A further Rasch analysis of the Fear-Avoidance Beliefs Questionnaire in adults with chronic low back pain suggests the revision of its rating scale

Objective: To examine the psychometric properties of the Fear-Avoidance Beliefs Questionnaire (FABQ) and its two subscales, in subjects with chronic low back pain (LBP). Design: Methodological research based on a cross-sectional observational study. Methods: A convenience sample of 155 Italian subjects with chronic LBP (57% men; mean age: 43±11 years; mean pain duration: 23±32 months) completed the FABQ. Rasch analysis was used to investigate dimensionality of the entire scale and key psychometric properties of its two subscales. Results: The FABQ-Physical Activity (FABQ-PA) and FABQ-Work (FABQ-W) subscales showed two distinct unidimensional structures. Their 7-option rating categories were malfunctioning, but after collapsing problematic categories and omitting the central one ("Unsure") the new 4 categories (completely disagree; disagree; agree; completely agree) functioned as intended. After that and accommodation of local response dependency between two items in a testlet solution, each of the two subscales presented acceptable fit to the Rasch model (just one FABQ-W items was slightly underfitting). Person separation reliability was acceptable but not high (0.69 for FABQ-PA, and 0.79 for FABQ-W). Conclusions: FABQ-PA and FABQ-W have adequate unidimensionality. A simplification of the response options of both subscales is strongly recommended to improve the technical quality of the scale. The reliability indexes suggest FABQ-PA and FABQ-W can be used for group judgements about level of fear-avoidance beliefs, but not for clinical decision-making in individuals. The selection of their items is acceptable, although - if future studies corroborate our results - there is room for some refinements to improve the general measurement quality. Clinical rehabilitation impact: Fear-avoidance beliefs are associated with reduction of physical activity, and development of disability and deconditioning. This study examined the measurement properties of the two FABQ subscales, showing their essential unidimensionality, recommending the simplification of the rating categories, and discussing strengths and weaknesses of item selection. Our results extend the evidence for FABQ as a satisfactory (but improvable) measure of fear-avoidance beliefs in chronic LBP.