Is stand-alone D-dimer testing safe to rule out acute pulmonary embolism?

Area of Science:

• Emergency Medicine
• Diagnostic Testing
• Cardiology

Background:

• A positivity threshold of 750 μg L^-1 for stand-alone D-dimer testing has been proposed to rule out acute pulmonary embolism (PE).
• This approach aims for safe and efficient PE diagnosis without additional imaging.
• Validation of this diagnostic strategy is necessary.

Purpose of the Study:

• To evaluate the safety and efficacy of stand-alone D-dimer testing at a 750 μg L^-1 threshold for ruling out PE.
• To determine the negative predictive value (NPV) of this threshold across diverse patient subgroups.

Main Methods:

• A post-hoc analysis of individual data from 7268 patients with suspected PE across six prospective studies.
• Patients were stratified using the Wells rule, followed by quantitative D-dimer testing for those with 'PE unlikely' scores.
• A meta-analytic approach assessed the NPV of D-dimer < 750 μg L^-1 overall and in risk subgroups.

Main Results:

• The pooled incidence of PE was 23%. Overall, 44% of patients had a D-dimer < 750 μg L^-1, with a 2.8% PE diagnosis rate (NPV 97.2%).
• The NPV was highest in low-probability PE patients (99.2%) and lowest in high-probability PE patients (79.3%).
• NPVs were also reported for patients with active cancer (96.2%), previous venous thromboembolism (94.7%), and inpatients (92.7%).

Conclusions:

• Stand-alone D-dimer testing at a 750 μg L^-1 threshold is not universally safe for ruling out acute PE.
• The NPV varies significantly across different patient risk profiles.
• Clinical decisions should consider patient-specific risk factors alongside D-dimer results.