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

The usefulness of the Wells score has not been assessed in hospitalized patients receiving prophylactic heparin.

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.

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.

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.