title: Validation of the Psoriasis Symptom Inventory (PSI), a patient-reported outcome measure to assess psoriasis symptom severity.
abstract: BACKGROUND
  The objective of this study was to evaluate the measurement properties of the Psoriasis Symptom Inventory (PSI), an eight-item patient-reported outcome measure for assessing severity of plaque psoriasis symptoms.
  
  
  METHODS
  In this prospective, randomized study using data from adults with moderate-to-severe plaque psoriasis, patients completed the PSI, Dermatology Life Quality Index (DLQI), SF-36v2 Acute, and Patient Global Assessment (PtGA). PSI construct validity was assessed using Spearman rank correlations between PSI and DLQI and SF-36; test-retest reliability and sensitivity to change were evaluated using PtGA as an anchor. Daily 24-h and weekly 7-day PSI versions were evaluated.
  
  
  RESULTS
  Eight US sites enrolled 143 patients; 139 (97.2%) completed the study. All symptoms (itch, redness, scaling, burning, cracking, stinging, flaking, and pain) were reported across all response options (not at all severe, mild, moderate, severe, very severe). Test-retest reliability was acceptable (intraclass correlation coefficients range = 0.70-0.80). A priori hypotheses of convergent and discriminant validity were confirmed by correlations of PSI with DLQI items and SF-36 domains. The PSI demonstrated good construct validity and was sensitive to within-subject change (p < 0.0001).
  
  
  CONCLUSIONS
  The PSI is brief, valid, reproducible, and responsive to change and has the potential to be a useful PRO measure in psoriasis clinical trials.
authors.affiliation: Health Research Associates, Inc., Mountlake Terrace, WA 98043, USA. bushnell@hrainc.net
authors.forename: Donald M
authors.initials: DM
authors.lastname: Bushnell
authors.forename: Mona L
authors.initials: ML
authors.lastname: Martin
authors.forename: Kelly
authors.initials: K
authors.lastname: McCarrier
authors.forename: Kenneth
authors.initials: K
authors.lastname: Gordon
authors.forename: Chiun-Fang
authors.initials: CF
authors.lastname: Chiou
authors.forename: Xingyue
authors.initials: X
authors.lastname: Huang
authors.forename: Brian
authors.initials: B
authors.lastname: Ortmeier
authors.forename: Gregory
authors.initials: G
authors.lastname: Kricorian
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D011446:Prospective Studies; D011565:Psoriasis / Q000175:diagnosis*; D057566:Self Report; D012720:Severity of Illness Index; D055815:Young Adult