Rasch analysis of the Neck Bournemouth Questionnaire to measure disability related to chronic neck pain.

OBJECTIVE To determine the psychometric properties of the Neck Bournemouth Questionnaire in patients with chronic neck pain, using Rasch analysis. METHODS A sample of 161 subjects with chronic neck pain was assessed with the Neck Bournemouth Questionnaire. Before performing Rasch analysis, we examined the structure of the scale with factor analysis. The goodness-of-fit of the data to the model, thresholds ordering, unidimensionality, local independence of the items, differential item functioning, person separation index, and mean person's location were assessed. RESULTS Both exploratory and confirmatory factor analyses supported the presence of 2 factors. Only Factor 1 needed a modification (item 7 removal) in order to achieve the fit to the Rasch model (χ2 = 10.65, df 8, p = 0.22). The person separation index was 0.80 and the mean location of persons 0.48 (standard deviation (SD) 1.02). Factor 2 (items 4 and 5) fitted the model without modifications (χ2 = 3.86, df 4, p = 0.42). Its person separation index and mean person's location were, respectively, 0.77 and -0.71 (SD 1.57). CONCLUSION The Neck Bournemouth Questionnaire with the purposed modification may provide useful clinical profiles and change scores of subjects with chronic neck pain for research purposes.