The neurological fatigue index for stroke. Reliability of a Norwegian version

The aim of this study was to examine the test-retest reliability, internal consistency, and floor and ceiling effects of a Norwegian version of the Neurological Fatigue Index for Stroke (NFI-Stroke).

To evaluate the psychometric properties of the NFI-Stroke, persons with stroke were recruited. Inclusion criteria were: ≥18 years; a performance of ≥4 seconds on the Clock-Drawing Test; and participants had to speak and understand Norwegian. Test-retest reliability, internal consistency, and floor and ceiling effects were evaluated with Spearman's rho, Weighted Kappa, Cronbach's Alpha, corrected total-item correlation, percentage of the total score, and responses to each item.

Of 82 eligible, 66 respondents were included in the project. NFI-Stroke has a test-retest reliability of 0.89, 0.89, and 0.87 with Spearman's rho and 0.55-0.78 with Weighted Kappa. For the subgroup chronic stroke, Spearman's rho was 0.89, 0.86, and 0.93, and Weighted Kappa was 0.61-0.91. For the subgroup sub-acute stroke, Spearman's rho was 0.48, 0.55, and 0.51, and Weighted Kappa was 0.02-0.54. Cronbach's Alpha was 0.90. For the physical subscale, alpha was 0.89, and for the cognitive subscale 0.74. Corrected total-item correlation for NFI-Stroke was 0.50-0.78, 0.55-0.79 for the physical subscale, and 0.46-0.60 for the cognitive subscale. None scored the highest nor lowest possible score of the questionnaire.

NFI-Stroke has high test-retest reliability, and high internal consistency with neither floor nor ceiling effects for persons with stroke. The questionnaire may be useful both in general rehabilitation in institutions as well as in the municipal health services.