Framing the numerical findings of Cochrane plain language summaries: two randomized controlled trials.

Background: Cochrane systematic review Plain language Summaries (CSR PLSs should serve as a tool for the evidence translation to non-medical population. However, the evidence of optimal type of numerical presentation in CSR PLSs is still scarce. The aim of this study was to investigate readers' comprehension and preferences for different presentation of findings, including framing and numerical data, in Cochrane systematic review Plain Language Summaries (CSR PLSs).

Methods: We conducted a parallel randomized trial and a crossover randomized trial at the School of Medicine and family practice offices in Split, Croatia. The participants were students and consumers. We assessed possible differences in comprehension, measured by four questions on PLS content, of CSR PLSs depending on the positive or negative framing of results (n = 91) (Trial 1) or using percentages or frequencies for the presentation of results (n = 245) (Trial 2). The outcome measures were comprehension of PLS content, perceived effectiveness of the treatment and readiness to use the treatment (all on 1-10 scales).

Results: In Trial 1 we found no difference in readers' perception of the effectiveness of the described treatment, desire that the treatment be offered by their family doctor, readiness to use the treatment, or comprehension when CSR PLS results were presented positively or negatively. In Trial 2 we found no difference in CSR PLS comprehension when results were presented as natural frequencies or percentages (BF = 0.62, Bayesian t-test for independent samples).

Conclusions: Numerical presentation and framing direction of results appear to have no significant impact on understanding of messages in CSR PLSs.

Trial Registration: The trials were registered in ClinicalTrials.gov. Protocol registration numbers: Trial 1: NCT03442387; Trial 2: NCT03554252.