Background: The National Institutes of Health Stroke Scale (NIHSS) was not intended to be used to determine the stroke’s vascular distribution. The aim of this study was to develop, assess the reliability, and validate a computer algorithm based on the NIHSS for this purpose.
Methods: Two cohorts of patients with ischemic stroke having similar distributions of Oxfordshire localizations (total anterior, partial anterior, lacunar, and posterior circulation) based on neuroimaging were identified. The first cohort (n=40) was used to develop a computer algorithm for vascular localization using a modified version of the NIHSS (mNIHSS) that included selected deficit laterality; the second (n=20) was used to assess the reliability of algorithm-based localizations compared to those of two vascular neurologists. The validity of the algorithm-based localizations was assessed in comparison to neuroimaging. Agreement was assessed using the un-weighted kappa K) statistic.
Results: Agreement between the two raters using the standard NIHSS was slight to moderate (K=0.36, 95% CI 0.10-0.61). Inter-rater agreement significantly improved to the substantial to almost perfect range using the mNIHSS (K=0.88, 95% CI 0.73-1.00). Agreement was perfect when the two raters entered the data into the mNIHSS computer algorithm (K=1.00, 95% CI 1.00-1.00). Agreement between the algorithm localization and neuroimaging results was fair to moderate (K=0.59, 95% CI 0.35-0.84) and not significantly different than the localizations of either rater using the mNIHSS.
Conclusion: A computerized, modified version of the standard NIHSS can be used to reliably and validly assign the vascular distribution of an acute ischemic stroke.