title: Objective measurements of erythema, elasticity and scale could overcome the inter- and intra-observer variations of subjective evaluations for psoriasis severity.
abstract: BACKGROUND
  Most conventional subjective assessments for psoriasis have inevitable inter- and intra-observer variations.
  
  
  OBJECTIVE
  We investigated the objective bioengineering parameters of color and mechanical properties which are possible substitutes of the erythema, scale, and thickness scores of psoriatic plaque.
  
  
  METHODS
  Age, gender, and Psoriasis Severity Index (PSI) were noted. In addition, bioengineering parameters of color, mechanical properties, and scale were obtained.
  
  
  RESULTS
  The most prominently correlated bioengineering parameters were hue (tan(-1) b*/a*), desquamation index (DI), and elasticity (R7) for PSI erythema, scale, and thickness, respectively. These parameters not only showed significant differences between lesion and control groups but also changed according to psoriasis severity scores. We also showed that brighter, scaly lesions had lower elasticity while the more erythemic lesions corresponded to a more fluid-like state.
  
  
  CONCLUSIONS
  We found that three bioengineering parameters are potential candidates for an objective Psoriasis Severity Index (oPSI).
authors.affiliation: Department of Dermatology, Seoul National University College of Medicine, Seoul National University Bundang Hospital, 166 Gumi-ro, Seongnam, Gyeonggi, 463-707, Korea.
authors.forename: Jae Woo
authors.initials: JW
authors.lastname: Choi
authors.forename: Soon Hyo
authors.initials: SH
authors.lastname: Kwon
authors.forename: Jai Il
authors.initials: JI
authors.lastname: Youn
authors.forename: Sang Woong
authors.initials: SW
authors.lastname: Youn
mesh_terms: D000328:Adult; D057005:Bioengineering; D003116:Color; D004548:Elasticity; D004890:Erythema / Q000150:complications; D005260:Female; D006801:Humans; D008297:Male; D015588:Observer Variation; D011565:Psoriasis / Q000150:complications / Q000473:pathology* / Q000503:physiopathology; D012720:Severity of Illness Index
keywords: bioengineering; objective assessment; psoriasis; psoriasis severity index; severity assessment