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Reporting of eligibility criteria of randomised trials: cohort study comparing trial protocols with subsequent articles

BMJ 2011; 342 doi: (Published 05 April 2011) Cite this as: BMJ 2011;342:d1828
  1. Anette Blümle, research fellow1,
  2. Joerg J Meerpohl, research fellow12,
  3. Gerta Rücker, research fellow1,
  4. Gerd Antes, director1,
  5. Martin Schumacher, director1,
  6. Erik von Elm, senior researcher13
  1. 1German Cochrane Center, Department of Medical Biometry and Statistics, Institute of Medical Biometry and Medical Informatics, University Medical Center Freiburg, Berliner Allee 29, 79110 Freiburg, Germany
  2. 2Division of Pediatric Hematology and Oncology, Department of Pediatrics, University Medical Center Freiburg, Germany
  3. 3Swiss Paraplegic Research, Nottwil, Switzerland
  1. Correspondence to: A Blümle bluemle{at}
  • Accepted 9 January 2011


Objective To determine whether and how eligibility criteria of participants prespecified in protocols of randomised trials are reported in subsequent articles.

Design Cohort study.

Setting Protocols submitted to the ethics committee of a German medical faculty.

Data sources 52 trial protocols and 78 subsequent publications published between 2000 and 2006.

Main outcome measure Proportion of matching, missing, modified, or newly added eligibility criteria between trial protocols and subsequent publications.

Results Differences were found between protocols and subsequent publications for all 52 trials. Information on eligibility criteria was missing in the publications for all 52 trials (100%, 95% confidence interval 93% to 100%), modified for 44 (85%, 72% to 93%), and newly added for 21 (41%, 27% to 55%). The mean number of eligibility criteria for each trial was 25 (range 7-43) and the mean proportion of matching eligibility criteria per trial was 50% (95% confidence interval 44% to 55%, range 13-93). Of 1248 eligibility criteria prespecified in the protocols, 606 (49%, 46% to 51%) were matching in subsequent publications, 479 (38%, 36% to 41%) were missing, and 163 (13%, 11% to 15%) were modified. 51 eligibility criteria were added to publications. Most prespecified eligibility criteria were about comorbidity (42%, 39% to 45%), treatment (20%, 18% to 22%), or type or severity of illness (17%, 15% to 19%). Most of the missing eligibility criteria (96%, 94% to 97%) and modified eligibility criteria (54%, 46% to 62%) suggested broader study populations and most of the added eligibility criteria (86%, 74% to 94%) suggested narrower study populations.

Conclusions Many users of trial information rely on published journal articles. These articles generally do not reflect the exact definition of the study population as prespecified in the protocol. Incomplete or inadequate reporting of eligibility criteria hampers a proper assessment of the applicability of trial results.


  • We thank the University of Freiburg’s research ethics committee for access to its files and cooperation and Julia Lindenberg for help with data extraction.

  • Contributors: All authors contributed to the study concept and design, data analysis, and interpretation. AB is guarantor; she had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. AB and EvE drafted the manuscript.

  • Funding: This study was funded by the German Research Foundation (DFG) (EL 544/1-1). The funder had no role in the design and conduct of the study, data collection and analysis, interpretation of the data, writing of the manuscript, and decision to submit the manuscript for publication.

  • Competing interests: All authors have completed the Unified Competing Interest form at (available on request from the corresponding author) and declare: AB was supported by the German Research Foundation (DFG) (EL 544/1-1); no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: The University of Freiburg’s research ethics committee approved access to all study protocols submitted in 2000, including amendments, progress reports, and correspondence. Ethical approval for the research was not required.

  • Data sharing: No additional data available.

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