Heparin-induced thrombocytopenia risk factors

Heparin-induced thrombocytopenia
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2], Aric C. Hall, M.D., [3] Shyam Patel [4]

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

Adverse risk factors include:

• Duration of heparin treatment: long duration, up to 2 weeks is associated with the greatest risk.
• Type of heparin: unfractionated heparin (UFH) has a greater risk than low molecular weight heparin (LMWH.
• Type of patient: surgical patients are at higher risk than medical; cardiac surgical patients have the highest risk of all. This is though to be related to differences in basal level of circulating platelet factor 4 (PF4) and platelet activation in these various populations.
• There is no increase in risk of HIT with genetic risk factors for thrombosis such as factor V Leiden, prothrombin gene mutation, methylenetetrahydrofolate reductase (MTHFR) polymorphism and platelet-receptor polymorphisms.

all.

• Sex: Females have a higher risk than males. The odds ratio (OR) is 2.4:1.
• Race: African Americans are more prone to HIT than Caucasians.

Protective risk factors include:

• Use of low molecular weight heparin
• Type of patient: Pediatric or obstetric patients have a lower risk than medical or surgical patients