Evaluation and initial treatment of hospital-acquired thrombocytopenia in a non-pregnant adult

APS: antiphospholipid syndrome; aPTT: activated partial thromboplastin time; CAPS: catastrophic APS; CBC: complete blood count; DIC: disseminated intravascular coagulation; HIT: heparin-induced thrombocytopenia; PT: prothrombin time; TA-GVHD: transfusion-associated graft-versus-host disease; TTP: thrombotic thrombocytopenic purpura; VTE: venous thromboembolism.

* Before starting an extensive evaluation, confirm thrombocytopenia is real (not pseudothrombocytopenia due to platelet clumping) and new (not seen on previous CBCs). However, in a patient with clinically significant bleeding, treatment should not be delayed while obtaining these confirmations. Pseudothrombocytopenia can be excluded by repeating the platelet count using a collection tube with heparin or sodium citrate as the anticoagulant.

¶ Initially focus on common and "can't miss" (rare but potentially life-threatening) causes. Some of these may be present on admission but may not be appreciated until after the patient is admitted to the hospital.

• Common – Drug-induced and infection.
• Can't miss – Thrombotic microangiopathy such as TTP or drug-induced thrombotic microangiopathy; syndromes with thrombosis (HIT, DIC, APS, CAPS, or acute promyelocytic leukemia); TA-GVHD. A large VTE can cause thrombocytopenia, but new onset thrombocytopenia with thrombosis generally requires consideration of more serious causes such as HIT, DIC, APS, CAPS, or acute promyelocytic leukemia.

Δ Hemolysis is characterized by increased reticulocyte count, lactate dehydrogenase (LDH), and bilirubin, and decreased haptoglobin.