Diagnostic performance of prehospital large-vessel occlusion detection scales in patients with suspected acute stroke: a retrospective validation study. The Akershus Study of Ischemic Stroke and Thrombolysis

Abstract Introduction Prehospital stroke scales are widely used to identify patients with suspected stroke. The scales have shown potential to identify suspected large-vessel occlusion (LVO) for direct-to-thrombectomy triage, yet it remains unclear which scales perform best, and whether performance varies by patient characteristics. Patients and methods In this retrospective diagnostic accuracy study, we analysed 1150 consecutive adults admitted under the stroke code protocol at a primary stroke centre (January 2015–December 2017). The cohort included ischaemic stroke, transient ischaemic attack, intracerebral haemorrhage and mimics. We evaluated 55 scale–threshold combinations (46 scales) for detection of computed tomography angiography (CTA)–confirmed LVO, quantified by area under the receiver operating characteristic curve (AUC), sensitivity, specificity and predictive values. Results In our study population, LVO prevalence was 13.5%. AUC ranged from 0.586 (Hemiplegia) to 0.855 (FAST-ED). No scale significantly outperformed the continuous National Institutes of Health Stroke Scale (NIHSS, AUC 0.851) after Bonferroni correction, and none achieved both sensitivity and specificity above 80%. Scales combining cortical and motor items outperformed purely motor-based instruments. Accuracy was comparable between sexes but higher for left-hemispheric strokes (mean AUC: 0.82 vs 0.76) and patients aged ≥60 years (0.82 vs 0.77). Discussion None of the prehospital stroke scales were accurate enough to reliably detect LVO. Performance varied with stroke laterality, patient age and stroke severity—approaching chance levels at the extremes of severity and showing a consistent hemispheric bias. Conclusion This highlights fundamental limitations of using clinical scales alone to detect LVO in real-world stroke code populations. Registration: ClinicalTrials.gov, https://clinicaltrials.gov/study/NCT05378490, NCT05378490.