title: Validation of the Cutaneous Dermatomyositis Disease Area and Severity Index: characterizing disease severity and assessing responsiveness to clinical change.
abstract: BACKGROUND
  The Cutaneous Dermatomyositis Disease Area and Severity Index (CDASI) was developed for use in clinical trials and longitudinal patient assessment.
  
  
  OBJECTIVE
  To characterize disease severity using the CDASI and assess the responsiveness of this instrument to clinically meaningful changes in disease activity.
  
  
  METHODS
  Patients with cutaneous dermatomyositis at the University of Pennsylvania (UPenn, n = 93) and Stanford University (Stanford, n = 106) were prospectively evaluated using the CDASI, physician global assessment (PGA) Likert scales and a visual analogue scale (VAS). Data was analysed using logistic regression models and receiver operating characteristic curves to select cut-offs.
  
  
  RESULTS
  Baseline CDASI activity scores for the patients evaluated at UPenn ranged from 0 to 47 (median 17), and baseline PGA VAS scores ranged from 0 to 9·6 (median 1·1). At UPenn a CDASI activity score of 19 differentiated mild from moderate and severe disease. At Stanford baseline CDASI scores ranged from 0 to 48 (median 21), baseline PGA VAS scores ranged from 0 to 9·7 (median 4·2) and CDASI activity scores of 14 or less characterized mild disease. When a 2-cm change in the PGA VAS was regarded as a clinically significant improvement, a 4-point (UPenn) or 5-point (Stanford) change in CDASI reflected a minimal clinically significant response.
  
  
  CONCLUSIONS
  The CDASI is a valid and responsive measure that can be used to characterize cutaneous dermatomyositis severity and detect improvement in disease activity. Variations in cut-offs may be due to differences in disease severity between the two populations or inter-rater variations in the use of the external gold measures.
authors.affiliation: Philadelphia Veterans Affairs Medical Center, Philadelphia, PA, U.S.A.|Department of Dermatology, University of Pennsylvania School of Medicine, Philadelphia, PA, U.S.A.
authors.forename: C O
authors.initials: CO
authors.lastname: Anyanwu
authors.affiliation: Division of Immunology and Rheumatology, Department of Dermatology and Medicine, Stanford University School of Medicine, Stanford, CA, U.S.A.
authors.forename: D F
authors.initials: DF
authors.lastname: Fiorentino
authors.affiliation: Division of Immunology and Rheumatology, Department of Dermatology and Medicine, Stanford University School of Medicine, Stanford, CA, U.S.A.
authors.forename: L
authors.initials: L
authors.lastname: Chung
authors.affiliation: Division of Immunology and Rheumatology, Department of Dermatology and Medicine, Stanford University School of Medicine, Stanford, CA, U.S.A.
authors.forename: C
authors.initials: C
authors.lastname: Dzuong
authors.affiliation: Department of Biostatistics and Epidemiology, University of Pennsylvania, Philadelphia, PA, U.S.A.
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Dermatology, University of Pennsylvania School of Medicine, Philadelphia, PA, U.S.A.
authors.forename: J
authors.initials: J
authors.lastname: Okawa
authors.affiliation: Department of Dermatology, University of Pennsylvania School of Medicine, Philadelphia, PA, U.S.A.
authors.forename: K
authors.initials: K
authors.lastname: Carr
authors.affiliation: Department of Biostatistics and Epidemiology, University of Pennsylvania, Philadelphia, PA, U.S.A.
authors.forename: K J
authors.initials: KJ
authors.lastname: Propert
authors.affiliation: Philadelphia Veterans Affairs Medical Center, Philadelphia, PA, U.S.A.|Department of Dermatology, University of Pennsylvania School of Medicine, Philadelphia, PA, U.S.A.
authors.forename: V P
authors.initials: VP
authors.lastname: Werth
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003882:Dermatomyositis / Q000473:pathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D012372:ROC Curve; D012720:Severity of Illness Index; D064232:Visual Analog Scale; D055815:Young Adult