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Pharmacoepidemiol Drug Saf. 2017 Oct;26(10):1149-1155. doi: 10.1002/pds.4235. Epub 2017 May 24.

Immobilization and high platelet count are associated with thromboembolic complications in heparin-induced thrombocytopenia.

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Institute of Clinical Pharmacology and Toxicology, Charité - Universitätsmedizin Berlin, Berlin, Germany.
Department of Clinical Epidemiology, Leibniz Institute for Prevention Research and Epidemiology - BIPS, Bremen, Germany.
Institute of Social Medicine, Epidemiology and Health Economics, Charité - Universitätsmedizin Berlin, Berlin, Germany.
Frank Andersohn Consulting & Research Services, Berlin, Germany.
Institute of Transfusion Medicine, Charité - Universitätsmedizin Berlin, Germany.



Immune-mediated heparin-induced thrombocytopenia (HIT type II, HIT) is a potentially serious adverse drug reaction characterized by an increased risk of venous and arterial thrombosis. This study aimed to identify risk factors associated with the development of these complications.


Our study cohort included patients with HIT assembled in our pharmacovigilance center by reports from 51 collaborating hospitals in Berlin, Germany. To identify risk factors for thromboembolic complications, patients with thromboembolic events (cases) were compared to those without thromboembolic events (controls) in a case-control design. We applied univariable and multivariable logistic regression analysis to estimate odds ratios (OR) and corresponding 95% confidence intervals (CI) for potential risk factors of thromboembolic complications.


Our cohort comprised 209 HIT patients. Of those, 53 developed thromboembolic complications. Most HIT patients received heparin for medical indications (42.1%) or in the context of cardiovascular surgery (40.2%). Of the 78 thromboembolic complications, 49 (63%) and 29 (37%) were observed in the venous and arterial vascular bed, respectively. The main locations were deep vein thrombosis (39.7%), pulmonary embolism (16.7%), and limb artery thrombosis (16.7%). In multivariable analysis, immobilization prior to HIT (OR 4.6, 95% CI 1.2-18.0; P = .026) and higher platelet counts before initiation of heparin therapy (OR 1.004, 95% CI 1.000-1.008; P = .046) were independently associated with the occurrence of thromboembolic events.


Immobilization and a high platelet count (with a low effect size) are additional risk factors of thromboembolic complications in the course of HIT.


heparin-induced thrombocytopenia; pharmacoepidemiology; pharmacovigilance study; risk factors; thromboembolic complications

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