Background. Patient comprehension is fundamental to valid informed consent. Current practices often result in inadequate patient comprehension. Purpose. An updated review to evaluate the characteristics and outcomes of interventions to improve patient comprehension in clinical informed consent. Data Sources. Systematic searches of MEDLINE and EMBASE (2008-2018). Study Selection. We included randomized and nonrandomized controlled trials evaluating interventions to improve patient comprehension in clinical informed consent. Data Extraction. Reviewers independently abstracted data using a standardized form, comparing all results and resolving disagreements by consensus. Data Synthesis. Fifty-two studies of 60 interventions met inclusion criteria. Compared with standard informed consent, a statistically significant improvement in patient comprehension was seen with 43% (6/14) of written interventions, 56% (15/27) of audiovisual interventions, 67% (2/3) of multicomponent interventions, 85% (11/13) of interactive digital interventions, and 100% (3/3) of verbal discussion with test/feedback or teach-back interventions. Eighty-five percent of studies (44/52) evaluated patients' understanding of risks, 69% (41/52) general knowledge about the procedure, 35% (18/52) understanding of benefits, and 31% (16/52) understanding of alternatives. Participants' education level was reported heterogeneously, and only 8% (4/52) of studies examined effects according to health literacy. Most studies (79%, 41/52) did not specify participants' race/ethnicity. Limitations. Variation in interventions and outcome measures precluded conduct of a meta-analysis or calculation of mean effect size. Control group processes were variable and inconsistently characterized. Nearly half of studies (44%, 23/52) had a high risk of bias for the patient comprehension outcome. Conclusions. Interventions to improve patient comprehension in informed consent are heterogeneous. Interactive interventions, particularly with test/feedback or teach-back components, appear superior. Future research should emphasize all key elements of informed consent and explore effects among vulnerable populations.
Keywords: comprehension; informed consent; interpersonal communication; intervention; understanding.