PB1021 - Using an age and fibrinogen levels adjusted D-dimer cutoff significantly improves the specificity of D-dimer testing for excluding pulmonary embolism

Background: D-dimer testing play a key role for excluding pulmonary embolism (PE) in patients admitted to the emergency department who have a low pre-test probability of PE. In patients older than 50 years, the conventional fixed cutoff of 0.5 μg/mL fibrinogen equivalent units (FEU) has been progressively replaced by an age-adjusted cutoff, which significantly improves D-dimer specificity for excluding PE.

Aims: To assess whether using an optimized D-dimer cutoff, based on both age and fibrinogen levels, improves the specificity of D-dimer for excluding PE.

Methods: All patients admitted to the Emergency Department of the Brest University Hospital with suspected PE and a low pre-test probability of PE for whom a D-dimer testing was required were eligible for this prospective study (NCT03972839). D-dimer testing was performed using the STA®-Liatest® D-Di Plus (Stago, Asnières, France). Sensitivity, specificity and negative predictive value (NPV) of D-dimer for excluding PE according to conventional fixed or age-adjusted or age and fibrinogen levels adjusted D-dimer cutoffs were compared using receiver operating characteristics curve analysis.

Results: 2, 530 patients were included. PE was objectively confirmed in 91 (3.6%) patients. Using a fixed cutoff of 0.5 µg/mL FEU, the sensitivity of D-Dimer testing for excluding PE was 98.9% (95% CI 94.0-100.0%), its sensitivity was 57.1 (95%CI 55.1-59.1%) and its NPV was 99.9% (95% CI 99.6-100%). When using an age-adjusted cutoff, the sensitivity of D-dimer testing for excluding PE was 95.6% (95% CI 89.2-98.3%), its sensitivity was 65.1% (95%CI 63.2-66.9%) and its NPV was 99.7% (95%CI 99.4-99.9%). Finally, using a doubly adjusted cutoff based on age and fibrinogen levels, significantly improved D-dimer specificity (76%, 95% CI 74.3-77.7%) and NPV (100%, 95% CI 99.8-100%) for excluding PE without decreasing its sensitivity (100%, 95% CI 96.0-100).

Conclusion(s): Adopting an optimized age and fibrinogen levels adjusted D-Dimer cutoff significantly improves the specificity of D-dimer testing for excluding PE.