title: A new classification system for grading the severity of onychomycosis: Onychomycosis Severity Index.
abstract: OBJECTIVE
  To establish and validate a new system to define the severity of onychomycosis. The Onychomycosis Severity Index (OSI) score is obtained by multiplying the score for the area of involvement (range, 0-5) by the score for the proximity of disease to the matrix (range, 1-5). Ten points are added for the presence of a longitudinal streak or a patch (dermatophytoma) or for greater than 2 mm of subungual hyperkeratosis. Mild onychomycosis corresponds to a score of 1 through 5; moderate, 6 through 15; and severe, 16 through 35.
  
  
  METHODS
  Consensus conference.
  
  
  METHODS
  Teleconference.
  
  
  METHODS
  The consensus group included 5 dermatologists, 1 dermatology resident with an interest in nail disorders, and a statistician. The meetings were held by closed teleconference.
  
  
  METHODS
  Index reliability.
  
  
  RESULTS
  The reliability of the OSI system was assessed in 2 steps. The first assessment included 37 dermatologists who scored 8 photographs of onychomycosis after being taught how to use the OSI. The scoring system showed very high reliability (Cronbach α = 0.99 and intraclass correlation coefficient [ICC] = 0.95). The second assessment entailed evaluation of 49 nails by 3 dermatologists, including an expert in the OSI. This assessment was conducted at the University of Alabama at Birmingham and at the Oregon Dermatology and Research Center, Portland. The scoring system showed very high reliabilities at both sites (Cronbach α = 0.99 and ICC = 0.96 at the University of Alabama at Birmingham, and Cronbach α = 0.98 and ICC = 0.93 at the Oregon Dermatology and Research Center).
  
  
  CONCLUSIONS
  The OSI is a new, simple, objective, reproducible numeric system to grade the severity of onychomycosis.
authors: Department of Dermatology, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
authors: Caitlin
authors: C
authors: Carney
authors: Antonella
authors: A
authors: Tosti
authors: Ralph
authors: R
authors: Daniel
authors: Richard
authors: R
authors: Scher
authors: Phoebe
authors: P
authors: Rich
authors: Jamie
authors: J
authors: DeCoster
authors: Boni
authors: B
authors: Elewski
mesh_terms: D005533:Foot Dermatoses / Q000145:classification / Q000175:diagnosis / Q000473:pathology*; D006801:Humans; D015588:Observer Variation; D014009:Onychomycosis / Q000145:classification / Q000175:diagnosis / Q000473:pathology*; D015203:Reproducibility of Results; D012720:Severity of Illness Index