title: Country development and manuscript selection bias: a review of published studies.
abstract: BACKGROUND
  Manuscript selection bias is the selective publication of manuscripts based on study characteristics other than quality indicators. One reason may be a perceived editorial bias against the researches from less-developed world. We aimed to compare the methodological quality and statistical appeal of trials from countries with different development status and to determine their association with the journal impact factors and language of publication.
  
  
  METHODS
  
  
  
  METHODS
  Based on the World Bank income criteria countries were divided into four groups. All records of clinical trials conducted in each income group during 1993 and 2003 were included if they contained abstract and study sample size.
  
  
  METHODS
  Cochrane Controlled Trials Register was searched and 50 articles selected from each income group using a systematic random sampling method in years 1993 and 2003 separately.
  
  
  METHODS
  Data were extracted by two reviewers on the language of publication, use of randomization, blinding, intention to treat analysis, study sample size and statistical significance. Disagreement was dealt with by consensus. Journal impact factors were obtained from the institute for scientific information.
  
  
  RESULTS
  Four hundred records were explored. Country income had an inverse linear association with the presence of randomization (chi2 for trend = 5.6, p = 0.02) and a direct association with the use of blinding (chi2 for trend = 6.9, p = 0.008); although in low income countries the probability of blinding was increased from 36% in 1993 to 46% in 2003. In 1993 the results of 68% of high income trials and 64.7% of other groups were statistically significant; but in 2003 they were 66% and 82% respectively. Study sample size and income were the only significant predictors of journal impact factor.
  
  
  CONCLUSIONS
  The impact of country development on manuscript selection bias is considerable and may be increasing over time. It seems that one reason may be more stringent implementation of the guidelines for improving the reporting quality of trials on developing world researchers. Another reason may be the presumptions of the researchers from developing world about the editorial bias against their nationality.
authors.affiliation: Center of Evidence Based Medicine, Tehran University of Medical Sciences, Shariati hospital, Kargar shomali Ave, Tehran, Iran. ryousefi@razi.tums.ac.ir
authors.forename: Reza
authors.initials: R
authors.lastname: Yousefi-Nooraie
authors.forename: Behnam
authors.initials: B
authors.lastname: Shakiba
authors.forename: Soroush
authors.initials: S
authors.lastname: Mortaz-Hejri
mesh_terms: D003906:Developing Countries / Q000191:economics*; D006801:Humans; D007182:Income / Q000145:classification / Q000706:statistics & numerical data; D016247:Information Storage and Retrieval; D016014:Linear Models; D008373:Manuscripts as Topic; D017712:Peer Review, Research; D010506:Periodicals as Topic / Q000706:statistics & numerical data*; D017594:Publication Bias; D016032:Randomized Controlled Trials as Topic / Q000592:standards*; D012107:Research Design; D014480:United Nations