Primary author contact for systematic reviews of randomized controlled trials: A systematic review

Systematic reviews (SRs) synthesize and evaluate data, mainly from randomized trials, which then guides the development of clinical recommendations in evidence-based medicine. However, the data and methodological information in the included papers can often be lacking or unclear, and reviewers usually need to contact the authors of included studies for clarifications. Contacting authors is recommended, but it is unclear how often SR teams do it, or what the level of response is.

To investigate how often reviewers undertake contact with the authors of included randomized controlled trials (RCTs) for clarification on data and risk of bias concerns, to explore the factors that influence whether SR authors contact or do not contact the authors, and the content and level of responses.

We conducted a systematic electronic database search in MEDLINE using the search string "(systematic review)" AND "(RCT OR randomized OR trial)" for articles published between 1 January 2024 and 19 February 2024, without language restrictions. Screening and data extraction was done independently by two reviewers, and conflicts resolved by a senior author. Contact authors of included SRs were contacted for clarifications.

Of the 329 included SRs, 38% (n = 125) explicitly mentioned contact with the authors of included studies. The remaining 62% (n = 204) did not. We attempted contact with all SR teams for clarifications and received 90 responses (19.4%). Of the 50 respondents who did not explicitly mention contact in their SRs, 25 (50%) replied that they did make contact. We received a total of 64 responses on the level and content of information sought. The mean ± SD contacts SR teams made were 10 (10), replies received 5 (6.7), and response waiting time 10.1 (28.3) weeks. Resources, time, poor previous experience, perceived likelihood of poor response and bias concerns were reported as barriers to attempting contact.

The majority of SRs published in 2024 did not confirm seeking clarifying or missing information from primary study authors. However, SR teams reported that 50% of contacted primary authors respond. Additional research can clarify this rate of response and establish methods to increase the integration of this core methodological element in SRs.