The Generic BFRB Scale-8 (GBS-8): a transdiagnostic scale to measure the severity of body-focused repetitive behaviours.

Background: Body-focused repetitive behaviours (BFRBs) such as skin picking and hair pulling are frequent but under-diagnosed and under-treated psychological conditions. As of now, most studies use symptom-specific BFRB scales. However, a transdiagnostic scale is needed in view of the high co-morbidity of different BFRBs.
Aims: We aimed to assess the reliability as well as concurrent and divergent validity of a newly developed transdiagnostic BFRB scale.
Method: For the first time, we administered the 8-item Generic BFRB Scale (GBS-8) as well as the Repetitive Body Focused Behavior Scale (RBFBS), modified for adults, in 279 individuals with BFRBs. The GBS-8 builds upon the Skin Picking Scale-Revised (SPS-R), but has been adapted to capture different BFRBs concurrently. A total of 170 participants (61%) were re-assessed after 6 weeks to determine the test-retest reliability of the scale.
Results: Similar to the SPS-R, factor analysis yielded two dimensions termed symptom severity and impairment. The test-retest reliability of the scale was satisfactory ( r = .72, p <.001). Concurrent validity ( r = .74) with the RBFBS was good (correlational indexes for concurrent validity were significantly higher than that for discriminant validity).
Discussion: The GBS-8 appears to be a reliable and valid global measure of BFRBs. We recommend usage of the scale in combination with specific BFRB scales to facilitate comparability across studies on obsessive-compulsive spectrum disorders.