[Definition and mechanism of drug-induced thrombocytopenia]

Drug-induced thrombocytopenia is common, but most previous reports do not present evidence for drugs as a definite or probable cause of the thrombocytopenia. The important diagnostic issue is to distinguish between drug-induced thrombocytopenia and idiopathic thrombocytopenic purpura, because the latter diagnosis requires the exclusion of other causes of thrombocytopenia. Drug-induced thrombocytopenia includes at least three mechanisms, such as marrow suppression, immunological, and nonimmunological thrombocytopenia. In immunological thrombocytopenia, demonstration of drug-dependent antiplatelet antibodies was included as evidence confirming the causal role of a drug. However, there are no standard assays for drug-dependent antiplatelet antibodies, no standard criteria for distinguishing positive from negative results, and no data on the sensitivity and specificity of these assays based on clinical criteria for a causal relation. Nonimmunological thrombocytopenia includes heparin-dependent thrombocytopenia and thrombotic thrombocytopenic purpura.