In a previously unexposed patient, when does the platelet count fall in heparin-induced thrombocytopenia (HIT)?A. <24 hours
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.