A Clinical Scoring System for Predicting Heparin-Induced Thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is often suspected in acutely ill patients receiving heparin, but deciding which patients should undergo testing and receive alternative anticoagulants can be challenging. A potentially useful pretest clinical algorithm for predicting HIT is the 4Ts scoring system. Points are awarded for thrombocytopenia (2 points if >50% decline in platelet count and nadir ≥20,000/μL), timing of platelet count decline (2 points if onset occurs 5–10 days after exposure to heparin or ≤1 day if prior heparin exposure occurred within 30 days), thrombosis (2 points if new onset, skin necrosis, or acute systemic reaction), and other causes of thrombocytopenia (2 points if none apparent). No points are given if the platelet …