J Thromb Haemost. 2021 Apr 19. doi: 10.1111/jth.15344. Online ahead of print.
BACKGROUND: Diagnosis of heparin-induced thrombocytopenia (HIT) requires pre-test probability assessment and dedicated laboratory assays.
OBJECTIVE: To develop a pre-test score for HIT.
DESIGN: Observational; analysis of prospectively collected data of hospitalized patients suspected with HIT (ClinicalTrials.gov NCT00748839).
SETTING: Thirty-one tertiary hospitals in France, Switzerland, and Belgium.
PATIENTS: Patients tested for HIT antibodies (2,280 evaluable), randomly allocated to derivation and validation cohorts.
MEASUREMENTS: Independent adjudicators diagnosed HIT based on the prospectively collected data and Serotonin Release Assay results.
RESULTS: HIT was diagnosed in 234 (14.7%) and 99 (14.5%) patients in the two cohorts. Eight features were associated with HIT (in brackets, points assigned for score calculation of the score): unfractionated heparin (1); therapeutic-dose heparin (1); cardiopulmonary bypass (cardiac surgery) (2); major trauma (3); 5- to 21-day interval from anticoagulation initiation to suspicion of HIT (4); ≥ 40% decrease in platelet count over ≤ six days (3); thrombotic event, arterial (3) or venous (3). The C-statistic was 0.79 [95% CI, 0.76-0.82]. In the validation cohort, the area under the receiver operating characteristic curve was 0.77 [95% CI, 0.74-0.80]. Three groups of scores were defined; HIT prevalence reached almost 30% in the high-probability group.
LIMITATION: The performance of the score may depend on settings and practices.
CONCLUSION: The objective, easy-to-collect, clinical features of HIT we evidenced were incorporated into a pre-test score, which may guide clinical decisions regarding diagnostic testing and anticoagulation.