Assessing D-dimer test specificity for pulmonary embolism diagnosis in emergency departments.

Pulmonary Embolism (PE) is a potentially life-threatening condition that requires rapid and accurate diagnosis in emergency settings. Although Computed Tomography Pulmonary Angiography (CTPA) is the reference standard, its routine use is limited by cost, radiation exposure, and contrast-related risks. This study aimed to evaluate the diagnostic performance of D-dimer testing in patients suspected of PE. A retrospective cross-sectional study was conducted at King Khalid University Hospital, Riyadh, Saudi Arabia, including 1,316 patients who underwent D-dimer testing between January and December 2023. CTPA was used as the reference standard in patients selected for imaging based on clinical assessment. The prevalence of confirmed PE was 8.4%. D-dimer demonstrated high sensitivity (87.4%) and excellent negative predictive value (97.4%), supporting its role as a reliable rule-out tool. However, specificity was low (43.9%) and the positive predictive value was limited (12.5%), reflecting a high rate of false-positive results. Application of the age-adjusted D-dimer threshold reclassified 23 patients, resulting in a modest improvement in specificity from 43.9% to 45.8%, while maintaining diagnostic safety. Receiver operating characteristic analysis showed modest discriminative ability (AUC = 0.656). D-dimer levels were significantly associated with increasing age and male sex, while nationality showed no significant effect. In conclusion, D-dimer testing is an effective initial screening tool for excluding PE in emergency departments; however, its low specificity limits its standalone diagnostic value. Integration with clinical prediction rules and age-adjusted thresholds may improve diagnostic accuracy and reduce unnecessary imaging.