Clinical practice and public health policy decisions depend on high-quality information about research findings. However, growing evidence shows widespread deficiencies in the reporting of health research studies. Problematic issues include (but are not limited to) non-reporting or delayed reporting of entire studies;1 omission of crucial information in the description of research methods2 and interventions;3 selective reporting of only some outcomes;4 presenting data and graphs in confusing and misleading ways;5 and omissions from or misinterpretation of results in abstracts.6 These deficiencies have serious consequences for clinical practice, research, policy making, and ultimately for patients.

We illustrate the seriousness of the problem with several examples. In 1999, Drummond Rennie highlighted several systematic reviews7 8 9 that had identified multiple non-transparent publications of the same trials; this publication bias artificially created an impression of much larger support for the efficacy of studied interventions.10 More recently, Dwan et al summarised the evidence from 16 cohort studies that assessed study publication bias and outcome reporting bias in randomised controlled trials.4 Studies reporting positive or significant results were more likely to be published, and outcomes that were statistically significant were more likely to be fully reported. Also, discrepancies between the publications and original protocols were common: 40–62% of studies had at least 1 primary outcome that was changed, newly introduced, or omitted. Chan and Altman2 assessed reporting of methodological information in 519 randomised trials published in 2000. Fewer than half included an adequate description of the sample size calculation, primary outcomes, random sequence generation, allocation concealment, and handling of attrition (all of which are crucial to assess the validity of trial findings).

Evidence is accumulating that use of reporting guidelines can improve the completeness and transparency of publications.11 12 Reporting guidelines specify a minimum set …