620 Initial validation of the IGA x BSA in atopic dermatitis

Abstract

Various clinical outcome measures exist to assess atopic dermatitis (AD) severity in clinical trials but, due to their complexity, these instruments may not be suitable for clinical practice. The product of a physician-derived global assessment and body surface area (PGA x BSA) has been proposed as an instrument to quickly assess the severity of signs in psoriasis in clinical practice. The primary objective of this study was to investigate the construct validity of this outcome measure in patients with AD in the clinical setting. We performed a retrospective chart review of patients with AD seen in an outpatient dermatology clinic at Oregon Health & Science University from 2015-2018 who had a recorded BSA and a 5-point global assessment recorded by an investigator (IGA). We identified 246 patients comprising 682 clinic visits with recorded outcome measures. We observed strong and statistically significant correlations between IGA x BSA and EASI (r=0.9105, p <0.0001, n=19). IGA x BSA also showed strong correlations with the average daily pruritus NRS (r=0.7108, p <0.0001, n=177) and the patient global assessment (r=0.7389, p <0.0001, n=170). Furthermore, the BSA x IGA correlated with a derived global scale, similar to that used in psoriasis trials, comprised of the average of four signs rated between 0-3 (r=0.7652, p <0.0001, n=282). The results from this study suggest that IGA x BSA is a valid and feasible outcome measure that may be used as a proxy for EASI in clinical practice. Additionally, IGA x BSA demonstrated evidence of convergent validity with PROs, further emphasizing its utility in a real-world clinical setting.