The modified wells score accurately excludes pulmonary embolus in hospitalized patients receiving heparin prophylaxis

BACKGROUND: The usefulness of the Wells score has not been assessed in hospitalized patients receiving prophylactic heparin. METHODS: Retrospective, observational study of hospitalized patients receiving prophylactic heparin who underwent contrast-enhanced chest computed tomography (CT) for a concern of pulmonary embolism (PE) more than 2 days after admission. Patients with contraindications to, or interruptions in, prophylactic heparin were excluded. The modified (eg, dichotomous) Wells score was retrospectively calculated by reviewing each patient's record. Requesting a D-dimer was taken to mean that alternate diagnoses were of equal or greater likelihood than acute PE. RESULTS: From January 2006 through December 2007, 286 patients met inclusion criteria. Pulmonary embolus diagnosed by CT was present in 20 patients (7%). The sensitivity, specificity, positive and negative predictive values of a Wells score ≥4.0 were 95%, 27%, 9% and 99%, respectively. A D-dimer was ordered in 70 of the 74 PE-unlikely cases, was elevated in 67, and falsely positive in all but 1. CONCLUSIONS: The prevalence of PE in hospitalized patients receiving prophylactic heparin is lower than in cohorts from which the Wells prediction criteria were derived and validated. A modified Wells score <4 safely excludes PE in such patients and reduces the need for CT. D-dimer testing adds nothing to the evaluation.