Validity and Reliability of a Korean Version of the National Institutes of Health Stroke Scale

BACKGROUND AND PURPOSE The National Institutes of Health Stroke Scale (NIHSS) is a clinical assessment tool that is widely used in clinical trials and practice to evaluate stroke-related neurological deficits. The aim of this study was to determine the validity and reliability of the Korean version of the NIHSS (K-NIHSS) for evaluating Korean stroke patients. METHODS The K-NIHSS was translated and adapted with regard to cultural and linguistic peculiarities. To examine its content validity, we quantified the Content Validity Index (CVI), which was rated by 11 stroke experts. The validity of the K-NIHSS was assessed by comparison with the Glasgow Coma Scale (GCS), the modified Rankin Scale (mRS), and the Barthel Index. The reliability of the K-NIHSS was evaluated using the unweighted kappa statistics for multiple raters and an intraclass correlation coefficient (ICC). RESULTS The CVI of the K-NIHSS reached 0.91-1.00. The median K-NIHSS score at baseline was 3 (interquartile range, 2-7), and the mean±SD score was 6.0±6.6. The baseline K-NIHSS had a significantly negative correlation with the GCS at baseline and the Barthel Index after 90 days. The K-NIHSS also had a significantly positive correlation with the mRS after 90 days. Facial paresis and dysarthria had moderate interrater reliability (unweighted kappa, 0.41-0.60); kappa values were substantial to excellent (unweighted kappa, >0.60) for all the other items. The ICC for the overall K-NIHSS score was 0.998. The intrarater reliability was acceptable, with a median kappa range of 0.524-1.000. CONCLUSIONS The K-NIHSS is a valid and reliable tool for assessing neurological deficits in Korean acute stroke patients.