Very low platelet counts in post-transfusion purpura falsely diagnosed as heparin-induced thrombocytopenia: Report of four cases and review of literature

Differential diagnosis between post-transfusion purpura (PTP) and heparin-i nduced thrombocytopenia (HIT) can be difficult in the initial stages of thr ombocytopenia, as the early clinical presentations are often similar. Four patients are described who were suspected clinically of suffering from HIT. All four patients had recent blood transfusions and platelet alloantibodie s, thus the diagnosis of PTP was made. One lethal gastrointestinal and one retroperitoneal hemorrhage developed in two of the four patients. Unusually , one patient was male and two different platelet alloantibodies were prese nt in his serum; in another patient platelet alloantibodies and HIT-antibod ies were detectable. To arrive at the right diagnosis as quickly as possibl e is vitally important since treatment, which has to be initiated promptly, is very different for the two syndromes. Thus, we suggest that in patients where HIT is suspected, additional information should be sought. If featur es consistent with PTP (such as a recent blood transfusion or a marked drop in platelet count to below 15 Gpt/L) are present, we recommend parallel te sting for platelet alloantibodies to rule out PTP. (C) 2000 Elsevier Scienc e Ltd. All rights reserved.