[Biological diagnosis and surveillance of heparin-induced thrombopenia]

THE CHALLENGE: Heparin-induced thrombocytopenia is a diagnostic challenge for the clinician. Currently, it is recommended to monitor platelet counts for the first 3 weeks of heparin therapy. Laboratory counts often may drop off before any evidence of a clinical manifestation.

Confirming the diagnosis of heparin-induced thrombocytopenia's often difficult during the acute phase. The most widely used tests evidence a platelet activator or proaggregate effect when the patient's plasma or serum is exposed to heparin. In France, the platelet aggregation test is used almost exclusively although release of labeled serotonin is considered to be the reference technique. The antigenic target of antibodies produced in heparin-induced thrombocytopenia are identified by their constituent platelet factor 4 and heparin sulfate chains. A commercial immunological kit is based on this principle. SUBSTITUTION TREATMENT: The laboratory's contribution goes beyond positive diagnosis of heparin-induced thrombocytopenia. Indeed, disseminated intravascular coagulation must be recognized and a substitution treatment proposed together with a measuring the activated partial thromboplastia time.