The Short-Form Neck Disability index has adequate measurement properties in chronic neck pain patients

OBJECTIVES: To assess test–retest reliability, internal consistency, construct validity, and the presence of ceiling and floor effects in the Brazilian version of the Short-Form Neck Disability Index (SF-NDI) in patients with chronic neck pain. METHODS: One hundred and fifty-six patients answered the Numerical Pain Rating Scale (NPRS), Short-Form Neck Disability Index (SF-NDI), Tampa Scale of Kinesiophobia (TKS), Pain Catastrophizing Scale (PCS), and the 36-Item Short-Form Health Survey questionnaire (SF-36). Another sample (n = 51) filled the SF-NDI at two different times, and test–retest reliability was measured using the intraclass correlation coefficient (ICC), standard error of measurement (SEM), and minimum detectable change (MDC). The internal consistency of the SF-NDI was analyzed by Cronbach's alpha. To determine construct validity, Spearman's correlation coefficient was used to determine the magnitude of the correlation between the score of the SF-NDI and other measurement instruments: NPRS, TKS, PCS, SF-36, and original NDI. RESULTS: SF-NDI presented substantial reliability (ICC = 0.844) and adequate internal consistency (Cronbach's alpha = 0.778). We observed significant values and with a correlation magnitude greater than 0.80 for the SF-NDI with the original NDI, between 0.30 and 0.50 for the correlations with TKS, and the functional capacity and pain domains of the SF-36, and less than 0.30 with the other study instruments. No participant reached the maximum score. Ceiling and floor effects were not observed. CONCLUSIONS: SF-NDI with 5 items has adequate measurement properties in Brazilian chronic neck pain patients. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00586-021-07019-4.