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)

Factors that affect the risk of developing HIT are noted as follows.^[1]

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.^[2] 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.

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

↑ Warkentin TE, Sheppard JA, Sigouin CS, Kohlmann T, Eichler P, Greinacher A. Gender imbalance and risk factor interactions in heparin-induced thrombocytopenia. Blood 2006;108:2937-41. PMID 16857993.
↑ ^2.0 ^2.1 ^2.2 Lee GM, Arepally GM (2013). "Diagnosis and management of heparin-induced thrombocytopenia". Hematol Oncol Clin North Am. 27 (3): 541–63. doi:10.1016/j.hoc.2013.02.001. PMC 3668315. PMID 23714311.