Performance of the age-adjusted cut-off for D-dimer in patients with cancer and suspected pulmonary embolism.

Background: Cancer patients frequently present with suspected pulmonary embolism (PE). The D-dimer (DD) test is less useful in excluding PE in cancer patients due to the lower specificity. In the general population, the age-adjusted cutoff for DD combined with a clinical decision rule (CDR) improved specificity in the diagnosis of PE.

Objective: To evaluate the safety and efficacy of the age-adjusted cutoff (defined as age∗10μg/L in patients >50years) combined with a CDR for the exclusion of PE in cancer patients.

Methods: We conducted a prospective study to evaluate the age-adjusted cutoff in patients with suspected PE. Here we report a post-hoc analysis on the performance of the age-adjusted cutoff in patients with and without cancer. The primary outcome was the rate of venous thromboembolic events (VTE) during three-month follow-up.

Results: Of 3324 patients with suspected PE, 429 (12.9%) patients had cancer. The prevalence of PE was 25.2% in cancer patients and 18% in patients without cancer (p<0.001). Among cancer patients with an unlikely CDR, 9.9% had a DD <500μg/L as compared with 19.7% using the age-adjusted cutoff. In patients without cancer, these rates were 30.1% and 41.9%. The proportion of cancer patients in whom PE could be excluded by CDR and DD doubled from 6.3% to 12.6%. No VTE occurred during three-month follow-up (failure rate 0.0% (95% CI 0.0-6.9%)).

Conclusions: Compared with the conventional cutoff, the age-adjusted D-dimer cutoff doubles the proportion of patients with cancer in whom PE can be safely excluded by CDR and DD without imaging.