Content and construct validity, predictors, and distribution of self-reported atopic dermatitis severity in US adults

Background: Atopic dermatitis (AD) is associated with skin lesions, multiple symptoms, and effect of quality of life, all of which factor into disease severity. Self-reported global AD severity may be a valid severity assessment for epidemiologic research. Objective: To validate self-reported global AD severity in a representative cohort of adults with AD. Methods: Preliminary probing-cognitive interviews were performed (n = 8). Next, a cross-sectional US population-based survey study of adults with AD was performed. AD was diagnosed using an adap/tation of the UK Working Party criteria (n = 602). AD severity was assessed using self-reported global AD severity (mild, moderate, severe), Patient-Oriented Scoring AD (PO-SCORAD), Patient-Oriented Eczema Measure (POEM), Numeric Rating Scale (NRS)–itch, NRS-sleep, NRS-pain, and Hospital Anxiety and Depression Scale (HADS). Results: Self-reported global AD severity had good content validity. Self-reported global AD severity had strong correlations with PO-SCORAD (Spearman correlation ρ = 0.61) and objective PO-SCORAD (ρ = 0.61); moderate correlations with POEM (ρ = 0.54), NRS-itch (ρ = 0.44), NRS-pain (ρ = 0.46), and HADS (ρ = 0.41); and weak correlation with NRS-sleep (ρ =.32) (P <.001 for all). Consistent and significant correlations were observed in stratified analyses by age, sex, race/ethnicity, and level of education. There were stepwise increases of PO-SCORAD, NRS-itch, NRS-sleep, NRS-pain, POEM, and HADS with increasing self-reported global AD severity (Kruskal-Wallis test, P <.01). There was weak-moderate concordance between self-reported AD severity and established severity strata for PO-SCORAD (ρ = 0.44), NRS-itch (ρ = 0.30), and POEM (ρ = 0.43). Rather, self-reported global AD severity was best predicted by a combination of PO-SCORAD, POEM, NRS-itch, NRS-pain, and HADS. No differential item reporting was found by age, sex, or race/ethnicity. Conclusion: Self-reported AD severity simultaneously assesses multiple AD constructs and appears to be sufficiently valid for assessing AD severity in clinical and epidemiologic studies.