Measurement properties of the product of investigator's global assessement and body surface area in children and adults with atopic dermatitis.

BACKGROUND Multiple clinician-reported outcome measures exists for atopic dermatitis (AD) severity. However, there is no gold-standard for use in clinical practice. OBJECTIVES Determine the measurement properties of the product of validated Investigator's Global Assessment for AD (vIGA) and Body Surface Area (BSA) overall or divided into 6-categories (cBSA: 0%/0.1-<10%/10-<30%/30-<50%/50-<70%/70-<90%/90-100%) and compare with other clinician-reported and patient-reported outcomes in adults and children with AD. METHODS We performed a prospective dermatology practice-based study using questionnaires and evaluation by a dermatologist (n=653). RESULTS vIGA*BSA and vIGA*cBSA had good convergent validity with BSA (Spearman rho=0.97 and 0.93), eczema area and severity index (rho=0.94 and 0.92) and objective-SCORAD (rho=0.88 and 0.89); weak to good convergent validity with Numeric Rating Scale average-itch (rho=0.22 and 0.22) and worst-itch (rho=0.27 and 0.28), Patient-Oriented Eczema Measure (rho=0.44 and 0.43), Dermatology Life Quality Index (rho=0.48 and 0.49), ItchyQOL (rho=0.45 and 0.46), PROMIS Sleep Disturbance (rho=0.46 and 0.37) and Sleep related-impairment (rho=0.31 and 0.31) in adults and/or children; very good discriminant validity for physician-reported global AD severity; good responsiveness to change of severity of AD and itch; good reliability (intraclass correlation coefficient [95% confidence interval]: 0.72 [0.60-0.81] and 0.74 [0.62-0.82]); with no floor or ceiling effects. Thresholds for interpretability bands and clinically important difference were established. CONCLUSIONS vIGA*BSA and vIGA*cBSA scores showed good convergent and discriminant validity, reliability, responsiveness and interpretability in adults and children with AD, and were feasible for use in clinical practice. vIGA*BSA and vIGA*cBSA had slightly lower convergent validity than EASI or objective-SCORAD, but might be more efficient to collect and score.