CBC with differential: isolated thrombocytopenia vs. multilineage involvement
Peripheral smear
(r/o pseudothrombocytopenia due to platelet clumping)
↑ destruction → look for large plts, ↑ MPV, schistocytes (see “Peripheral Smear” inserts)
↓ production → rarely limited to platelets → look for blasts, hypersegmented PMNs, leukoerythroblastic Δs; can see inclusion bodies (anaplasma), parasites (Babesia)
Additional laboratory evaluations as indicated
(eg, viral titers, flow cytometry, ANA, APLA)
if anemia: ✓ reticulocyte count, LDH, haptoglobin, bilirubin to detect hemolysis
if hemolytic anemia: ✓ PT, PTT, fibrinogen, D-dimer, Coombs, ANA
BM bx for unexplained thrombocytopenia, esp. if associated with splenomegaly