Age-adjusted d-dimer cut-off levels increase the clinical utility of ruling out pulmonary embolism in elderly patients

Background: The D-Dimer (DD) test, used to rule out pulmonary embolism (PE), is less useful in elderly patients due to a lower specificity. We retrospectively derived and validated the efficacy of an age- dependent DD cut-off combined with clinical probability for the exclusion of PE in four large management studies. Methods: The derivation set consisted of consecutive outpatients > 50 years with suspected PE. The DD cut-off was based on ROC-curve analyses. The proportion of patients with a normal DD test and the false negative rates were calculated. The age-adjusted DD cut-off was then validated in patients > 50 years with an unlikely Wells score (> 4) or a non-high Revised Geneva Score (> 10) from two independent cohorts of consecutive patients, respectively. The Vidas DD test was used in all cohorts (combined with Tinaquant in validation set 1). Results: The new DD cut-off was defined as patient's age x 10 μg/L. Using the new cut-off PE could be excluded in a higher number of patients > 50 years (Table). Among patients > 70 years, the increase in the proportion of patients with a DD below the new cut-off compared to the old cut-off was 2.3-fold in the derivation set, 2.0-fold in validation set 1 and 2.2-fold in validation set 2, respectively. [Table represented ]Conclusion: An age-adjusted cut-off of the D-dimer combined with clinical probability greatly increases the proportion of elderly patients in whom PE can be safely excluded. Disclosure of interest: none declared