Consumer involvement in consent document development: a multicenter cluster randomized trial to assess study participants' understanding

Background: Despite widespread agreement on the importance of informed consent in clinical research, uncertainty remains about the adequacy of current consent procedures and documentation. Methods: The objective of the study was to compare an informed consent document developed by a consumer group of potential study participants to one developed by the study investigators. The study was a cluster randomized, controlled study embedded in a 'parent' randomized controlled trial of 1092 participants with Gulf War veterans' illnesses recruited in 1999-2000 at 20 US medical centers. Centers were randomized to the investigator-developed or participant-developed consent document. The primary outcome measure was an Informed Consent Questionnaire-4 (ICQ-4), a validated four-item scale measuring self-reported participant understanding scored from 0 to 1. Secondary outcomes included the Client Satisfaction Questionnaire-8 and measures of study refusal and adherence to the parent trial protocol. Results: There were no significant differences between consent documents on the ICQ-4 score overall or at any of the time points. Mean (95% CI) treatment differences ranged from +0.020 (-0.015, 0.055) (better understanding) at entry to -0.021 (-0.054, 0.012) (worse understanding) at three-months for the participant versus the investigator document group. There were also no significant differences in satisfaction, adherence to the protocol, or in the proportion of patients who refused to participate in the trial. Limitations The consumer group may not have been representative of the study participants and they did not suggest dramatic changes to the consent document. The outcome assessment questionnaire was not validated prior to the trial's initiation. Conclusions: Consumer modification of the consent document did not lead to either benefit or harm in understanding, satisfaction, or study refusal and adherence rates. This study did demonstrate, however, that embedding consent studies in a clinical trial is feasible and can address important questions about informed consent without disrupting the primary study.