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

Abstract

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.

Fig 1.

Spearman correlations were performed that compared baseline scores of vIGA*BSA, vIGA*cBSA, BSA, EASI, and objective-SCORAD with each other, and patient-reported severity assessments for atopic dermatitis, itch and quality of life. Results are presented overall, and separately in children and adults. Spearman correlations were also performed that compared changes of scores from baseline at follow-up for vIGA*BSA, vIGA*cBSA, BSA, EASI, and objective-SCORAD with each other, and changes of patient-reported severity assessments for atopic dermatitis, itch and quality of life. Values are presented using a color-gradient from dark red (highest) to white (lowest). * P<0.05, ** P<0.01, *** P<0.0001