Heparin-induced thrombocytopenia associated with interleukin-8-dependent platelet activation in a patient with antiphospholipid syndrome.

Platelet factor 4 heparin enzyme immunoassay, platelet aggregation test, and serotonin release assay are commonly used to diagnose and confirm heparin-induced thrombocytopenia. We describe a case of recurrent thrombocytopenia appearing in a few hours after each heparin administration and who tested negative for the three assays. Further analysis revealed anti-interleukin (IL)-8 antibodies and IL-8-dependent platelet activation facilitated by heparin, which may explain this unusual case of heparin-induced thrombocytopenia.