title: Categorization of Skindex-29 scores using mixture analysis.
abstract: BACKGROUND
  Although the Skindex-29 is among the most commonly used health-related quality of life instruments in dermatology, the interpretation of obtained scores is not well documented.
  
  
  OBJECTIVE
  To create categories of the scores of the Skindex-29.
  
  
  METHODS
  The Skindex-29 scores of454 Italian patients with 6 distinct skin diseases from a specialized center were analyzed using mixture analyses. The validity of the obtained categorizations was tested.
  
  
  RESULTS
  Mixture analysis showed 4 distinct components (categories) for the emotion and functioning scale and 5 for the symptom scale. The total Skindex-29 score was categorized into 4 levels. As expected, patients with inflammatory diseases had higher levels of impairment, those with vitiligo and alopecia areata had low symptom levels and those with nevi were predominantly located in the lower categories for each of the scales.
  
  
  CONCLUSIONS
  The proposed categories of the Skindex-29 may ease the interpretation of obtained continuous scores.
authors.affiliation: Department of Dermatology, Erasmus MC, Rotterdam, The Netherlands.
authors.forename: Tamar
authors.initials: T
authors.lastname: Nijsten
authors.forename: Francesca
authors.initials: F
authors.lastname: Sampogna
authors.forename: Damiano
authors.initials: D
authors.lastname: Abeni
mesh_terms: D000152:Acne Vulgaris / Q000523:psychology; D000506:Alopecia Areata / Q000523:psychology; D012628:Dermatitis, Seborrheic / Q000523:psychology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009506:Nevus / Q000523:psychology; D011565:Psoriasis / Q000523:psychology; D011594:Psychometrics / Q000379:methods*; D011788:Quality of Life; D015203:Reproducibility of Results; D012871:Skin Diseases / Q000523:psychology*; D011795:Surveys and Questionnaires; D014820:Vitiligo / Q000523:psychology