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.
European stroke journal · 2026-06-02 · Method & validation
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.