Heparin-induced thrombocytopenia among patients of a comprehensive cancer center.

Most clinical studies of heparin-induced thrombocytopenia have not included cancer patients who have high risk of thromboembolism, frequent exposure to heparin, and many potential causes of thrombocytopenia other than heparin-induced thrombocytopenia. To estimate the incidence and prevalence of heparin-induced thrombocytopenia in cancer patients, we identified cases based on diagnostic codes, anti-heparin antibody testing, and clinical characteristics (4T score) at a comprehensive cancer center between 1 October 2008 and 31 December 2011. We estimated that the prevalence of heparin-induced thrombocytopenia to be 0.02% among all cancer patients and 0.24% among cancer patients exposed to heparin. The annual incidence of heparin-induced thrombocytopenia was 0.57 cases per 1000 cancer patients exposed to heparin. Of the 40 cancer patients with the International Classification of Diseases (Ninth Revision; ICD-9) code for heparin-induced thrombocytopenia, positive anti-heparin antibody, and 4T score ≥4, 5 (12.5%) died of related thromboembolic or hemorrhagic complications. In a multivariate logistic regression model, male gender was a significant (p = 0.035) factor, and non-hematological malignancy was a significant (p = 0.017) factor associated with anti-heparin antibody positivity. Future studies may further examine the risk factors associated with heparin-induced thrombocytopenia in larger cohorts.