Key Takeaways

✅ Suspect heparin-induced thrombocytopenia (HIT) in a patient with new onset moderate thrombocytopenia with or without thrombosis in temporal association with initiation of heparin therapy.

✅ HIT-associated thrombosis may occur in blood vessels of any size.

✅ Calculate the 4T score. If low probability (3 or lower), continue heparin and do not order an immunoassay. If moderate-high probability (4 or higher), immediately stop all heparin products, start a non-heparin anticoagulant, and order an immunoassay.

✅ Consider using a DOAC in patients who are not at high risk of bleeding and do not have massive clot burden.

✅ Stop and reverse vitamin K antagonist if patient taking at time of HIT suspicion.

✅ Do not administer prophylactic platelet transfusion and avoid routine use of IVC filters.

✅ If the immunoassay assay is negative, HIT is ruled out. May revert to heparin treatment for original indication.

✅ If the immunoassay assay is positive, continue to avoid all heparin products, continue to administer non-heparin anticoagulant, and obtain a serotonin release assay.

✅ If serotonin release assay is negative, stop non-heparin anticoagulant and resume heparin.

✅ If serotonin release assay is positive, continue non-heparin anticoagulant until platelet count recovers, then switch to coumadin (with appropriate overlap), or preferably a DOAC and treat for 4-6 weeks (if no thrombosis) or 3 months (if thrombosis).