Efficacy and safety analysis of using a lower platelet threshold for warfarin initiation in patients with heparin-induced thrombocytopenia

Anastasiya Plagova*

Objectives: To determine efficacy and safety of warfarin initiation in patients with confirmed heparin-induced thrombocytopenia (HIT) at a lower platelet threshold (less than 150x109/L) versus 150x109/L platelet threshold. Methods: This is a multi-center, retrospective, cohort study. Patients were divided into two groups based on platelet threshold at warfarin initiation in order to evaluate efficacy and safety of using a lower platelet threshold for transitioning patients from parenteral anticoagulation to warfarin. The primary outcome was the incidence of a new symptomatic thrombosis following warfarin initiation. Safety outcomes included major bleeding and incidence of thrombosis. Results: None of the patients in either group had a VTE within 30 days of warfarin. Hospital length of stay was shorter in the lower platelet threshold group at 21 days compared to 25 days in the latter group (P-value: 0.413). Transitioning to warfarin sooner was associated with an increase in major bleeding: 4 patients (33%) compared to 1 patient (6%), (P-value=0.133), respectively. Conclusion: The data suggests that initiating warfarin at a lower platelet threshold does not affect rate of thrombosis or mortality, but may be associated with an increased risk in major bleeding. Patients with HIT should be transitioned to warfarin when the platelet count is at least 150 x109/L