Establishment of the Thai version of National Institute of Health Stroke Scale (NIHSS) and a validation study

Background: The National Institute of Health Stroke Scale (NIHSS) is a well validated stroke severity assessment scale. The scale is used to assess neurological deficits, progression and degree of recovery in acute stroke settings. To date, no Thai version exists. Objective: This study aimed to adapt and validate a Thai version of the NIHSS (NIHSS-T). Material and Method: A cross-cultural adaptation of the NIHSS was developed according to the methods recommended by the International Quality of Life Assessment Project Group. Forward and backward translations were performed. A final version of the NIHSS-T was validated against initial MRI infarction volume and modified Rankin Scale (mRS) at 3 months in a consecutive series of acute stroke patients. The patients were prospectively evaluated by 3 different types of health care providers: 2 stroke fellows, 2 internists, and 2 stroke nurses. Mean NIHSS-T scores from all raters were used in the analysis. Results: The study included 32 acute ischemic stroke patients with a mean age (± SD) of 64.53 ± 14.97 years of age. Men comprised 71.9%. Mean NIHSS-T score (± SD) was 7.49 ± 7.02. Intra-observer reliability demonstrated a high agreement with an intraclass correlation (ICC) of 0.98, 0.98, 0.96, 0.98, 0.90 and 0.98 for 2 stroke fellows, 2 internists and 2 stroke nurses respectively. Inter-observer reliability between 6 raters was excellent, i.e.; ICC, 0.99 (0.98, 0.99). Spearman rank correlation coefficients between the initial NIHSS-T score versus initial MRI lesion volume and mRS at 3 months were 0.53 and 0.69 with a p-value of 0.002 and < 0.001 respectively. Conclusion: The Thai version of NIHSS is valid for assessing acute stroke severity. The scale is also reliable when administered in a Thai-speaking setting by trained healthcare professionals.