Reliability, validity and responsiveness of the fear-avoidance beliefs questionnaire: methodological aspects of the Norwegian version.

OBJECTIVE To evaluate reliability, validity and responsiveness of the Fear-Avoidance Beliefs Questionnaire (FABQ) for use in Norwegian patients with low back pain. DESIGN A prospective cohort study with 2 groups. PATIENTS The questionnaire was tested in 123 patients with acute low back pain and 50 patients with chronic low back pain. METHODS A translation and cross-cultural adaptation was performed. Test-retest reliability was assessed in 28 patients with chronic low back pain. Responsiveness was assessed in acute low back pain. RESULTS Two factors for the FABQ were confirmed; fear-avoidance beliefs about work (FABQ-Work) and physical activity (FABQ-PA), accounting for 60% and 54% of the total variance in acute and chronic low back pain, respectively. For FABQ-Work and FABQ-PA internal consistency was 0.90 and 0.79, intra-class correlation coefficients 0.82 and 0.66, minimal detectable changes 12 and 9 points, and coefficients of variation were 16% and 23%. The FABQ correlated weakly to moderately with pain, disability, distress, and clinical variables. Standardized response means were low for FABQ-Work (0.32) and moderate (0.56) for FABQ-PA. Both FABQ subscales showed initially floor and/or ceiling effects. CONCLUSION The Norwegian FABQ version had acceptable factor structure, internal consistency, test-retest reliability and construct validity. The responsiveness of the FABQ-Work was low, and for the FABQ-PA moderate, in the acute sample.