Does Consent Bias Research?

Abstract

Researchers increasingly rely on large data sets of health information, often linked with biological specimens. In recent years, the argument has been made that obtaining informed consent for conducting records-based research is unduly burdensome and results in “consent bias.” As a type of selection bias, consent bias is said to exist when the group giving researchers access to their data differs from the group denying access. Therefore, to promote socially beneficial research, it is argued that consent should be unnecessary. After analyzing the biostatistics evidence and bioethics arguments, the article concludes that (1) claims about the amount of consent bias are overstated; (2) commonly used statistical methods usually can account for consent bias; and (3) any residual effects of consent bias are below an acceptable level of imprecision and constitute a reasonable social cost for conducting ethically responsible research.

Keywords:

• research
• selection bias
• consent bias
• and informed consent

Acknowledgments

The authors are indebted to the following individuals for helpful comments on an earlier draft: Rebecca Andridge, Kyle Brothers, Ellen Clayton, and Eric Meslin.

Notes

Throughout this article, we use odds ratios to summarize the association between two binary variables (e.g., blood donation and exercise). In this example, the odds ratio compares the odds (p/ (1 – p)) of exercising among blood donors to the odds of exercising among nondonors. An odds ratio of 1.00 indicates no association; an odds ratio less than 1 indicates smaller odds of exercising among blood donors; and an odds ratio greater than 1 indicates larger odds of exercising among blood donors.

The odds of consent among blood donors are 0.9/(1 – 0.9) = 9, and the odds of consent among nondonors are 0.7/(1 – 0.7) = 2.33, so the odds ratio comparing the odds of consent of donors to nondonors is 9/2.33 = 3.86.

Similarly, the odds of consent among those who exercise are 0.9/(1 – 0.9) = 9, and the odds of consent among those who did not exercise are 0.6/(1 – 0.6) = 1.5, so the odds ratio is 9/1.5 = 6.0.

In the first 5 months of its opt-out strategy, May 27, 2009, to November 2, 2009, of 240,000 newborns in Texas, the parents of 6,900 opted out. As of June 1, 2012, Texas law mandates opt-in consent for the release of individually identifiable newborn screening blood spots for research (Texas H.B. 411 2012).