HIT 4T score is a rating used to help clinicians
Evaluation of pretest clinical score (4 T’s) for the diagnosis of heparin-induced thrombocytopenia in two clinical settingsG K Lo , D Juhl, T E Warkentin, C S Sigouin, P Eichler, A Greinacher
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.
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.
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.
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.