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

The aim of this study was 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, Unit of rehabilitation.

POPULATION

Chronic non-specific low back pain.

METHODS

At the beginning and the end of a multidisciplinary program (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; Interclass correlation coefficient [ICC 2.1]). 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 characteristic 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 and 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.