Selective D-Dimer Testing for Diagnosis of a First Suspected Episode of Deep Venous Thrombosis

Background: D-Dimer testing is sensitive but not specific for diag-nosing deep venous thrombosis (DVT). Changing the use of testing and the threshold level for a positive test result on the basis of risk for DVT might improve the tradeoff between sensitivity and spec-ificity and reduce the need for testing. Objective: To determine whether using a selective D-dimer testing strategy based on clinical pretest probability (C-PTP) for DVT is safe and reduces diagnostic testing compared with using a single D-dimer threshold for all patients. Design: Randomized, multicenter, controlled trial. Patients were allocated using a central automated system. Ultrasonographers and study adjudicators but not other study personnel were blinded to trial allocation. (ClinicalTrials.gov: NCT00157677) Setting: 5 Canadian hospitals. Patients: Consecutive symptomatic patients with a first episode o