A major obstacle in performing multicenter controlled trials for pemphigus is the lack of a validated disease activity scoring system. Here we assess the reliability and convergent validity of the PDAI (pemphigus disease area index). A group of 10 dermatologists scored 15 patients with pemphigus to estimate the inter- and intra-rater reliability of the PDAI and the recently described ABSIS (autoimmune bullous skin disorder intensity score) instrument. To assess convergent validity, these tools were also correlated with the Physician’s Global Assessment (PGA). Reliability studies demonstrated an intra-class correlation coefficient (ICC) for inter-rater reliability of 0.76 [95% CI = 0.61–0.91] for the PDAI and 0.77 [0.63–0.91] for the ABSIS. The tools differed most in reliability of assessing skin activity, with an ICC of 0.39 [0.17–0.60] for the ABSIS and 0.86 [0.76–0.95] for the PDAI. Intra-rater test-retest reliability demonstrated an ICC of 0.98 [0.96–1.0] for the PDAI and 0.80 [0.65–0.96] for the ABSIS. The PDAI also correlated more closely with the PGA. We conclude that the PDAI is more reproducible and correlates better with physician impression of extent. Subset analysis suggests that for this population of mild to moderate disease activity, the PDAI captures more variability in cutaneous disease than the ABSIS.

Background-Reliable and validated measures of skin disease severity are needed for cutaneous dermatomyositis (DM). CDASI (Cutaneous Dermatomyositis Disease Area and Severity Index), DSSI (Dermatomyositis Skin Severity Index), and CAT (Cutaneous Assessment Tool) skin indices have been developed as outcome instruments.

Background-Quality of life (QoL) for patients with inflammatory skin disease can be significant, but has been evaluated in just one study in dermatomyositis (DM).

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Background To properly evaluate therapies for cutaneous dermatomyositis (DM), it is essential to administer an outcome instrument that is reliable, valid, and responsive to clinical change, particularly when measuring disease activity. Objective The purpose of this study is to compare two skin-severity DM outcome measures, the Cutaneous Disease and Activity Severity Index (CDASI) and the Cutaneous Assessment Tool-Binary Method (CAT-BM), with the physician global assessment (PGA) as the ‘gold standard’. Methods Ten dermatologists evaluated fourteen patients with DM using the CDASI, CAT-BM, and PGA scales. Inter-, intra-rater reliability, validity, responsiveness, and completion time were compared for each outcome instrument. Responsiveness was assessed from a different study population, where one physician evaluated 35 patients with 110 visits. Results The CDASI was found to have a higher inter- and intra-rater reliability. Regarding construct validity, both the CDASI and the CAT-BM were significant predictors of the PGA scales. The CDASI had the best responsiveness among the three outcome instruments examined. The CDASI had a statistically longer completion time than the CAT-BM by about 1.5 minutes. Limitations The small patient population may limit the external validity of the findings observed. Conclusions The CDASI is a better clinical tool to assess skin severity in DM.