According to the British Thoracic Society, CTPA has a higher specificity for detecting pulmonary emboli, and is the preferred method of imaging over ventilation-perfusion isotope scans and pulmonary angiography. Although the latest generation of multi-slice scanners enable clinicians to correlate the severity of patient symptoms to the clot burden, subsegmental clots are more difficult to detect. Better techniques for image requisition and advanced CT technology allows for more accurate detection of peripheral pulmonary emboli (British Thoracic Society, 2003).

Most hospitals in Ireland have access to CTPA, and it is the preferred method of investigation because of its negative predictive value of 96-97% when used to detect PE. However, this also allows misuse of this imaging modality, potentially exposing patients to unnecessary radiation.

The (NICE guideline, 2023) for venous thromboembolic disease have recommended that the PERC rule should be applied to patients who have been assessed and deemed to be low-risk of having PE.

However (NICE guideline, 2023) also advise to apply the 2-level Well’s criteria to patients who are suspected of having PE.  If patients score 4 or above on the Well’s score (PE likely), it is advised for them to be immediately offered CTPA. If patients score 4 or below (PE unlikely), it is advised to obtain a D-dimer within 4 hours. If a D-dimer cannot be obtained within 4 hours, it is recommended to anticoagulate the patient whilst awaiting the D-dimer.

The computerised ordering system for imaging in our hospital, NIMIS, requires the Well’s score and D-dimer, as well as urgent scans that was discussed with a radiologist, to be recorded in a mandatory questionnaire prior to completing the order for CTPA. This ensures that each clinician ordering a CTPA is aware of, and is compliant with current guidelines for CTPA.

This re-audit will review all reported CTPA’s in our hospital from January 2023 – March 2023. Data from July-September 2017 will be compared to assess if clinicians ordering CTPA have improved practice, and if compliance with recommendations from current guidelines has improved since 2017.