The reliability and validity of outcome measures for atopic dermatitis in patients with pigmented skin: A grey area

Background: Outcome measures for atopic dermatitis (AD) patients with pigmented skin have neither been developed nor validated. Objective: To compare the reliability and validity of four common AD outcome measures in patients with various levels of skin darkness. Method: The inter- and intra-rater reliability and construct validity of the EASI (Eczema Area and Severity Index), objective-SCORing Atopic Dermatitis (oSCORAD), Three Items Severity index (TIS) and Six Areas, Six Sites Atopic Dermatitis (SASSAD) were evaluated in 18 patients of various levels of skin darkness, using their full body photographs, by five trained clinicians. Results: The inter-rater reliability intraclass coefficient (ICCs) and 95% confidence intervals were poor for highly pigmented patients: EASI -054(-200 to .657), oSCORAD -089(-206 to .598), TIS -21(-24 to .147), SASSAD -071(-200 to .631); fair for mildly pigmented patients: EASI .464(140-839), oSCORAD .588(265-89), TIS.524(200-865), SASSAD .41(045-775); and fair to good for non-pigmented patients: EASI .64(330-908), oSCORAD .586(263-889), TIS .403(09-809), SASSAD .667(358-916). Erythema likely contributed to the inter-rater variability. Construct validity had significant correlations across all measures in non-pigmented patients, but no correlations in highly pigmented patients. Conclusion: AD outcome measures have poor reliability and validity in highly pigmented patients, with variations in erythema perception being a contributor.