Development, reliability, and validity of a novel Epidermolysis Bullosa Disease Activity and Scarring Index (EBDASI)

Abstract

There is a lack of validated standardized outcome measures for epidermolysis bullosa (EB) that can separate activity from damage. We sought to develop and validate an instrument for inherited EB of all ages and subtypes, the EB Disease Activity and Scarring Index (EBDASI), which scores activity responsive to therapy separately from scarring. The EBDASI was validated by comparing its reliability and validity against the Birmingham EB Severity (BEBS) score (partially validated with activity mixed with scarring), using the Physician Global Assessment (PGA) scale as a reference measurement. Sixteen patients with EB (7 EB simplex, 5 dominant dystrophic EB [DDEB], 2 junctional EB, and 2 recessive dystrophic EB) were assessed by 5 EB experts using the EBDASI, BEBS, and PGA, and data from 9 additional patients assessed on an ad hoc basis during routine patient clinic were also included. For interrater reliability, the overall total score intraclass correlation coefficients (95% confidence intervals) were: EBDASI 0.964 (0.929-0.986), BEBS 0.852 (0.730-0.937), and PGA 0.873 (0.765-0.946). For intrarater reliability, the intraclass correlation coefficients were: EBDASI 0.994 (0.976-0.998), BEBS 0.926 (0.748-0.981), and PGA 0.932 (0.764-0.982). The EBDASI had a higher correlation with PGA (ρ = 0.871) than BEBS with PGA (ρ = 0.852). Intraclass correlation coefficients scatterplots showed the EBDASI was better at distinguishing milder forms of EB, with better correlations at higher severity scores than the BEBS. A limited number of patients were recruited for this study. An independent study will be required to demonstrate the responsiveness of the EBDASI. The EBDASI demonstrated excellent reliability and validity, as compared with 2 other outcome measures.