Available data suggest that prospective research participants may frequently
not understand information disclosed to them in the informed consent process.
Little is known about how understanding can be improved.
To review research on interventions to improve research participants’
understanding of information disclosed in the informed consent process.
Data Sources and Study Selection
A search of MEDLINE was performed using the terms informed consent and clinical research and informed
consent and (comprehension or understanding) from 1966 to March 2004
, which included randomized controlled trials, longitudinal trials, and controlled
trials with nonrandom allocation that compared the understanding of research
participants who had undergone only a standard informed consent process to
that of participants who had received an intervention to improve their understanding.
A comprehensive bibliography of empirical research on informed consent published
in January 1999 was also reviewed, as were personal files and all issues of
the journals IRB and Controlled
Study design, quality criteria, population characteristics, interventions,
and outcomes for each trial were extracted. The statistical significance of
the interventions’ effects on understanding were noted, as were mean
scores for understanding for each group of each trial. For those trials that
measured the secondary outcomes of satisfaction and willingness to enroll,
results were also summarized.
Thirty studies described 42 trials that met inclusion criteria. Of 12
trials of multimedia interventions, 3 showed significant improvement in understanding.
Of 15 trials of enhanced consent forms, 6 showed significant improvement in
understanding (all P<.05), but 5 of 6 trials were
of limited quality, casting doubt on their practical relevance. Of 5 trials
of extended discussion, 3 showed significant improvement in understanding
(all P<.001) and 2 showed trends toward improvement
(P=.054 and P=.08). Of 5
trials of test/feedback, all showed significant improvement in understanding
(all P<.05) but were flawed in that they may have
mistaken rote memorization for improvement in understanding. Another 5 trials
were put into a miscellaneous category and had varying impact on understanding.
Some demographic factors, particularly lower education, were associated with
less understanding. Satisfaction and willingness to enroll were never significantly
diminished by an intervention .
Efforts to improve understanding through the use of multimedia and enhanced
consent forms have had only limited success. Having a study team member or
a neutral educator spend more time talking one-on-one to study participants
appears to be the most effective available way of improving research participants’
understanding; however, further research is needed.