Consent bias may reduce value of observational research

Consent bias may reduce value of observational research


By Liam Davenport

05 September 2007

Heart 2007; 93: 1116-1120


MedWire News: Consent bias may impact on observational research into ischemic heart disease, with clinically important prognostic variables associated with consent preferences, say Irish researchers.


Patients' right to privacy and confidentiality has been increasingly acknowledged in recent years. Although the implications of prior written consent have been discussed in terms of healthcare professionals, public attitudes have not been widely examined, and what research has been conducted has yielded mixed results.


Researchers have expressed concerns over the potential constraints of strict consent rules on observational research, so Brian Buckley, from the National University of Ireland in Galway, and colleagues sought to determine differences between adults who consent to participating in such research and those who do not.


They examined data on a representative cohort of 1609 patients with ischemic heart disease from 35 randomized general practices identified in 2001. Baseline questionnaires were sent to 1269 participants, with follow-up medical charts up to the years 2005-2006 located for 1592 patients.


In all, 876 (69%) of the questionnaires were returned completed. Of these, 574 (65.5%) gave consent for their participation in further research, the team reports in the journal Heart.


Multiple logistic regression analysis revealed that patients were more likely to consent to participation in further research if the factors they had undergone prior percutaneous transluminal coronary angioplasty, a last recorded blood pressure of less than 140/90 mmHg, a last recorded total cholesterol level of less than 5 mmol/l, and were an ex-smoker, as opposed to a current or non-smoker, at respective odds ratios of 1.77, 1.45, 1.71, and 1.73.


The team says: "The implication is that if cohorts in the future are dependent upon prior written consent they are likely to contain disproportionate numbers of those who have made healthy lifestyle decisions, who have previously benefited from healthcare, or those whose clinical risk factors are already well managed.

"This may have two serious consequences: first, the generalizability of observational research will be reduced; second, the effects of treatments may be variously overestimated or underestimated if those who are most unwell or are not making healthy lifestyle decisions are under-represented in study populations."


In an accompanying editorial, Cornelia Junghans and Melvyn Jones, from Royal Free and University College London Medical School in the UK, write: "Possibly, the public may decide that individual privacy is more important than the societal benefits of research, once an open debate has taken place.


"In this case, patient education may be the only way forward to ensure adequate and unbiased participation in research."


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