A prospective audit of requests for CT Pulmonary Angiography in haemodynamically stable non-pregnant patients with suspected Pulmonary Embolism

Abstract

Introduction: Pulmonary embolism (PE) is a common and occasionally fatal disease, therefore investigation must be targeted and accurate. Unnecessary investigation presents an increased risk of harm to the patient. On occasion, CT Pulmonary Angiography (CTPA) is not requested according to established guidelines.

Aim: This study aimed to address the criteria by which CTPAs were being requested.  Approval was obtained from data protection and ethics committees. Anonymous data was collected from hospital software and patients' case notes between Aug-Sept 2017.

Methods: 106 patients were recruited. Hospital notes were examined for demographics, reason for presentation, documentation of pre-test probability (PTP) testing, arterial blood gases (ABGs), electrocardiogram (ECG), indication for CTPA, and any complications. Hospital software provided data on blood investigations including D-dimer, CXR, time of CTPA order, and department and grade of doctor ordering CTPA.

Results: Dyspnoea, followed by a raised D-dimer, was the most common trigger for ordering CTPA (45.3%). A large majority (60.4%) of patients undergoing CTPA did not have ABGs taken. One fifth (21.7%) of CTPAs were positive. A PTP score was only documented in 10.4% of patients and was equally divided between Wells and Geneva scores. The Wells score was retrospectively calculated, with only 9.4% having a score >4 indicating likely PE. 1 patient had anaphylaxis to contrast and 5 developed contrast-induced nephropathy.

Conclusions: A basis for requesting a CTPA needs to be established, utilising the well-validated Wells Score, and D-dimer where indicated. A suspicion of PE should trigger a request for an ABG. CTPA is not without morbidity, and therefore should only be requested according to evidence-base.