Clinical decision rule and D-dimer have lower clinical utility to exclude pulmonary embolism in cancer patients Explanations and potential ameliorations

Patients with malignancy frequently present with clinically suspected pulmonary embolism (PE). However, the safe and efficient combination of a clinical decision rule (CDR) and D-dimer test to rule out PE performs less well in patients with malignancy. We examined potential explanations and analysed whether elevating the D-dimer cut-off could improve the clinical utility. We used data on consecutive patients with suspected PE included in a multicenter management study. The performance of the Wells CDR and the D-dimer test was compared between patients with and without malignancy and multivariable analysis was used to compare the weights of the CDR variables. Furthermore, we combined the CDR (cut-off <= 4) with different D-dimer cut-off levels for the exclusion of PE. Of 3,306 patients with suspected PE, 475 (14%) had cancer. The Wells rule variables were less diagnostic in cancer patients. Increasing the D-dimer cut-off level to 700 mu g/l for all ages or using an age-dependent cut-off resulted in an increase in the proportion of patients in whom PE could be excluded from 8.4% to 13% and 12%, respectively. The corresponding false-negative rates were 1.6% (95% confidence interval 0.3-8.7%) and 0.0% (0.0-6.3%). The Wells CDR and D-dimer perform less well in patients with suspected PE if they have cancer. Individual variables in the Wells rule are less diagnostic in cancer patients than in non-cancer patients with suspected PE. A CDR combined with an age-dependent D-dimer cut-off shows a modest improvement of the strategy in cancer patients.