[Age-adjusted D-dimer cut-offs to diagnose thromboembolic events: validation in an emergency department]

Abstract

Background: In elderly patients, an unspecific increase of fibrin degradation products in blood is observed. Thus, the D-dimer test to rule out thromboembolic events has a high false-positive rate in elderly patients. Our aim was to validate an age-adjusted D-dimer cut-off and to assess its utility in elderly patients.

Methods: In a retrospective cohort of outpatients (n = 1033) presenting to our emergency department with suspected acute pulmonary embolism and/or deep vein thrombosis (PE/DVT), age-adjusted D-dimer cut-off values were derived using receiver operating characteristic (ROC) curve analysis. Subsequently, the proportion of patients with normal D-dimer and false-negative test results, respectively, and the number needed-to-test (NNT) were compared for conventional and age-adjusted cut-off values.

Results: Using the conventional cut-off of 0.5 mg/dl, PE/DVT could be excluded in 68 % of patients, whereas the age-adjusted cut-off [(age × 0.016) mg/l] ruled out 77 % of patients. Particularly in patients > 70 years, the negative prediction accuracy of excluding a PE/DVT increased explicitly. The failure rate of the age-adjusted cut-off value was 0.8 % (95 % confidence interval 0.3-1.6 %).

Conclusion: The age-adjusted D-dimer cut-off point increases the proportion of older patients, in whom an acute thromboembolic event can be excluded.