title: A Systematic Review of Levels of Evidence in Auricular Defects Literature: How Far Has It Been During the Past Three Decades?
abstract: BACKGROUND
  Evidence-based medicine has been increasingly applied in clinical practice. The objective of this study was to identify the trends of levels of evidence and the relevant factors of higher level evidence in external auricular defects literature over 3 decades.
  
  
  METHODS
  The publications of external auricular defects published on 10 plastic surgery journals with higher impact factors from 1980 to 2011 were reviewed. Articles were appraised for level of evidence and other characteristics.
  
  
  RESULTS
  Of 245 eligible articles reviewed, no level I study was identified, 1 (0.41%) was level II, 10 (4.1%) were level III, 152 (62%) were level IV, 82 (33.5%) were level V. There was an increase of the levels of evidence (P ≈ 0) from 1980 to 2011. Studies with larger sample size (P = 0.014) and the application of P values or confidence intervals (P ≈ 0.000), those related to prevalence questions (P = 0.000004) were significantly associated with higher levels of evidence.
  
  
  CONCLUSIONS
  In the last 3 decades, the levels of evidence have increased significantly in external auricular defects literature. However, the predominant study remained levels IV and V.
authors.affiliation: Department of Plastic and Reconstructive Surgery, Shanghai 9th People's Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China.
authors.forename: Yiyuan
authors.initials: Y
authors.lastname: Li
authors.forename: Ruhong
authors.initials: R
authors.lastname: Zhang
authors.forename: Datao
authors.initials: D
authors.lastname: Li
mesh_terms: D015706:Bibliometrics; D004431:Ear, External / Q000002:abnormalities* / Q000601:surgery; D019317:Evidence-Based Medicine / Q000639:trends*; D006801:Humans; D019651:Plastic Surgery Procedures / Q000639:trends*; D018401:Sample Size