While it may seem intuitive that a system of presumed consent for organ donation, where an individual is considered an organ donor unless he or she has expressly stated otherwise, would lead to higher rates of transplantation than one that requires an explicit indication of the wish to donate, the story is not so simple.
Nations that use presumed consent do have higher rates of deceased-donor kidney transplantation, but their rates of living-donor kidney transplantation are lower, reported an observational study published in Annals of Internal Medicine (2010;153:641-649).
As the demand for organ transplants grows—without the supply keeping pace—the development of strategies to increase the pool of available organs is critical. More than 20 European nations have traditionally looked to presumed consent, also known as an opt-out system, as a way to narrow the supply-and-demand gap, wrote the study authors, led by Lucy D. Horvat, MSc, of the Kidney Clinical Research Unit at London Health Sciences Center in London, Ontario.
Ms. Horvat and colleagues conducted this longitudinal study of presumed versus explicit consent in order to inform deliberations on a bill that would make Ontario the first Canadian province to adopt presumed consent, noted senior study author Amit X. Garg, MD, PhD, of the Lawson Health Research Institute in London, Ontario. Like the United States, Canada currently has a system of explicit consent for organ donation.
The study, which was funded by Lawson and the Canadian Institutes of Health Research, reviewed kidney donation rates in 44 nations using data from 1997 to 2007. Of the 44 nations, 22 had presumed consent policies and 22 had explicit consent policies.
The nations with presumed consent policies had higher rates of deceased kidney transplantation than the nations with explicit consent—22.6 transplantations per million population versus 13.9 transplantations per million population—but lower rates of living kidney transplantation—2.4 transplantations per million population versus 5.9 transplantations per million population.
Larger per capita gross domestic product, health care expenditures, and physician numbers were associated with higher rates of deceased and living kidney transplantation.
‘A More Credible Comparison’
This study was better conducted than others examining presumed versus explicit consent, noted Alan Leichtman, MD, Professor in the Department of Internal Medicine at the University of Michigan Health System, who was not involved in the study.
“It's a more credible comparison. The thing that jumps out at me is in those countries that have presumed consent, the total donation rate is 25 per million population, and in those countries that have explicit consent, it's 20 per million population, and so the overall donation rate is 25 percent higher … in those countries that have presumed consent as opposed to explicit consent.
“If I were writing this, that would have been the key message that I would have put forward, and the rest would have been a sort of subtext.
“Now, it doesn't show causality. It might be that in places that are more inclined to have donors, they might be more inclined to be accepting of presumed consent and would have the same rate if they had explicit consent, if there were any way to test that. But I thought that was pretty dramatic.”
In terms of what's driving the results of the study, there are a few possibilities, Dr. Leichtman noted.
“It could be that presumed consent increases deceased donation and decreases living donation, which is what the authors suggested. It also may be that the consequence of presumed donation is to increase donation overall, and if you increase kidney donation, then, presumably, you also increase deceased liver and heart and pancreas donation, so the positive consequences of an increase in deceased donation probably would extend beyond kidney donation.
“Another possibility is that societies adopt the systems that meet their character the best, and maybe this reflects things that we're not measuring in these different societies.”
Rather than just comparing presumed and explicit consent systems across nations, a look at transplantation rates before and after a nation implemented the particular system would have been useful.
“One of the limitations of the study is that they only look at places that already had the systems in place beforehand and didn't change,” Dr. Leichtman said. “Ideally, you'd want to look at societies when they changed to see what happened before and after.”
‘Two Sides to This Issue’
Given the observational nature of the research, the exact relationship between consent type and kidney transplant rates is unknown, agreed William Harmon, MD, Professor of Pediatrics at Harvard Medical School and Director of Pediatric Nephrology at Children's Hospital Boston, who was not involved in the study.
“Two things may exist, but they may not be related,” he said. “And so the issue that comes up is, if we were to adopt the presumed consent model in the United States, would that lead to a higher conversion rate and more organ donors?
“I think the obvious emphasis is to obtain every potential donor that could be had so that we could maximize the transplant rate. It's not clear exactly how many additional donors [a presumed consent system] would add.”
The issue of consent for organ donation is one of culture and politics, Dr. Harmon emphasized.
“In some European countries, the ideas of equality and fraternity and sacrifice of the individual for the whole are very meaningful. The political tradition in the United States is the sanctity of the individual.
“This, like any other value, has strong proponents and has become part of the fabric of the culture, and so in the United States, restriction of individual rights has always met lots of opposition.”
There also is the worry that implementing a system of presumed consent in the United States could have the opposite of its intended effect.
“Another major concern as a transplant community is that if there is presumed consent, it could actually backfire and end up decreasing organ donation in the United States,” Dr. Harmon said.
“The basis of consent is trust that the organs in the system are being retrieved only after the person has been declared dead, only after there is no hope for recovery of the patient, and that all attempts to save the potential donor's life have been exercised before raising the question of whether or not the person would make a good organ donor.”
Presumed consent can be a double-edged sword, he said.
“If you're in a situation where informed consent is accepted by the culture of the community, then there is no question that it probably would increase the organ donation rates. But given the fact that there may be a backlash that led to accusations that the organs were obtained inappropriately, it could lead to a decrease.
“So there are two sides to this issue. The paper demonstrated one upside, which is that it is likely that the adoption of presumed consent, if it were successful, would increase donation rates. It doesn't address the other question, which is, what if there is a backlash?”
Countries that may pursue a strategy of presumed consent should evaluate potential effects first.
“I think countries considering presumed consent should test whether it has a chilling effect on living donation to see whether their total transplant rates go up or down, and they ought to test whether presumed consent increases opportunity for other organ transplants—for heart, lung, liver, and pancreas,” Dr. Leichtman said.