A computed tomographic pulmonary angiography (CTPA) scan is the investigation of choice for most people in whom a pulmonary embolism (PE) is suspected (1). However, the signs and symptoms of a PE can be non-specific, and there are concerns that CTPA scans are being overused in the evaluation of patients with cardio-respiratory symptoms, with low diagnostic yield (2)

Standards

National guidelines produced by the National Institute of Care and Excellence (NICE) advise that a CTPA should only be requested if a Wells score for PE is greater than 4, or if there is a positive D-dimer result (1). 

If requested appropriately, The Royal College of Radiologists (RCR) has suggested that more than 15% of CTPAs should be positive for PE (3). 

The National Confidential Enquiry into Patient Outcome and Death (NCEPOD) for PE further advised that all CTPA reports should document the presence or absence of right heart strain if a CTPA is positive for PE, to allow adequate risk stratification (4).  

Local guidelines also require that all positive scans have a ‘PE alert’ added to the report to ensure appropriate haematology follow up. 

Methodology

The requests and reports of 500 consecutive CTPAs in Leeds Teaching Hospitals NHS Trust were reviewed in 2022.

Following the results of this audit, a mandatory electronic questionnaire was added to CTPA request forms that required all users to input a Wells score or D-dimer result when requesting a CTPA. A structured proforma for reporting CTPA scans was also introduced – this automatically entered a PE alert shortcode if a scan was positive and alsocontained a section on right heart strain.

The audit was then repeated in 2024 to assess the impact of these changes.

Conclusions

1. Ratnakumar R, Corcoran J, Talwar A, et al P50 Changing use of CT pulmonary angiography in a uk tertiary hospital over a 6-year period. Thorax 2016;71:A109-A110.

2. National Institute for Health and Care Excellence. Venous thromboembolic diseases: diagnosis, management and thrombophilia testing. 2020. Available from: https://www.nice.org.uk/guidance/ng158

3. National Confidential Enquiry into Patient Outcome and Death. Pulmonary Embolism: Know the Score. 2019. Available from: https://www.ncepod.org.uk/2019pe.html

4. Royal College of Radiologists. Appropriateness of usage of computed tomography pulmonary angiography (CTPA) investigation of suspected pulmonary embolism. 2021. Available from: https://www.rcr.ac.uk/audit/appropriateness-usage-computed-tomography-pulmonary-angiography-ctpa-investigation-suspected