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Table 1 Studies included in the review of patients understanding of informed consent in clinical trials

From: The reality of informed consent: empirical studies on patient comprehension—systematic review

Author [year] Country Number of patients Age Subject of the study Population Timing Aspects of IC explored in the study and percentage of correct answers Level of education
Ponzio [6] [2018] Italy 60 52.9 ± 11.7 Neurology Adult patients ND Purpose of the study 20.7–93.5%
Blindness 58.6–89.7%
Freedom to withdrawal 100%
Confidentiality 29–93.1%
Risk 6.9–100%
Benefits 34.5–96.6%
ND
Schumacher [7] [2017] USA 50 61 (35–85) Oncology Adult patients Mean time 60 ± 51
Days after ICP for treatment (oncology) trial
Risk 20%
Direct benefits 76%
Freedom to withdrawal 90%
Voluntary participation 90%
Less than high school diploma 9%
High school diploma 41%
Associate degree 13%
Bachelor’s degree 26%
Master’s degree or higher 11%
Chu [8] [2012] Republic of Korea 291 36.4 ± 15.0 Oncology
Cardiology
Endocrinology
Gastroenterology
Immunology
Neurology
Others
Adult patients ND Freedom to withdrawal 78.2%
Compensation 43.4%
Randomisation 49.8%
Fulfilling inclusion criteria to be eligible 82.5%
Approval of bioethics committee 78.7%
Voluntary participation 53.6%
≤ High school 28.9%
≥ College 71.1%
Chaisson [9] [2011] Botswana 1835 33 Infectious disease Adult patients Within 30 days after ICP Purpose of the study 90–97%
Placebo and blinding 64–65%
Voluntary participation 69–77%
Risk 87–94%
Freedom to withdrawal 76–77%
No formal education 7%
Primary school 28%
Secondary school 59%
Tertiary 9%
Ellis [10] [2010] USA/Mali 171
89
700
30 (18–50)
27 (18–50)
ND
Infectious disease (malaria vaccine) Adult patients and parents or guardians Directly after ICP Freedom to withdrawal 93–98%1
Safety and side effects 48–85%1
ND
Minnies [6] [2008] South Africa 192 26 (16–44) Infectious disease Parents or guardians Within 1 h after ICP Reason to participate 85.4%
Purpose of the study 80.6%
Procedures 60.9%
Duration of the study 66.3%
Risks 79.2%
Benefits 51.3%
Voluntary participation 65.1%
Confidentiality 73.3%
Storage and use 82.9%
Grade ≤ 6 23.4%
Grade 7–11 42.8%
Grade ≥ 12 33.9%
Bergenmar [11] [2008] Sweden 282 60 (32–82) Oncology Adult patients Within max. 2 weeks after ICP Voluntary participation mean 96.2 (13.2)
Confidentiality mean 84.3 (26.2)
Potential risks or discomfort mean 76.7 (28.2)
Withdrawal criteria > 90%
Randomisation > 80%
Side effects > 10%
Compulsory school (1–9 years) 24%
Senior high school (10–12 years) 29%
University education (13–16 years) 38%
Higher university education (> 16 years) 9%
Bertoli [12] [2007] Argentina 105 56.3 ± 11.8 Rheumatology Adult patients ND Participant’s blinding 64.9%
Investigator’s blinding 27.3%
Freedom to withdrawal 77.8% Randomisation 10%
Placebo 47–65.5%2
Confidentiality 52%
Illiterate 1.9%
Elementary school (7 years of education) 48.6%
High school 28.6%
Higher educational degrees 19.0%
Krosin [13] [2006] Mali 163 ND Infectious disease (malaria vaccine) Adult patients Within 2 days after ICP Voluntary participation 57%
Compensation 44%
Withdrawal criteria 10%
Withdrawal consequences 44%
Randomisation and placebo 68%
Side effects 7%
Lay scientific knowledge 73%
Primary education 67%
Literate to some degree 70%
Criscione [14] [2003] USA 30 44.9 ± 9.8 Rheumatology Adult patients 7–28 days after ICP Voluntary participation 77%
Freedom to withdrawal 63%
Participant’s blinding 53%
Investigator’s blinding 80%
Randomisation 50%
Placebo 87%
Risk and safety 30%
Years of education, median 12.5
Pope [15] [2003] Canada 190 63 (22–84) Cardiology, ophthalmology, rheumatology Adult patients 2 months to 5 years after ICP Participant’s blinding 14–47%3
Investigator’s blinding 9–60%3
Randomisation 20–66%3
Placebo 13–49% 3
Elementary school 18%
High school 45%
Higher education 36%
McNally [16] [2001] UK 29 32 Infectious disease Parents or guardians ND Randomisation 75%
Blinding 75%
Placebo 64%
No formal education 18%
≥ Advanced “A” level 21%
Ordinary “O” level 39% National vocational qualification 11%
Certificate of secondary education 11%
Itoh [17] [1997] Japan 32 58 (30–68) Oncology Adult patients After ICP before drug treatment Freedom to withdrawal 97% Right to therapeutic choice 88% Elementary school 16%
High school 47%
Higher education 28%
Unknown 9%
Harrison [18] [1995] USA 175 37 (18–56) Infectious disease (HIV vaccine) Adult patients Before ICP Confidentiality 95–100%4
Side effects 83–100%4
Randomisation 68–96% 4
ND
  1. ND no data, ICP informed consent process
  2. 1Depending on population Mali parents/guardians of child participants vs USA adult participants
  3. 2Depending on the trial
  4. 3Depending on the treatment study: cardiology, ophthalmology, rheumatology
  5. 4Depending on subgroup: eligible and ineligible for the vaccine trial, and then further divided into injection drug users (IDU) and others within each group