The citation of relevant systematic reviews and randomised trials in published reports of trial protocols

It is important that planned randomised trials are justified and placed in the context of the available evidence. The SPIRIT guidelines for reporting clinical trial protocols recommend that a recent and relevant systematic review should be included. The aim of this study was to assess the use of the existing evidence in order to justify trial conduct.

Protocols of randomised trials published over a 1-month period (December 2015) indexed in PubMed were obtained. Data on trial characteristics relating to location, design, funding, conflict of interest and type of evidence included for trial justification was extracted in duplicate and independently by two investigators. The frequency of citation of previous research including relevant systematic reviews and randomised trials was assessed.

Overall, 101 protocols for RCTs were identified. Most proposed trials were parallel-group (n = 74; 73.3%). Reference to an earlier systematic review with additional randomised trials was found in 9.9% (n = 10) of protocols and without additional trials in 30.7% (n = 31), while reference was made to randomised trials in isolation in 21.8% (n = 22). Explicit justification for the proposed randomised trial on the basis of being the first to address the research question was made in 17.8% (n = 18) of protocols. A randomised controlled trial was not cited in 10.9% (95% CI: 5.6, 18.7) (n = 11), while in 8.9% (95% CI: 4.2, 16.2) (n = 9) of the protocols a systematic review was cited but did not inform trial design.

A relatively high percentage of protocols of randomised trials involves prior citation of randomised trials, systematic reviews or both. However, improvements are required to ensure that it is explicit that clinical trials are justified and shaped by contemporary best evidence.