Validation of the Investigator's Global Assessment Scale for Epidermolysis Bullosa Simplex

ABSTRACT Background There is a lack validated outcome measures to assess wound severity in epidermolysis bullosa simplex (EBS). Objectives To assess the reliability and validity of the Investigator's Global Assessment (IGA) scale and a newly developed palms/soles subscale through in‐clinic scoring and review of patient‐submitted photographs. Methods Seven eligible patients with biopsy‐proven or genetically confirmed diagnosis of EBS were recruited. Seven expert raters graded 30 wounds at a 1‐day in‐clinic scoring exercise using an IGA scale that was previously developed for assessing wound severity in EBS clinical trials. A new palms/soles subscale was developed by the authors for palms and soles wounds. Reliability and construct validity with the Epidermolysis Bullosa Disease Activity and Scarring Index‐Activity (EBDASI‐Activity) subscore, target wound blister count, the Quality of Life in Epidermolysis Bullosa (QOL‐EB) questionnaire, itch and pain measures were assessed. Photographs of the same wounds provided by the patients were sent to the same raters to evaluate intra‐rater reliability through a virtual exercise. Results Seven clinicians with EB expertise assessed 30 target wounds. Patients (female n = 5/7) had a mean age of 28.3 years (range 7.1–48.8 years). Strong inter‐rater reliability was observed for the in‐clinic scoring (Kendall's coefficient of concordance, 0.77; intraclass coefficient, 0.70) with excellent agreement (weighted quadratic kappa, 0.86). A positive association with target wound blister count, EBDASI‐Activity, and itch and pain scores were observed. Home photograph scoring also showed strong inter‐rater reliability and excellent agreement (Kendall's coefficient of concordance, 0.78; weighted quadratic kappa, 0.84; intraclass coefficient, 0.66). When home‐photograph scores were compared to in‐clinic scores rendered on corresponding wounds, strong intra‐rater and substantial agreement was demonstrated (Kendall's coefficient of concordance, 0.86; weighted quadratic kappa, 0.67; intraclass coefficient, 0.68). Conclusions The IGA scale for EBS demonstrated strong reliability and excellent agreement in assessing wound severity of target lesions both in‐clinic and via patient‐submitted photographs.