Diagnosis of HIT based on score:

0-3 points, low suspicion: very low probability of HIT diagnosis;

4-5 points, moderate suspicion: 0.6% probability of HIT diagnosis if antibody negative, 58.2% if antibody positive;

6-8 points, high suspicion: 16% probability of HIT diagnosis if antibody negative, 98% if antibody positive.

The HIT 4Ts scoring system has a high negative predictive value. Clinically, the 4T scoring system is used first to evaluate the likelihood of HIT. If there is a high or moderate suspicion of HIT, appropriate laboratory tests should be conducted to confirm or exclude HIT. If there is only a low suspicion, the necessity of laboratory tests to confirm or exclude the diagnosis is still debated.