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Question 5#

In a previously unexposed patient, when does the platelet count fall in heparin-induced thrombocytopenia (HIT)?

A. <24 hours
B. 24-28 hours
C. 3-4 days
D. 5-7 days

Correct Answer is D


Heparin-induced thrombocytopenia (HIT) is a form of drug-induced immune thrombocytopenia (ITP). It is an immunological event in which antibodies against platelet factor-4 (PF4) formed during exposure to heparin, affecting platelet activation and endothelial function with resultant thrombocytopenia and intravascular thrombosis. The platelet count typically begins to fall 5 to 7 days after heparin has been started, but if it is a re-exposure, the decrease in count may occur within 1 to 2 days.