Heparin‐induced thrombocytopenia: Construction of a pretest diagnostic score derived from the analysis of a prospective multinational database, with internal validation

International audience; Background Diagnosis of heparin-induced thrombocytopenia (HIT) requires pretest probability assessment and dedicated laboratory assays.Objective To develop a pretest 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 (2280 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 Heparin-induced thrombocytopenia 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