HIT 4Ts Score for Heparin-Induced Thrombocytopenia

Calculates the 4Ts pretest probability score for heparin-induced thrombocytopenia (HIT) based on thrombocytopenia severity and timing, thrombosis or other sequelae, and other causes of thrombocytopenia. Score 0–8; ≥4 warrants investigation.

Weight
Height
Clinical Guidance

BMI is a screening measure of body size, not a direct measure of body fat. The standard WHO categories are underweight (<18.5), normal (18.5–24.9), overweight (25–29.9), and obese (≥30).

BMI can overestimate body fat in athletes with high muscle mass and underestimate it in older adults with low muscle mass. Interpret it alongside waist circumference and clinical context rather than as a standalone diagnosis.

⚕ Clinical Disclaimer: These calculators are for educational and reference purposes only. Always verify results with qualified clinical judgment and current clinical guidelines. Do not use as a sole basis for medical decisions.
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How It Works

Calculates the 4Ts pretest probability score for heparin-induced thrombocytopenia (HIT) based on thrombocytopenia severity and timing, thrombosis or other sequelae, and other causes of thrombocytopenia. Score 0–8; ≥4 warrants investigation

Each component has a specific meaning:

  • Thrombocytopenia severity — The thrombocytopenia severity recorded for the scenario being assessed.
  • Timing — The timing recorded for the scenario being assessed.
  • Thrombosis or other sequelae — The thrombosis or other sequelae recorded for the scenario being assessed.
  • Other causes of thrombocytopenia — The other causes of thrombocytopenia recorded for the scenario being assessed.

Note: Interpret the hit 4ts score result against the thresholds and context described above.

How to Use

Enter the thrombocytopenia severity, timing, thrombosis or other sequelae, other causes of thrombocytopenia for the scenario you are assessing. Calculates the 4Ts pretest probability score for heparin-induced thrombocytopenia (HIT) based on thrombocytopenia severity and timing, thrombosis or other sequelae, and other causes of thrombocytopenia. Score 0–8; ≥4 warrants investigation. Use the hit 4ts score result to inform your calculation.

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Frequently Asked Questions