Bias from requiring explicit consent from all participants in observational research: prospective, population based study

Abstract

Objective To evaluate the differences between adults who consent to participate in observational research, and those who do not. Design Prospective, population based cohort study. Setting Primary and secondary care throughout Scotland. Participants 187 adults (aged ≥ 16 years) resident in Scotland at the time of their first diagnosis of a brain arteriovenous malformation in 1999-2002. Intervention Postal consent form sent via participants' general practitioner. Main outcome measures Differences between consenters and non-consenters in demographic and clinical features at first presentation, and outcome during follow-up. Results 111 adults (59%) consented to participate in the study. These consenters were not significantly different from non-consenters in age, sex, or socioeconomic status at first presentation. However, consenters were significantly more likely than non-consenters to present alive and independent, and with a seizure. During follow-up, consenters were significantly more likely to receive interventional treatment. Although consenters' survival was significantly better, they were more likely to have a seizure during follow-up. Presentation with intracranial haemorrhage conferred a higher risk of subsequent haemorrhage when the whole cohort was analysed, but not when it was restricted to consenters. Conclusions We have found differences between adults who consent to participate in observational records-based research and those who do not, or cannot, consent. Blanket requirements for explicit consent for the use of individuals' identifiable data can bias disease registers, epidemiological studies, and health services research.

Ethical Issues in Cardiovascular Research Involving Humans

“…In Scotland it was demonstrated that bias was introduced in requiring explicit consent for use of medical records in an observational population-based study of brain arteriovenous malformations. 70 Similar experience has been reported in studies of ischemic heart disease. 71,72 Annas 73 notes the reality of wide variation in institutional review board decisions regulating use of data from medical records.…”

Predictors of Adolescents’ Consent to Use Health Records for Research and Results from Data Collection in a Swedish Twin Cohort

“…When the choice to consent is dependent on characteristics pertaining to the individual or context, the selection of participants for the study is consequently non-random, which introduces the possibility of bias in estimations of associations within the sample (Groenwold et al, 2013;Hernan et al, 2004) It has previously been demonstrated that individuals who consent to medical research participation may be different in several ways from those who decline participation, but consistent patterns are lacking (Kho et al, 2009). For example, several studies have shown that males were more likely to consent (Damery et al, 2011;Knies et al, 2012; Twins' Consent to Research Using Health Records Matsui et al, 2005;Schwartz et al, 2005;Woolf et al, 2000), whereas others have not demonstrated any sex difference in consent rates (Al-Shahi et al, 2005;Baker et al, 2000;Beebe et al, 2011;Buckley et al, 2007;Huang et al, 2007;Klassen et al, 2005;McKinney et al, 2005) and some have seen a higher likelihood of consent among females (Dunn et al, 2004;Kho et al, 2009). The age of the potential study participants may play a part in the choice to consent.…”

Recruiting individuals into the HTLV cohort study in the United Kingdom: clinical findings and challenges in the first six years, 2003 to 2009

“…In our study, a relatively large number of participants reported having had arthritis, although without a suitable control group, it is not possible to say whether this was associated with HTLV infection or not. A number of studies have also found associations between HTLV and uveitis [3], tuberculosis [26] and thyroiditis [27], but few HTLV National Register participants reported these conditions. Blood donor recruitment was higher during prospective recruitment, which suggests that active recruitment of blood donors during their post-test discussion with blood service staff presents the best opportunity to discuss participation and obtain consent.…”