BackgroundLectures with slide presentations are widely used to teach evidence-based medicine to large groups. Take-home messages (THMs) are poorly identified and recollected by students. We investigated whether an instruction to list THMs in written form on slides would improve the retention thereof by residents, and the residents’ level of knowledge, 1 month after lectures.MethodsProspective blinded randomized controlled study was conducted. Twelve lectures (6 control and 6 intervention lectures) were delivered to 73 residents. For the intervention lectures, the lecturers were instructed to incorporate clear written THMs into their slide presentations. The outcomes were ability of resident to recollect THMs delivered during a lecture (as assessed by accordance rate between the lecturers’ and residents’ THMs) and knowledge (as assessed by multiple choice questions (MCQs)).ResultsData for 3738 residents’ THMs and 3410 MCQs were analyzed. The intervention did not significantly increase the number of THMs written on slides (77% (n = 20/26), 95% CI 56–91 vs 64% (n = 18/28), 95% CI 44–81, p = 0.31) nor THMs retention (13% (n = 238/1791), 95% CI 12–15 vs 17% (n = 326/1947), 95% 15–18, p = 0.40) nor knowledge (63.8 ± 26.2 vs 61.1 ± 31.4 /100 points, p = 0.75). In multivariable analyses performed with all THMs written on slides from the two groups, a superior knowledge was associated with notetaking during lectures (OR 1.88, 95% CI 1.41–2.51) and THMs retention (OR 2.17, 95% CI 1.54–3.04); and THMs retention was associated with written THMs (OR 2.94, 95% CI 2.20–3.93).ConclusionsIn lectures delivered to residents, a third of the THMs were not in written form. An intervention based on an explicit instruction to lecturers to provide THMs in written form in their slide presentations did not result in increased use of written THMs into the slide presentation or improvement of the THMs retention or level of knowledge. However, we showed that there was a strong positive association between writing THMs on a slide, retention of THMs and residents’ knowledge. Further researches are needed to assess interventions to increase written THMs in lectures by faculty.Trial registrationClinicalTrials.gov NCT01795651 (Fev 21, 2013).