Purpose of review: This review addresses the clinical and biological strategy to be applied for the diagnosis of heparin-induced thrombocytopenia.
Recent findings: Heparin-induced thrombocytopenia is a severe prothrombotic disease caused by immunoglobulin G antibodies, which bind to platelet factor 4 and activate platelets with subsequent increased thrombin generation. Venous and arterial thromboses are frequent, explaining why substituting heparin with a potent alternative anticoagulant (danaparoid, lepirudin, or argatroban) is necessary in every affected patient. However, the diagnosis of heparin-induced thrombocytopenia is often difficult and it has to be diagnosed on the basis of clinical criteria and reliable laboratory tests (immunoassays and platelet activation tests). The profiles of platelet count evolution suggestive of heparin-induced thrombocytopenia in cardiac surgery patients are now well defined. For other clinical settings, the usefulness of a scoring system, the '4Ts', estimating the probability of heparin-induced thrombocytopenia before laboratory testing, combined with one immunoassay allowing specific detection of heparin-induced thrombocytopenia antibodies, has been recently documented.
Summary: Recent studies have demonstrated the usefulness of combining a pretest clinical score (4Ts) and biological assays to diagnose heparin-induced thrombocytopenia and the algorithms that have to be applied for clinical practice are now better defined.