Comparison of Screening Scores for Heparin- Induced Thrombocytopenia After Cardiopulmonary Bypass

Objectives: To compare screening scores for heparin-induced thrombocytopenia (HIT) after cardiopulmonary bypass (CPB).

Design: Retrospective cohort study.

Setting: Cardiothoracic surgery units within a large tertiary healthcare facility from September 2010 to January 2020.

Participants: All adult patients tested for heparin-induced platelet antibody (HIPA) within 2 weeks after surgery requiring CPB.

Interventions: Using data available to providers at the time HIPA were checked, the 4T's Score, a modified 4T's Score, and a score proposed by Lillo-Le Louet (LLL) et al. were calculated. A retrospective chart review was performed for each patient to determine actual presence of HIT, and screening scores were compared for accuracy.

Measurements and main results: Criteria for inclusion were met in 266 patients. Of these, 34 (12.8%) were high likelihood of HIT, 16 (6.0%), additional patients were clinically ambiguous, and 216 (81.2%) were high likelihood of alternative cause for thrombocytopenia. HIPA tests done before postoperative day 5 were not associated with any high-likelihood cases of HIT regardless of preoperative heparin exposure. Although traditional 4T's ≥4, modified 4T's ≥3, and LLL ≥2 had statistically similar sensitivity for predicting HIT, the modified 4T's and LLL had superior specificity (p < 0.001).

Conclusions: Appropriate screening for HIT curbed inappropriate HIPA testing, and reduced the need for empirical treatment while awaiting confirmatory test results. Traditional 4T's was statistically inferior to both the LLL score and a modified version of the 4T's to screen for HIT within 2 weeks of CPB.