Measurement properties of the Trunk Impairment Scale-modified Norwegian version among people with mild to moderate multiple sclerosis

The Trunk Impairment Scale–modified Norwegian version (TIS-modNV) measures trunk control for clinical and research purposes. This study examined the validity and reliability of the TIS-modNV in people with multiple sclerosis (pwMS). Sixty-eight pwMS (mild to moderate) participated. The TIS-modNV and the Mini-Balance Evaluation Systems Test (Mini-BESTest) scores were compared for <i>construct validity</i> using Spearman’s rho (<i>r_s</i>). TIS-modNV performance was videotaped and rated by four physiotherapists on two occasions. The <i>inter-</i> and<i> intrarater reliability</i> was analyzed via intraclass correlation coefficients (ICC), standard errors of measurement (SEM), Bland–Altman plots, and kappa statistics (<i>k</i>). Validity was demonstrated (<i>r_s</i> = 0.55–0.61). Interrater reliability for the total score was moderate to good (ICC(A,1) =0.67; ICC(C,1) = 0.78), and the SEM was 2 points (12.8%). Interrater reliability varied across the rater pairs (ICC(A,1) = 0.54-0.81) as displayed in the Bland–Altman plots. Item-level interrater agreement varied from poor to good (<i>k</i> = 0.10–0.79). Intrarater reliability of the total scores was moderate to good (ICC(A,1) = 0.67–0.82). This study supports the construct validity and overall reliability of the TIS-modNV in pwMS with mild to moderate disability. However, variations in rater reliability need to be addressed. The Trunk Impairment Scale – modified Norwegian version (TIS-modNV) can be used to assess impairments in trunk control among people with mild to moderate multiple sclerosis (MS).Results of this study support construct validity and overall reliability of the TIS-modNV in individuals with MS.To address concerns about reliability, comprehensive training for raters and caution when comparing scores obtained by different raters are recommended. The Trunk Impairment Scale – modified Norwegian version (TIS-modNV) can be used to assess impairments in trunk control among people with mild to moderate multiple sclerosis (MS). Results of this study support construct validity and overall reliability of the TIS-modNV in individuals with MS. To address concerns about reliability, comprehensive training for raters and caution when comparing scores obtained by different raters are recommended.