title: Levels of evidence in the voice literature.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the levels of evidence in the voice literature.
  
  
  METHODS
  Retrospective literature review.
  
  
  METHODS
  Retrospective review of all original articles published between January 2004 and December 2009 from four general otolaryngology journals and one subspecialty voice journal. All abstracts related to voice were evaluated and rated as to evidence-based medicine rating, graded levels A-D and 1a-5. Articles were also stratified by time over two consecutive 3-year intervals to assess changes over the time period.
  
  
  RESULTS
  Of the 6052 articles published, 950 (15.6%) were related to voice. Six hundred seventy-three articles (10.2%) were clinical articles, and 277 (4.6%) were basic science. Only 1% of the clinical articles were level A, 17% were level B, 73% were level C, and 9% were level D. No noticeable changes occurred in the levels of evidence over the interval of the first 3 years of the study in comparison to the last 3 years, although there was an increase in the number of basic science articles from 24.4% to 32.4%.
  
  
  CONCLUSIONS
  Despite strong recent interest in improving the quality of the evidence in the literature, the voice literature remains primarily level C and D with no appreciable change over the past 6 years.
authors.affiliation: Head and Neck Institute, The Cleveland Clinic, Cleveland, Ohio 44195, USA. benninm@ccf.org
authors.forename: Michael S
authors.initials: MS
authors.lastname: Benninger
mesh_terms: D055317:Evidence-Based Practice; D010506:Periodicals as Topic; D014831:Voice