Safety of D-dimer testing as a stand-alone test for the exclusion of deep vein thrombosis as compared with other strategies

Background: Several strategies for safely excluding deep vein thrombosis (DVT) while limiting the number of imaging tests have been explored. Objectives: To determine whether D-dimer testing could safely and efficiently exclude DVT as a stand-alone test, and evalu- ate its performance as compared with strategies that incorporate the Wells score and age-adjusted D-dimer. Patients/Methods: We included consecutive outpatients referred with suspected DVT to the Emergency Depart- ment at Østfold Hospital, Norway. STA-Liatest D-Di PLUS D-dimer was analyzed for all patients. Patients with a D-dimer level of ≥ 0.5 lgmL 1 were referred for compression ultrasonography (CUS). In patients with a D-dimer level of < 0.5 lgmL 1 , no further testing was performed and anticoagulation was withheld. Patients were followed for 3 months for venous thromboembolism (VTE). Results: Of the 913 included patients, 298 (33%) had a negative D-dimer result. One hundred and seventy- three patients (18.9%) were diagnosed with DVT at baseline. One of 298 patients had DVT despite having a negative D-dimer result, resulting in a failure rate of 0.3% (95% confidence interval [CI] 0.1–1.9%). Adding the modified Wells score would have yielded a failure rate of 0.0% (95% CI 0.0–1.8%) while necessitating 87 more CUS examinations. Age-adjusted D-dimer as a stand- alone test would have necessitated 80 fewer CUS exami- nations than fixed D-dimer as a stand-alone test, at the cost of a failure rate of 1.6% (95% CI 0.7– 3.4%). Con- clusions: This outcome study shows that a negative high-sensitivity D-dimer result safely excludes DVT in an outpatient population, and necessitates fewer CUS than if used in combination with Wells score. The safety of stand-alone age-adjusted D-dimer needs further assess- ment in prospective outcome studies