Factors Predicting Misidentification of Acute Ischemic Stroke and Large Vessel Occlusion by Paramedics

Abstract

The emergence of thrombectomy for large vessel occlusions has increased the importance of accurate prehospital identification and triage of acute ischemic stroke (AIS). Despite available clinical scores, prehospital identification is suboptimal. Our objective was to improve the sensitivity of prehospital AIS identification by combining dispatch information with paramedic impression. We performed a retrospective cohort review of emergency medical services and hospital records of all patients for whom a stroke alert was activated in 1 urban, academic emergency department from January 1, 2018, to December 31, 2019. Using admission diagnosis of acute stroke as outcome, we calculated the sensitivity and specificity of dispatch and paramedic impression in identifying AIS and large vessel occlusion. We identified factors that, when included together, would improve the sensitivity of prehospital AIS identification. Two-hundred twenty-six stroke alerts were activated by emergency department physicians after transport by Indianapolis emergency medical services. Forty-four percent (99/226) were female, median age was 58 years (interquartile range, 50–67 years), and median National Institutes of Health Stroke Scale was 6 (interquartile range, 2–12). Paramedics demonstrated superior sensitivity (59% vs. 48%) but inferior specificity (56% vs. 73%) for detection of stroke as compared with dispatch. A strategy incorporating dispatch code of stroke, or paramedic impression of altered mental status or weakness in addition to stroke, would be 84% sensitive and 27% specific for identification of stroke. To optimize rapid and sensitive stroke detection, prehospital systems should consider inclusion of patients with dispatch code of stroke and provider impression of altered mental status or generalized weakness.

Emergency Medical Services dispatcher recognition of stroke: A systematic review

“…Of the included papers, 11 were from USA 9,15–24 , three from United Kingdom 25–27 , two from Australia 28,29 , two from Sweden 30,31 , one from Denmark, 32 one from France, 10 one from Iran, 33 one from Norway, 34 one from Spain 35 and one from Taiwan. 36…”

“…To evaluate differences in the stroke populations included in the different papers, especially those reporting NPV and/or specificity, it would be informative to investigate differences in severity, using NIHSS, between patient groups. However, only four papers reported NIHSS score, 15,19,23,24 and only one of these reported NPV or specificity, 24 making comparisons between papers with regard to true and false negatives impossible. Methodological differences did not allow for a direct comparison between studies by way of meta-analysis, and direct comparisons between settings were not possible.…”

“…If all EMS calls were sampled, we would expect a high specificity and NPV. 18,25,32,34 Some papers only included patients suspected of stroke while still providing specificity and/or NPV, 22,24,33 presumably calculated without including all true negatives, which could in part explain the observed variations. To evaluate differences in the stroke populations included in the different papers, especially those reporting NPV and/or specificity, it would be informative to investigate differences in severity, using NIHSS, between patient groups.…”