Neal S. Parikh, MD
Optimizing access to endovascular therapy has become a public health priority. While various national guidelines seek to shape acute stroke EMS triage practices broadly, regulatory bodies have also acknowledged the need to tailor protocols to local and regional environments.
In deciding whether to triage an individual patient with suspected stroke to an endovascular center instead of a primary stroke center, EMS may consider factors such as relative travel distances, stroke severity, and the likelihood of a large vessel occlusion (LVO).
LVO screening tools have inherent imprecision, and the positive predictive value, of course, depends on the prevalence of LVO. For this reason, knowing the prevalence of LVO among acute ischemic stroke 9-1-1 dispatches is of importance. Further, at an organizational level, the accuracy and precision of LVO detection in the field has upstream implications for case load at endovascular and non-endovascular centers. The importance of these considerations varies by locale.
Dozois and colleagues performed a cross-sectional study of patients encountered during dispatch for stroke-like symptoms and patients otherwise suspected to have stroke by EMS providers. From among 2,402 patients with suspected stroke, 485 were diagnosed with acute ischemic stroke (AIS), of which 117 had an LVO.
The false stroke diagnosis rate (of AIS) was 79.8%, which means that less than 1 in 4 patients suspected to have stroke by EMS ultimately had this diagnosis. Among patients with suspected stroke, the prevalence of LVO was low; however, among patients ultimately diagnosed with acute ischemic stroke, 1 in 4 had an LVO.
A key limitation is that the denominator was not suspected LVO; the reliability of pre-hospital LVO screening was not assessed in this study.
Nonetheless, these data are noteworthy for they highlight the challenges faced in developing pre-hospital triage protocols. The real-world unreliability of pre-hospital AIS diagnosis should be accounted for in pre-hospital triage protocol development.