Heparin-induced thrombocytopenia risk factors


 * Associate Editor-In-Chief:, Aric C. Hall, M.D., [mailto:achall@bidmc.harvard.edu]

Overview
Heparin-induced thrombocytopenia is diagnosed when the platelet count falls by > 50% typically after 5-10 days of heparin therapy. Increased risks for heparin-induced thrombocytopenia depends on type of heparin (unfractionated heparin > low molecular weight heparin), duration of therapy, females and type of patients (commoner in surgical patients that require large amount of heparin)

Risk factors

 * Genetic risk factors for thrombosis such as factor V Leiden, prothrombin gene mutation, methylenetetrahydrofolate reductase (MTHFR) polymorphism and platelet-receptor polymorphisms do not increase the risk of developing HIT associated thrombosis.
 * Factors that affect the risk of developing HIT are noted as follows.
 * Duration of heparin treatment; long duration, up to 2 weeks is associated with the greatest risk.
 * The type of heparin involved; unfractionated heparinUFH has a greater risk than low molecular weight heparin LMWH.
 * The type of patient; surgical patients are at higher risk than medical; cardiac surgical patients have the highest risk of all.
 * Females have a higher risk.