Objective To conduct a systematic review and meta-analysis to assess the level of participants’ understanding of all components of informed consent in clinical trials.
Methods Relevant studies were identified by a search of PubMed, Scopus, Google Scholar, and manual approach with data up to October, 2013. The event rate was pooled using a random-effects model.
Findings One hundred and three studies evaluating 135 populations were included. Correct understanding of the freedom to withdraw from the study at any time, nature of study, voluntary nature of participation, understanding of benefit, purpose, awareness of potential risks and side effects, confidentiality, alternative treatment if withdrawn from the study, recognizing the comparator (treatment or placebo), and no therapeutic misconception, was noted in 75.8% (95% CI: 70.6-80.3), 74.7% (68.8-79.8), 74.7% (67.9-80.5), 74.0% (65.0-81.3), 69.6% (63.5-75.1), 67.0% (57.4-75.4), 66.2% (55.3-75.7), 64.1% (53.7-73.4), 62.9% (45.5-77.5), and 62.4% (50.1-73.2), respectively. The figures for comprehension of randomization, comprehension of placebo, and naming at least one risk were 52.1% (41.3-62.7), 53.3% (38.4-67.6), and 54.9% (43.3-65.0), respectively. Subgroup and meta-regression analyses identified some co-variates significantly affecting the results and revealed no change in the understanding of all components over a 30 – year period.
Conclusion: Mixed levels of correct understanding of components of informed consent were recorded in this meta-analysis. There is still much to be done to assist research participants achieve a comprehensive and complete understanding of informed consent, so that meaningful decision-making can be made and their best interest is protected.