Reliability, responsiveness and minimal clinically important difference of the two Fear Avoidance and Beliefs Questionnaire scales in Italian subjects with chronic low back pain undergoing multidisciplinary rehabilitation

BACKGROUND: The Fear-Avoidance Beliefs Questionnaire (FABQ) is a widely used outcome measure. There is still a lack of information concerning responsiveness and minimal clinically important difference (MCID), limiting its use for clinical and research purposes. AIM: To examine reliability, responsiveness and MCID of the two FABQ scales in subjects with chronic Low Back Pain. DESIGN: Methodological research based on a prospective single-group observational study. SETTING: Outpatient, rehabilitation unit. POPULATION: Chronic non-specific Low Back Pain. METHODS: At the beginning and the end of a multidisciplinary programme (8-week), 129 subjects completed the FABQ scales. Reliability was determined as internal consistency (Cronbach’s alpha) and test-retest reliability (96-hour interval; n= 64). Responsiveness was calculated both by distribution-based and anchor-based methods, using as external criterion the global perceived effect scale (GPE: 7 levels), rated by each individual. RESULTS: Cronbach’s alpha and ICC(2,1) were respectively: 0.75 and 0.90 for FABQ-Physical Activity scale (FABQ-PA), and 0.85 and 0.95 for FABQ-Work scale (FABQ-W). Minimum detectable change (MDC95) values were 3.69 points for FABQ-PA, and 5.95 points for FABQ-W. In receiver-operating characteristics curves, splitting GPE data into null/minimal/moderate improvement vs. large improvement (GPE 0-2 vs. GPE 3): 1) for FABQ-PA, the area under the curve (AUC) was 0.97. The best cutoff score identifying meaningful change in fear-avoidance beliefs about physical activity was a change of 4 points; 2) for FABQ-W, the AUC was 0.97 and the best cutoff score for meaningful change in fear-avoidance beliefs about work activities was a change of 7 points. CONCLUSIONS: After triangulation of the above results, a change of 4 points for FABQ-PA and 7 points for FABQ-W were selected as MCID. These two values represent cutoffs that seem to accurately identify meaningful change in fear-avoidance beliefs, according to subject’s judgement. CLINICAL REHABILITATION IMPACT: The present study calculated - in a sample of people with chronic Low Back Pain - the minimal clinically important change of the two FABQ scales (FABQ-Physical Activity scale and FABQ-Work scale). These values increase confidence in interpreting score changes, thus enhancing their meaningful use in both research and clinical contexts