Original research
Figure 2 Stacked bar chart of numbers attending hospital per hour of day (stratified by prospective/retrospective recruitment).
interpreted with caution. AUROC for clinician likelihood was based on an ordinal score with wider range than for all the CDTs. The clinician likelihood also had a much higher propor- tion of missing data (26% compared with 4–7% in the other decision tools). Finally, the study taking place in the ED with ongoing recruitment of all-comers with potential AAS symp- toms may have biassed towards a higher accuracy of clinical gestalt and may have reduced the risk of ED clinicians missing AAS. Nevertheless, the finding that an ED clinician AAS like- lihood of 3/10 or greater detected all AAS cases, suggests that ED clinician gestalt could be a useful addition to any AAS CDT. Currently only the Canadian clinical practice guideline includes any measure of ED clinician gestalt, and this clinical decision tool performed well in our evaluation. In our study, around half of patients could not be recruited prospectively despite extensive advertisement, excellent site engage- ment and acceptance among the ED community that AAS is a top emergency medicine research priority. 26 27 Conducting research in this area is challenging. Some patients with AAS are missed because the diagnosis is not considered. These patients’ care will not be improved by prospective ED research studies as they will not be included. Our data is limited by the fact that it is not possible to capture patients with AAS where the diagnosis was not considered, who subsequently died without imaging or post-mortem. If a diag- nostic intervention is researched in those whom the ED clinician suspects AAS, this risks the Hawthorne effect. 28 This study has limitations. Retrospective recruitment of around half of patients led to missing clinician gestalt data. D-dimer and CT scans were only available if they were ordered by the treating clinician. Generating accurate test characteris- tics of decision tools was therefore difficult, especially around D-dimer estimation. Here, exclusion of unknown and missing values may have led to bias in the test characteristics. However, in our analyses we carefully considered the dependence of the
It may be that CTA rate was increased (407/5446; 7%) from that anticipated in the power calculation (125/5000; 2.5%) due to the presence of this study in the ED biasing ED clinicians to over investigate for AAS. However, this increased CTA rate may also reflect a more widespread generalised change in usual care towards more ED clinicians investigating potential AAS symptoms with CTA. This study shows the potential implica- tions of over-interpreting the recommendation that all patients presenting with potential AAS symptoms should undergo CTA. A literal interpretation could have led to 5008 further patients undergoing CT scan in our study. The Aortic Syndrome Evidence Synthesis (ASES) study, an evidence synthesis and value of infor- mation analysis is currently underway, determining what CT positivity rate would represent a cost-effective use of resources. 25 While clinician gestalt appears to perform well, a sensitivity of 45% when an ED clinician rates AAS as the most likely diag- nosis, suggests additional help to stratify who should undergo CT is required. While our low AAS prevalence means we must be cautious about comparing the performance of different clinical decision tools, the Sheffield score (sensitivity of 36%) is probably not suitable for clinical use, with too many missed AAS cases. The other clinical decision tools performed better, but alone did not reach sufficient sensitivity for clinical use in our cohort. Table 2 potentially explains the poor specificity of the CDTs. The ADD-RS and Canadian tools both include ‘Pain severe intensity or worst ever’ and ‘migrating or radiating pain’. These characteristics are present in 32% and 34% of people with potential AAS symptoms in our cohort, yet not all under- went CT. This suggests that clinicians are choosing not to CT all patients with these symptoms, and that CDTs need to better differentiate which patients with severe intensity, worst ever, migrating or radiating pain should undergo CT. While the AUROC for ED clinician AAS likelihood rating was impressive compared with individual CDTs, this must be
McLatchie R, et al . Emerg Med J 2024; 41 :136–144. doi:10.1136/emermed-2023-213266
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