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

BACKGROUND

Multiple clinician-reported outcome measures exist for atopic dermatitis (AD) severity. However, there is no gold standard for use in clinical practice.

OBJECTIVES

To 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 six categories (cBSA: 0%/0.1, <10%/10, <30%/30, <50%/50, <70%/70 and <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's ρ = 0.97 and 0.93), eczema area and severity index (ρ = 0.94 and 0.92), and objective SCORAD (ρ = 0.88 and 0.89); and weak-to-good convergent validity with Numeric Rating Scale average itch (ρ = 0.22 and 0.22) and worst itch (ρ = 0.27 and 0.28), Patient-Oriented Eczema Measure (ρ = 0.44 and 0.43), Dermatology Life Quality Index (ρ = 0.48 and 0.49), ItchyQOL (ρ = 0.45 and 0.46), PROMIS Sleep Disturbance (ρ = 0.46 and 0.37) and sleep-related impairment (ρ = 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; and 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.