Age-adjusted D-dimer thresholds safely ruled out pulmonary embolism in patients aged ≥50 years with a 3.4% failure rate, potentially avoiding 17.4% of unnecessary CTPA scans.
Cohort (n=1,135)
Yes
Does the use of age-adjusted D-dimer thresholds safely reduce the need for CTPA in patients aged ≥50 years with suspected pulmonary embolism?
Retrospective application of age-adjusted D-dimer thresholds in patients ≥50 years with suspected pulmonary embolism demonstrated high sensitivity and could safely reduce CTPA utilization by 17.4%, despite a slightly elevated failure rate for low-burden emboli.
Absolute Event Rate: 3.4% vs 0%
Aims This study aims to assess the safety of age-adjusted D-dimer thresholds (AAT) and their impact on imaging utilisation for pulmonary embolism (PE) rule-out in settings where AAT are not routinely applied. Methods and materials We retrospectively studied patients aged ≥50 years who underwent D-dimer testing (without age adjustment) and computed tomography pulmonary angiogram (CTPA) for suspected PE at two different hospital sites (January 2022 to December 2023). Pre-test probability was recorded using the two-level Wells' score. Age-adjusted thresholds were retrospectively calculated, and sensitivity, specificity, negative predictive value (NPV), and failure rate were determined. False negatives were reviewed in further detail. Results Among 1,135 patients, PE was confirmed in 183 (16.1%). Age-adjusted D-dimer yielded 176 true positives, 7 false negatives, 755 false positives and 197 false negatives. Sensitivity was 96.2%, specificity 20.7% and NPV 96.6%. The failure rate among D-dimer negative patients was 3.4% (95% CI: 1.7-6.8%). False negatives included two subsegmental, three segmental with and without subsegmental elements, two lobar and one chronic embolus; none had right ventricular strain. Implementation of AAT could have avoided 197 CTPAs (17.4%), thereby reducing the imaging department's workload and unnecessary contrast and radiation administration. Conclusion In routine National Health Service (NHS) practice, age-adjusted D-dimer demonstrates high sensitivity and NPV in patients ≥50 years. The 3.4% failure rate was above the 3% benchmark, though all missed emboli were of low clot burden without right ventricular strain. These findings support integrating age-adjusted D-dimer into structured pathways to safely reduce CTPA use and resource burden.
Kelsh et al. (Sun,) conducted a cohort in Suspected pulmonary embolism (n=1,135). Age-adjusted D-dimer threshold (AAT) vs. Standard D-dimer threshold (<250 µg/L) was evaluated on False negative rate (failure rate) (95% CI 1.7-6.8). Age-adjusted D-dimer thresholds safely ruled out pulmonary embolism in patients aged ≥50 years with a 3.4% failure rate, potentially avoiding 17.4% of unnecessary CTPA scans.