hit_4ts: 4Ts Score for Heparin-Induced Thrombocytopenia (HIT)

In cliot: Clinical Indices and Outcomes Tools

4Ts Score for Heparin-Induced Thrombocytopenia (HIT)

Description

Calculates the 4Ts Score to estimate the pretest probability of Heparin-Induced Thrombocytopenia (HIT). The score ranges from 0 to 8 and categorizes patients into Low, Intermediate, or High probability groups.

Usage

hit_4ts(thrombocytopenia_score, timing_score, thrombosis_score, other_causes_score)

Arguments

thrombocytopenia_score	Numeric (0, 1, or 2). Points for magnitude of platelet fall. 2: Fall >50% AND nadir >= 20. 1: Fall 30-50% OR nadir 10-19. 0: Fall <30% OR nadir < 10.
timing_score	Numeric (0, 1, or 2). Points for timing of platelet fall relative to heparin exposure. 2: Days 5-10 OR <=1 day (if prior exposure within 30 days). 1: >10 days OR unclear onset OR <=1 day (if prior exposure 30-100 days ago). 0: <4 days without recent exposure.
thrombosis_score	Numeric (0, 1, or 2). Points for thrombosis or other sequelae. 2: New confirmed thrombosis, skin necrosis, or acute systemic reaction. 1: Progressive/recurrent thrombosis, non-necrotizing skin lesions, or suspected thrombosis. 0: None.
other_causes_score	Numeric (0, 1, or 2). Points for likelihood of other causes for thrombocytopenia. 2: None apparent. 1: Possible. 0: Definite.

Value

A list containing:

Total_Score	Sum of the 4 components (Range 0-8).
Pretest_Probability	Risk category (Low, Intermediate, High) with estimated probability.
Interpretation	Clinical likelihood of HIT.
Management_Guidance	Suggested clinical actions based on risk.

References

Lo GK, et al. Evaluation of pretest clinical score (4 T's) for the diagnosis of heparin-induced thrombocytopenia in two clinical settings. J Thromb Haemost. 2006;4(4):759-65. doi:10.1111/j.1538-7836.2006.01787.x

Examples

# Example 1: High Probability
# >50% drop (2), Days 5-10 (2), New Thrombosis (2), No other causes (2)
hit_4ts(2, 2, 2, 2)

# Example 2: Low Probability
# <30% drop (0), Unclear timing (1), No thrombosis (0), Definite other cause (0)
hit_4ts(0, 1, 0, 0)

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