Prevalence and Risk of Pre-existing Heparin-induced Thrombocytopenia Antibodies in Patients with Acute Venous Thromboembolism.
Chest. 2011 Mar 10;
Authors: Warkentin TE, Davidson BL, Buller HR, Gallus A, Gent M, Lensing AW, Piovella F, Prins MH, Segers AE, Kelton JG
Abstract BACKGROUND: Some patients with acute venous thromboembolism who may previously have been exposed to heparin products have unrecognized antibodies implicated in heparin-induced thrombocytopenia (HIT). Antibody prevalence and patient consequences upon exposure to heparin, low-molecular-weight heparin, and fondaparinux are uncertain. METHODS: In this secondary analysis, we tested patients in the Matisse venous thromboembolism studies at study entry for heparin-dependent antibodies and further tested ELISA-positive patients for platelet-activating antibodies. We compared the risk of HIT (>50% platelet count fall, heparin-dependent antibodies, no contradicting features) between those treated with heparin (either unfractionated or low-molecular-weight [enoxaparin]) versus those who received fondaparinux. Comparison groups for thrombocytopenia occurrence were ELISA-positive, platelet-activating antibody-positive patients, ELISA-positive but platelet-activating antibody-negative patients, and randomly-selected antibody-negative patients. RESULTS: 127 (3.2%) of 3994 patients were ELISA-positive at baseline but only 14 (0.4%; 95% CI, 0.2-0.6%) had platelet-activating antibodies. Among these 14, four treated with unfractionated or low-molecular-weight heparin developed HIT, compared to none of 10 fondaparinux-treated patients (OR 95, 95% CI, 8-1123; p<0.001). This frequency (4/4, 100%) significantly differed from that of both heparin-treated patients who were ELISA-positive but platelet-activating antibody-negative, and from heparin-treated antibody-negative controls (0/15 and 0/27, respectively; p<0.001 for both). CONCLUSION: 0.4% of patients with venous thromboembolism had pathologic platelet-activating heparin-dependent antibodies, rather than the 3.2% detected by the commercial ELISA's recommended cut-off. Among study patients with acute venous thromboembolism who have platelet-activating antibodies, treatment with fondaparinux reduces the risk of precipitating rapid-onset HIT.
PMID: 21393394 [PubMed - as supplied by publisher]