What is HIT? “Heparin-induced thrombocytopenia (HIT)”
It is a side effect of heparin treatment that causes thrombocytopenia (low platelet count). HIT may be classified into two parts. In most cases, type 1 HIT manifests itself during the first 2 days after being exposed to heparin, and the platelet count returns to normal with continuous heparin treatment.
HIT type 1
Type 1 HIT is a non-immune disease that develops as a consequence of the direct impact of heparin on the activation of platelet cells.
HIT type 2
A type 2 HIT is an immune-mediated disease that usually manifests itself 4-10 days after exposure to heparin and is associated with life- and limb-threatening thrombotic events. Type 2 HIT is more common in women than in men. When the word HIT is used in normal medical practice, it refers to type 2 HIT.
4 t score
How to Calculate HIT 4T Score
Check for thrombocytopenia, platelet count and nadir.
Check for time required for platelet count to fall.
Check for thrombosis, skin necrosis, or acute systemic reaction.
Review other causes for thrombocytopenia.
HIT 4T Score Calculator
The HIT 4Ts is an algorithm to help in the diagnosis HIT of patients who develop thrombocytopenia in the clinical environment.
Scoring system consisted of four criteria, each of which was worth 0, 1, or 2 points.
Study used ≤ 3 points to define low probability group (≤5%) for HIT, 4-5 points for intermediate and 6-8 points for high.