Abstract WP276: Simplification of a Prehospital Short NIHSS Scale Does not Increase Interrater Agreement Between Emergency Medical Services and Stroke Specialists

Abstract

Objective: To assess if simplifying a prehospital 8-item NIHSS scale (NIHSS-8, fig 1) to a 0 (symptom absent) – 1 (symptom present) scoring system increases interrater agreement between emergency medical services (EMS) and stroke specialists. Methods: We analysed interrater agreement between EMS and stroke specialists of a single centre on a prospectively collected cohort of 64 suspected acute ischemic stroke patients. EMS performed NIHSS-8 score upon patient arrival at the emergency department. The stroke specialist scored the full 15-item NIHSS blind to the EMS scores and within 5 minutes of patient arrival. Linear-weighted Cohen’s kappa statistics was used to assess agreement between EMS and stroke specialist on the total NIHSS-8 score and each NIHSS-8 scale item. We then simplified each item to a 0-1 score and reassessed interrater agreement for the overall NIHSS-8 scale using linear-weighted Cohen’s kappa statistics and for each NIHSS-8 item using Cohen’s kappa statistics. We used Cohen’s kappa statistics to assess agreement for original and simplified NIHSS-8 cut-off scores. Results: EMS and stroke specialist reached substantial agreement on overall NIHSS-8 scoring (linear-weighted kappa 0.69). Optimum agreement was reached for right arm weakness (linear-weighted kappa 0.79; Table 1) and a cut-off score of 2 and 5 (Cohen’s kappa 0.78; Table 2). When the score was simplified to a 0-1, overall agreement between EMS and stroke specialists was substantial (linear-weighted kappa 0.65). Optimum agreement was seen for LOC questions (Cohen’s kappa 0.78; Table 1) and a cut-off score of 2 (Cohen’s kappa 0.77; Table 2). Conclusion: Simplifying an 8-item prehospital NIHSS stroke scale does not increase interrater agreement between emergency medical services and stroke specialists.