4T Score Calculator

Calculate the 4Ts Score for HIT

The 4Ts score estimates the probability of heparin induced thrombocytopenia (HIT) using thrombocytopenia severity, timing relative to heparin, thrombosis signs, and alternative explanations. Clinicians use it alongside lab testing, not as a standalone diagnosis. For related blood work tools, see the ANC Calculator and BUN to Creatinine Ratio Calculator.

Four Scoring Domains

Each domain awards 0, 1, or 2 points. Thrombocytopenia evaluates platelet fall and nadir. Timing checks whether the drop aligns with typical HIT windows after heparin exposure. Thrombosis captures new clotting events or skin findings. Other causes subtract points when a clear alternative diagnosis exists.

Interpreting Total Points

Low scores suggest low probability, intermediate scores warrant further evaluation, and high scores support urgent workup while heparin is held. Always correlate with serotonin release assay or other institutional protocols.