September 9, 2021Published by TDP on September 9, 2021Categories CalculatorsHow to Calculate HIT 4T ScoreHow to Calculate HIT 4T Score. Heparin-induced thrombocytopenia (HIT) Heparin-induced thrombocytopenia (HIT) is a rare but serious blood clotting disorder that can develop after you've been treated with heparin.