Protocol for a systematic review on the extent of non-publication of research studies and associated study characteristics

Abstract Background Methodological research has found that non-published studies often have different results than those that are published, a phenomenon known as publication bias. When results are not published, or are published selectively based on the direction or the strength of the findings, healthcare professionals and consumers of healthcare cannot base their decision-making on the full body of current evidence. Methods As part of the OPEN project (http://www.open-project.eu) we will conduct a systematic review with the following objectives: 1. To determine the proportion and/or rate of non-publication of studies by systematically reviewing methodological research projects that followed up a cohort of studies that a. received research ethics committee (REC) approval, b. were registered in trial registries, or c. were presented as abstracts at conferences. 2. To assess the association of study characteristics (for example, direction and/or strength of findings) with likelihood of full publication. To identify reports of relevant methodological research projects we will conduct electronic database searches, check reference lists, and contact experts. Published and unpublished projects will be included. The inclusion criteria are as follows: a. RECs: methodological research projects that examined the subsequent proportion and/or rate of publication of studies that received approval from RECs; b. Trial registries: methodological research projects that examine the subsequent proportion and/or rate of publication of studies registered in trial registries; c. Conference abstracts: methodological research projects that examine the subsequent proportion and/or rate of full publication of studies which were initially presented at conferences as abstracts. Primary outcomes: Proportion/rate of published studies; time to full publication (mean/median; cumulative publication rate by time). Secondary outcomes: Association of study characteristics with full publication. The different questions (a, b, and c) will be investigated separately. Data synthesis will involve a combination of descriptive and statistical summaries of the included methodological research projects. Discussion Results are expected to be publicly available in mid 2013.