Evolution of CT pulmonary angiography: referral patterns and diagnostic yield in 2009 compared with 2006

CT pulmonary angiography (CTPA) is an increasingly popular imaging test for assessing patients with acute chest pain.

To evaluate the number of CTPA performed in 2009 compared with 2006 and assess the frequency of pulmonary embolus (PE) versus alternative diagnoses.

Numbers of CTPA and V/Q scans performed in a six-month period of 2006 and 2009 were established by review of the hospital radiology information system. CTPAs were evaluated by two radiologists in consensus and the incidence of pulmonary embolism and alternative diagnoses in 2006 and 2009 were recorded.

The final study groups were 99 patients who underwent CTPA in 2006 and 149 patients in 2009. There was a significant fall in the incidence of PE identified on CTPA in 2009 compared to 2006 (11% versus 21%, P = 0.04). There was a non-significant rise in the incidence of alternative diagnoses in 2009 compared to 2006 (45% versus 40%, P = 0.48). Nine types of alternative radiological diagnoses were made on CTPA, the most common of which was pneumonia in both time periods (17% and 12%). Eighty-seven V/Q scans were performed in the study period in 2006, compared to 109 in 2009. The incidence of PE identified on V/Q scanning remained stable (8% in 2009 versus 12% in 2006, P = 0.44).

The numbers of CTPAs being performed has increased in three years. The incidence of PE identified has fallen and there has been a modest increase in the number of alternative diagnoses.