Back Beliefs Questionnaire: A cross-cultural measurement study.

BACKGROUND: The Back Beliefs Questionnaire (BBQ) is frequently used to identify beliefs about inevitable consequences of low back pain, but its measurement properties are not yet fully known. OBJECTIVE: To evaluate the BBQ's validity and reliability in people with low back pain from Australia and Brazil. DESIGN: Cross-sectional study with a retest sample, following COSMIN guidelines. METHODS: We used data from two independent cross-sectional studies, each with a subsample of repeated measurements in stable patients. A total of 466 people (258 Australian,208 Brazilian) were included, with self-reported low back pain in the last year. Participants completed an online survey including English (Australia-based) or Portuguese (Brazil-based) versions of the BBQ. Each version was evaluated separately for structural validity (Confirmatory Factor Analysis (CFA)), internal consistency (Cronbach's alpha), test-retest reliability (intra-class correlation coefficient), measurement error (smallest detectable change), and construct validity (hypothesis testing). Cross-cultural validity was assessed for the first time using multigroup CFA. RESULTS: Both versions had a unidimensional structure confirmed for scoring items, with adequate internal consistency and reliability (>0.70). Pearson test confirmed, for both language versions, our validity hypotheses of negative correlation (0.20 to 0.60) between BBQ and Numeric Pain Rating Scale and Roland-Morris Disability Questionnaire. Cross-cultural validity analyses supported configural and metric invariance. However, partial scalar invariance indicates that comparisons involving the underlying construct are appropriate, but comparisons of mean scores between countries should be interpreted with caution. CONCLUSION: Both Australian and Brazilian BBQ versions have some sufficient measurement properties, but further research is needed to confirm its validity.