- History or clinical evidence of medical conditions felt to be the underlying cause of their thrombocytopenia. Such conditions commonly include systemic lupus erythematosus, history of chronic lymphocytic leukemia, dysplasia, agammaglobulinemia, treatment with heparin, quinidine, quinine, trimethoprim-sulfamethoxazole, or ticlopidine or any other drug thought to be the cause of patient's thrombocytopenia, congenital or hereditary thrombocytopenia, or pseudothrombocytopenia (clumping on peripheral blood smear)