Lacey and Penner listed criteria for the diagnosis of idiopathic thrombocytopenic purpura (ITP) in an adult. The authors are from the University of Michigan.


Criteria for the diagnosis of ITP in the adult - all of the following:

(1) thrombocytopenia, with platelet count <= 50,000 per µL

(2) increased megakaryocytic mass seen on bone marrow biopsy

(3) absence of the following:

(3a) splenomegaly

(3b) disseminated intravascular coagulopathy (DIC)

(3c) thrombotic thrombocytopenic purpura (TTP) or hemolytic-uremic syndrome (HUS)

(3d) post-transfusion purpura

(3e) hematologic or lymphoreticular malignancy

(3f) systemic lupus erythematosus (SLE)

(3g) hemolytic anemia with or without accompanying leukopenia

(3h) infection-related thrombocytopenia (infectious mononucleosis, CMV, etc.)

(3i) drug-induced thrombocytopenia (immune or direct toxicity)

(4) presence of anti-platelet antibodies



• The presence of splenomegaly suggests a secondary form of thrombocytopenia.

• The diagnosis may be made in the absence of anti-platelet antibodies is the testing is unavailable or delayed.

• ITP may follow a viral infection due to a post-infectious immune response rather than a direct effect of the virus.


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