Context: The quality of a process can only be tested against its agreed objectives. Editorial peer-review is widely used, yet there appears to be little agreement about how to measure its effects or processes.
Methods: To identify outcome measures used to assess editorial peer review as performed by biomedical journals, we analyzed studies identified from 2 systematic reviews that measured the effects of editorial peer review on the quality of the output (ie, published articles) or of the process itself (eg, reviewers' comments).
Results: Ten studies used a variety of instruments to assess the quality of articles that had undergone peer review. Only 1, nonrandomized study compared the quality of articles published in peer-reviewed and non-peer-reviewed journals. The others measured the effects of variations in the peer-review process or used a before-and-after design to measure the effects of standard peer review on accepted articles. Eighteen studies measured the quality of reviewers' reports under different conditions such as blinding or after training. One study compared the time and cost of different review processes.
Conclusions: Until we have properly defined the objectives of peer-review, it will remain almost impossible to assess or improve its effectiveness. The research needed to understand the broader effects of peer review poses many methodologic problems and would require the cooperation of many parts of the scientific community.