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

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. 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. 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. 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. In this prospective cohort of ambulatory cancer patients with clinically suspected DVT, the CPTP-adjusted 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. •Optimal D-dimer threshold to withhold imaging for DVT is unclear in cancer patients.•239 cancer outpatients with suspected DVT were prospectively enrolled.•Age-, CPTP-adjusted and standard D-dimer approaches were compared.•CPTP-adjusted D-dimer strategy appeared to hold higher specificity and efficiency.•A simplified CPTP rule was derived from Wells rule, but requires adequate validation.