Beyond the clot: diagnostic yield, biomarker performance, and the landscape of alternative diagnoses in emergency CT pulmonary angiography

BACKGROUND: Computed Tomography Pulmonary Angiography (CTPA) is the gold standard for diagnosing acute Pulmonary Embolism (PE). However, overlapping symptoms and reliance on non-specific biomarkers often lead to over-testing. This study provides a comprehensive analysis of CTPA utilization, evaluating diagnostic yield, biomarker performance, and the landscape of alternative thoracic diagnoses with a special focus on radioprotection. METHODS: A retrospective, single-centre study of 659 patients evaluated in the Emergency Department (ED) between January 2023 and November 2025. Data were extensively stratified by patient age, presenting symptoms, D-dimer thresholds, and radiological outcomes. RESULTS: The global diagnostic yield was 20.9% (138/659). Advanced age correlated linearly with PE prevalence (25.2% in patients > 70 years) but inversely with D-dimer specificity, resulting in a 42% false-positive biomarker rate in the geriatric cohort. Dyspnea was the most common presenting symptom (62%) but demonstrated limited diagnostic specificity for PE. Crucially, in the 521 PE-negative scans, CTPA provided clinically relevant alternative diagnoses in 72.0% of cases (375/521), primarily infectious consolidations and heart failure. CONCLUSION: While clinical triage remains within optimal international benchmarks, the standard diagnostic algorithm is heavily confounded by patient age and inflammatory "PE mimics." Integrating age-adjusted D-dimer thresholds and structured pre-test probability scoring is imperative to optimize resource allocation and mitigate unnecessary radiation exposure while preserving diagnostic safety (Righini in JAMA 311:1117-1124, 2014;Konstantinides in Eur Heart J 41:543-603, 2020;).