Anum Saad, Hannah Raye, David Manners
This retrospective evaluation examined the theoretical impact of alternative D-dimer thresholds (age-adjusted and 1000 µg/L) in patients aged ≥ 50 years who underwent computed tomography pulmonary angiography (CTPA) after D-dimer testing. Among 291 patients with positive D-dimer and subsequent CTPA, the age-adjusted threshold maintained 100% observed sensitivity (95% CI 89.7%-100%), while the 1000-µg/L threshold missed three pulmonary emboli (sensitivity 91.2%, 95% CI 76.3%-98.1%). Applying these thresholds would have reduced CTPA use by 21.7% and 46.7%, respectively. These findings suggest that age-adjusted D-dimer thresholds may improve diagnostic efficiency in selected older patients; however, the absence of prospectively recorded pretest probability, verification bias and a lack of follow-up prevents conclusions about clinical safety.