title: Dissemination bias in systematic reviews of animal research: a systematic review.
abstract: BACKGROUND
  Systematic reviews of preclinical studies, in vivo animal experiments in particular, can influence clinical research and thus even clinical care. Dissemination bias, selective dissemination of positive or significant results, is one of the major threats to validity in systematic reviews also in the realm of animal studies. We conducted a systematic review to determine the number of published systematic reviews of animal studies until present, to investigate their methodological features especially with respect to assessment of dissemination bias, and to investigate the citation of preclinical systematic reviews on clinical research.
  
  
  METHODS
  Eligible studies for this systematic review constitute systematic reviews that summarize in vivo animal experiments whose results could be interpreted as applicable to clinical care. We systematically searched Ovid Medline, Embase, ToxNet, and ScienceDirect from 1st January 2009 to 9th January 2013 for eligible systematic reviews without language restrictions. Furthermore we included articles from two previous systematic reviews by Peters et al. and Korevaar et al.
  
  
  RESULTS
  The literature search and screening process resulted in 512 included full text articles. We found an increasing number of published preclinical systematic reviews over time. The methodological quality of preclinical systematic reviews was low. The majority of preclinical systematic reviews did not assess methodological quality of the included studies (71%), nor did they assess heterogeneity (81%) or dissemination bias (87%). Statistics quantifying the importance of clinical research citing systematic reviews of animal studies showed that clinical studies referred to the preclinical research mainly to justify their study or a future study (76%).
  
  
  CONCLUSIONS
  Preclinical systematic reviews may have an influence on clinical research but their methodological quality frequently remains low. Therefore, systematic reviews of animal research should be critically appraised before translating them to a clinical context.
authors.affiliation: Center for Pediatric Clinical Studies, University Children's Hospital Tuebingen, Tuebingen, Germany.
authors.forename: Katharina F
authors.initials: KF
authors.lastname: Mueller
authors.affiliation: Basel Institute for Clinical Epidemiology and Biostatistics, University Hospital Basel, Basel, Switzerland; Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Canada.
authors.forename: Matthias
authors.initials: M
authors.lastname: Briel
authors.affiliation: CELLS - Center for Ethics and Law in Life Sciences, University of Hannover, Hannover, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Strech
authors.affiliation: German Cochrane Centre, Medical Center - University of Freiburg, Freiburg, Germany.
authors.forename: Joerg J
authors.initials: JJ
authors.lastname: Meerpohl
authors.affiliation: German Cochrane Centre, Medical Center - University of Freiburg, Freiburg, Germany.
authors.forename: Britta
authors.initials: B
authors.lastname: Lang
authors.affiliation: Center for Medical Biometry and Medical Informatics, Medical Center - University of Freiburg, Freiburg, Germany.
authors.forename: Edith
authors.initials: E
authors.lastname: Motschall
authors.affiliation: Basel Institute for Clinical Epidemiology and Biostatistics, University Hospital Basel, Basel, Switzerland.
authors.forename: Viktoria
authors.initials: V
authors.lastname: Gloy
authors.affiliation: Clinical Research Centre Clinique du Centre Hospitalier Universitaire de Sherbrooke, Université de Sherbrooke, Sherbrooke, Canada.
authors.forename: Francois
authors.initials: F
authors.lastname: Lamontagne
authors.affiliation: Department of Neonatology, University Hospital Zuerich, Zuerich, Switzerland.
authors.forename: Dirk
authors.initials: D
authors.lastname: Bassler
mesh_terms: D000818:Animals; D004353:Drug Evaluation, Preclinical; D015201:Meta-Analysis as Topic; D017594:Publication Bias; D012196:Review Literature as Topic