Does the format of result presentation and type of conclusion in Cochrane plain language summaries matter? A randomised controlled trial.

Objectives: This study aimed to investigate whether the format and type of conclusion in Cochrane plain language summaries (PLSs) influence readers' perception of treatment benefit and decision-making.

Design: An online parallel group, three-arm randomised controlled trial was conducted.

Setting: The study was conducted online.

Participants: The participants were physiotherapy students.

Interventions: The participants read two Cochrane PLSs, one with a positive conclusion (strong evidence of benefit) and another with a negative conclusion (strong evidence of non-benefit). Each participant read the results of both reviews presented in one of three formats: (1) numerical, (2) textual or (3) numerical and textual.

Main outcome measures: The primary outcome measure was the participants' perception of treatment benefit.

Results: All three groups of participants perceived the treatment to have positive effects when the Cochrane PLS had a positive conclusion, regardless of the format of presentation (mean perception of treatment benefit score: textual 7.7 (SD 2.3), numerical 7.9 (SD 1.8), numerical and textual 7.7 (SD 1.7), p=0.362). However, when the Cochrane PLS had a negative conclusion, all three groups of participants failed to perceive a negative effect (mean perception of treatment benefit score: textual 5.5 (SD 3.3), numerical 5.6 (SD 2.7), numerical and textual 5.9 (SD 2.8), p=0.019).

Conclusions: The format of Cochrane PLSs does not appear to significantly impact physiotherapy students' perception of treatment benefit, understanding of evidence, persuasiveness or confidence in their decision. However, participants' perception of treatment benefit does not align with the conclusion when the Cochrane PLS indicates strong evidence of non-benefit from the intervention.

Trial registration number: CTRI/2022/10/046476.