blasts or nucleated red cells. Antinuclear antibodies, HIV testing and Hepatitis C are negative.
Which of the following is the most appropriate next step in managing this patient?
A) Ristocetin cofactor assay
D) Bone marrow biopsy
F) Platelet transfusion