title: Citation of previous meta-analyses on the same topic: a clue to perpetuation of incorrect methods?
abstract: CONCLUSIONS
  Systematic reviews and meta-analyses serve as a basis for decision-making and clinical practice guidelines and should be carried out using appropriate methodology to avoid incorrect inferences.
  
  
  OBJECTIVE
  We describe the characteristics, statistical methods used for meta-analyses, and citation patterns of all 21 glaucoma systematic reviews we identified pertaining to the effectiveness of prostaglandin analog eye drops in treating primary open-angle glaucoma, published between December 2000 and February 2012.
  
  
  METHODS
  We abstracted data, assessed whether appropriate statistical methods were applied in meta-analyses, and examined citation patterns of included reviews.
  
  
  RESULTS
  We identified two forms of problematic statistical analyses in 9 of the 21 systematic reviews examined. Except in 1 case, none of the 9 reviews that used incorrect statistical methods cited a previously published review that used appropriate methods. Reviews that used incorrect methods were cited 2.6 times more often than reviews that used appropriate statistical methods. We speculate that by emulating the statistical methodology of previous systematic reviews, systematic review authors may have perpetuated incorrect approaches to meta-analysis.
  
  
  CONCLUSIONS
  The use of incorrect statistical methods, perhaps through emulating methods described in previous research, calls conclusions of systematic reviews into question and may lead to inappropriate patient care. We urge systematic review authors and journal editors to seek the advice of experienced statisticians before undertaking or accepting for publication a systematic review and meta-analysis.
  
  
  BACKGROUND
  The author(s) have no proprietary or commercial interest in any materials discussed in this article.
authors.affiliation: Center for Clinical Trials, Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland 21205, USA. tli@jhsph.edu
authors.forename: Tianjing
authors.initials: T
authors.lastname: Li
authors.forename: Kay
authors.initials: K
authors.lastname: Dickersin
mesh_terms: D000959:Antihypertensive Agents / Q000627:therapeutic use; D001634:Bibliographies as Topic; D015706:Bibliometrics; D005902:Glaucoma, Open-Angle / Q000188:drug therapy; D006801:Humans; D007429:Intraocular Pressure / Q000187:drug effects; D015201:Meta-Analysis as Topic; D009885:Ophthalmology / Q000379:methods*; D011465:Prostaglandins, Synthetic / Q000627:therapeutic use; D012196:Review Literature as Topic; D013223:Statistics as Topic / Q000379:methods*
chemical_list: D000959:Antihypertensive Agents; D011465:Prostaglandins, Synthetic