027 RESPECTED-long, a single centre follow up of ED CTPA use over a decade and effect on diagnostic yield

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Objectives Emergency Department (ED) use of CT-pulmonary angiography (CTPA) to diagnose Pulmonary embolism (PE), had increased rapidly since 2000.There are serious concerns increased use is mainly from over-use, with likely increased false positives and unnecessary testing. ED-CTPA was highlighted in Australian choosing -wisely guidelines. In this unit anecdotal evidence suggested major increased CTPA-use after Covid. There were two linked aims/hypotheses. 1) That ED CTPA ordering was increasing at rates much above ED attendances and 2) if CTPA rates were significantly higher that this would be associated with decreasing yield from test overuse. For hypothesis1 a secondary review was to see if increased use was Covid related or a long-term trend. For hypothesis2 we explored if increased use was associated with increased diagnosis of smaller PE (subsegmental or isolated segmental PE). Method For hypothesis one we extracted imaging data which identified monthly ED-CTPA numbers over a decade (2014–2023) to compare with our previous study (Ref1). Data was extracted de-identified. We presumed that increasing rates would dilute yield proportionately. We looked at VQ ordering levels over the same period. For hypothesis 2 we examined yield from July 2023 onwards. A power calculation was perfomed based on the expected dilutional effect of increasing CTPA rates. We extracted data using the same methodology/database as the RESPECTED study. Data was patient demographics; if a PE was seen/excluded; the highest-level vessel if PE seen; if concerns re degraded image quality . Analysis: difference in proportions/rates vs RESPECTED (2013–14 data) for hypothesis one. For hypothesis 2 difference in yield 2023 vs. 2012–13. We prospectively looked at proportions of highest vessel involved. We performed post-hoc analysis of sex/age interactions for yield. Inter-rater reliability was analysed. Results Hypothesis1) ED- CTPA increased from 480 p.a. to1050 in 2023. Attendances increased from 63, 000 to 74000. ED-CTPA rates increased from 8.2/1000 attendances (2012–13) to 13.6/1000 in 2023, (p < 0.0001). There were flattening increases during 2020 and 2022 (Covid associated reduced ED attendances) but CTPA rates increased to trend in following years. VQ rates dropped significantly, but by < 1/1000. Hypothesis 2) ED-CTPA yield (positive PE rates) were unaltered (16.3% 2012–13 vs 15.7% 2023–24). Large PE (lobar or larger) were seen less frequently, and intermediate size PE more frequently) but small PE rates did not change signficantly. Numbers of PE diagnosed increased significantly as PE/1000 attendances (1.4 vs 2.1/1000). Patients having CTPA were older than the overall ED cohort but not more female. Females had statistically lower yield than men overall. Young women had a yield of only 3%. All age/sex cohorts over age 40 had yields above 15% Conclusions ED-CTPA rates increased markedly (>50%) over 2014–2023. Surprisingly this had no significant effect on yield, with a 50% increase on rates of PE diagnosed. Overall PE seen on CTPA were smaller (more intermediate size) but smallest PE increase insignificantly, suggesting false positives aren’t driving increased PE. The increased use of CTPA is within the rates seen in 2012–14 in the RESPECTED study, but our PE rate is higher than any reported then. ED-CTPA usage is low compared with USA and yield high. Similar findings have been reported from other countries, with increasing CTPA use, PE diagnosis and more intermediate PE. IT is unclear why PE rates should be increasing but EDs are seeing more acute patients, and comorbidity, age and obesity in the general population could be driving increased PE rates. Future studies should look to see if this is seen throughout our region and look at yield before Covid.

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