Clinical Utility and Outcomes of Repeat Computed Tomography Pulmonary Angiography in Suspected Pulmonary Embolism: A Retrospective Cohort Study.

BACKGROUND

Pulmonary embolism (PE) remains a significant cause of morbidity and mortality. While computed tomography pulmonary angiography (CTPA) is the diagnostic gold standard, uncertainty persists in some patients after a negative or inconclusive scan. The role of repeat CTPA and the utility of D-dimer testing in this context are not well defined.

OBJECTIVES

The objectives of this study are to evaluate the prevalence and severity of PE detected on repeat CTPA, assess the diagnostic performance of D-dimer testing in repeat evaluations, and examine the clinical outcomes and resource implications associated with repeat imaging.

METHODS

This retrospective cohort study was conducted across public tertiary care hospitals in Eastern Province, Saudi Arabia, from January 2022 to December 2023. Adult patients (≥18 years) presenting to the emergency department with suspected PE who underwent initial CTPA and had a repeat visit within 30 days were included. Patients undergoing repeat CTPA comprised the primary analysis group. Data included demographics, clinical risk factors, D-dimer levels, CTPA findings, and outcomes. Diagnostic accuracy metrics were calculated for D-dimer. Statistical analyses compared patients with and without repeat imaging.

RESULTS

Out of 412 patients evaluated for suspected PE, 61 (14.8%) underwent repeat CTPA. These patients were older and more likely to have cancer, a history of venous thromboembolism (VTE), and elevated Wells scores. PE was detected in 34.4% (n=21) of the repeat scans compared to 14.3% (n=59) of the initial scans (P < 0.001). Repeat imaging showed more frequent right ventricular strain (14.8%; n=9) and incidental findings (18.0%; n=11). D-dimer testing remained highly sensitive (>95%) but had low specificity; however, its positive predictive value increased during repeat visits (38.2% (21 of 55) vs. 19.3% (57 of 295)). Repeat CTPA was associated with higher hospital admission rates (55.7% (n=34) vs. 16.8% (n=59), P < 0.001) and ICU admission rates (9.8% (n=6) vs. 1.4% (n=5), P = 0.002), more frequent contrast-related adverse events (6.6% (n=4 ) vs. 1.1% (n=4), P = 0.017), and significant changes in clinical management (42.6%; n=26).

CONCLUSIONS

Repeat CTPA identifies a meaningful proportion of missed or newly developed PEs, particularly in high-risk patients. However, its benefits must be weighed against increased adverse events and healthcare resource use. Improved risk stratification and more targeted use of D-dimer testing could help optimize repeat imaging decisions and reduce unnecessary scans.