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

Essentials The aim of deep vein thrombosis (DVT) diagnostic work-up is to maximize both safety and efficiency. We explored whether D-dimer is safe and efficient as a stand-alone test to exclude DVT. Our findings suggest it is a safe, efficient and simplified diagnostic strategy. The safety of age-adjusted D-dimer as a stand-alone test requires further investigation. SUMMARY: 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 evaluate 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 Department 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 μg mL-1 were referred for compression ultrasonography (CUS). In patients with a D-dimer level of < 0.5 μg mL-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 examinations 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%). Conclusions 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 assessment in prospective outcome studies.