Age- versus clinical pretest probability-adjusted D-dimer to rule out lower-extremity deep vein thrombosis in ambulatory patients with active cancer

Background: In patients with suspected deep vein thrombosis (DVT), D-dimer thresholds adjusted to age or clinical pretest probability (CPTP) increase the proportion of patients in whom DVT can be safely excluded compared to a standard approach using a fixed D-dimer threshold. Performance of these diagnostic strategies among cancer patients is uncertain.Aim: To compare the performance of age- and CPTP-adjusted D-dimer approaches among cancer outpatients with clinically suspected DVT, and derive a cancer-specific CPTP rule. Patients and methods: Consecutive ambulatory patients with active cancer and clinically suspected DVT of the lower extremity underwent CPTP assessment using the Wells rule, D-dimer testing, and whole-leg compression ultrasonography. Patients with normal ultrasonography were followed-up for 3 months for the occurrence of symptomatic venous thromboembolism.Results: Upon referral, DVT was diagnosed in 48 of 239 (20.1 %) patients. The age-adjusted approach showed higher specificity and efficiency than the standard approach. Compared to the standard and age-adjusted strategies, the CPTP-adjusted approach had 35 % and 21 % higher specificity, and 34 % and 21 % higher efficiency, respectively. Failure rate, sensitivity, and predictive values were similar across strategies. A simplified CPTP score derived from the Wells rule reduced unnecessary imaging with similar accuracy and efficiency, but higher failure rate.Conclusions: In this prospective cohort of ambulatory cancer patients with clinically suspected DVT, the CPTPadjusted D-dimer approach held the highest specificity and efficiency, potentially safely reducing unnecessary ultrasonography examinations compared to other approaches. Additional studies are warranted to evaluate the use of a simplified clinical prediction rule in this setting.