But after a two-day conference that ended here on Friday, there was little consensus on how, when or even whether the fragmented young field should unify.

Kidney paired donation, which was first attempted in the United States in 2000, makes transplants possible for renal patients who have a willing donor but who do not match that donor’s blood type or antibodies. Instead of giving a kidney directly to a loved one, the donor essentially swaps an organ with a stranger who also has a willing but incompatible donor.

In another iteration, called a domino chain, a good Samaritan donor gives to a stranger, whose paired donor then gives to another stranger, and so on down the line.

In December, the National Kidney Registry, one of the several nonprofit groups that arrange such swaps, completed a record chain of 30 successful transplants, performed over four months at 17 hospitals.

Nephrologists and transplant experts are hopeful that paired donation might chip away at an ever-expanding waiting list for kidneys from deceased donors, which stood on Friday at 91,681. But of 16,812 kidney transplants performed in 2011, only 429 were through paired exchanges with living donors.

Researchers believe that several thousand transplants might be possible if paired donation were better understood, if more hospitals participated, if practices for evaluating donors and allocating kidneys were standardized and if all pairs of recipients and donors were listed in a single registry.

The current system includes several national and regional registries that are largely unregulated, as well as a pilot program sponsored by the federal government. Some hospitals also make substantial numbers of matches among their own patients.

The conference, attended by about 70 people and held at an airport hotel here near Washington, was organized by several medical societies to seek consensus on ways to increase the number of transplants made possible by paired donation and address potential ethical issues.

One committee, which was charged with examining how kidneys are allocated through paired donation, advised that a single national pool would increase opportunities to make matches among incompatible pairs and to find kidneys for patients who are the hardest to match.

“We should eliminate the barriers to a national registry,” said one of the committee’s leaders, Sommer Gentry, a mathematician at the Naval Academy who studies organ-matching algorithms. “With two pools of 100, you get fewer opportunities than with one pool of 200.”

The committee also concluded that listing pairs of donors and recipients in multiple registries could be counterproductive. Registries with the resources to make the most frequent computer match runs would end up with the best candidates, and other registries might waste time constructing chains with pairs they later discovered were no longer available.

“It causes cherry-picking that undermines optimization,” Dr. Gentry said. “It kind of creates this race to the bottom.”

But Dr. Gentry’s mathematical observations do not take into account the politics of kidney transplantation, where competing registries are sufficiently invested in their own methods and successes to see little advantage in unification.

Garet Hil, the founder of the National Kidney Registry, which has arranged more transplants than any other group, said he did not agree that there needed to be a single system.

“So long as all the transplant centers enter all the pairs into the systems out there, you’re not disadvantaging patients and you are engendering competition,” said Mr. Hil, whose registry is based on Long Island. “The National Kidney Registry has facilitated more transplants than all the other paired exchange programs, and I don’t see the need to try to reinvent the wheel.”

Even the conference’s lead organizer, Dr. Sandy Feng, a transplant surgeon at the University of California, San Francisco, worried that unification might stifle the innovation of successful registries like Mr. Hil’s.

“Maybe we can have different operations with common allocation methods and principles,” she said after the conference. “A national registry may be where we need to be when the field is more mature, but maybe we don’t need to do that right now.”

A number of people at the conference said the federal government should oversee a unified system for living donor exchanges in the way that it currently manages the deceased donor waiting list. The Department of Health and Human Services has long contracted that task to a single nonprofit group, the United Network for Organ Sharing.

Dr. Gentry’s committee recommended that biological traits and medical need should take precedence in determining which transplant candidates are first in line for paired exchange matches. Priority should be given to the patients who are hardest to match, to children and to those who have been waiting for a kidney for long periods, the committee said.

It cautioned against building long chains because they bear a greater risk of falling apart for logistical or medical reasons.

Those attending the conference, including representatives of several major health insurers, agreed that it was important to establish a single reimbursement rate for paired exchanges. The rate must take into account the staff time and technology resources needed to make matches and to arrange the logistics of moving organs across the country. Insurers should compensate living kidney donors for travel and lodging costs, the group said.

The rates currently vary from hospital to hospital, and disputes over how to divide payments between a donor’s hospital and a recipient’s hospital have sometimes posed obstacles.

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Sierra had told her mother, who is a dialysis nurse, that she believed in organ donation, Roxanne Murray said at Friday’s event marking April as Organ Donation Month.

Sierra’s memory and gift of organs was a central message during the event sponsored by the hospital for Life Center Northwest, one of 58 federally designated nonprofit organ procurement organizations.

“I have patients who are waiting for a transplant,” Roxanne Murray said. “This is a great way to honor her.”

“Sierra gave everything she had to anyone who needed it,” said her mother, adding that her daughter had loved singing in the high school choir, but gave it up to become a mentor for youth. Sierra also was active at Temple Baptist Church in Richland and planned to attend college to pursue a career in childhood education.

Friday’s event also had Oscar Sainz, 52, of Kennewick, sharing how a donated heart saved and changed his life three years ago.

“Two granddaughters have been born since the transplant. More than likely
I would not have had to chance to know them without getting a new heart,” said Sainz, who has been a spokesman for organ donation since receiving the heart.

Sainz noted that recipients don’t know who their donors are, but the positive effects to families of both are great.

“To anyone who is hesitant about becoming an organ donor, I say put yourself in my shoes,” he said.

Roxanne Murray said it is still hard to go on without her daughter.

“We’re taking it one day at a time. We always knew she would change the world. We just didn’t know how,” she said.

A memorial for Sierra is planned for Sunday — which would have been Sierra’s 17th birthday — in Richland High’s school’s cafeteria.

The event starts at 2 p.m. and will include a potluck, cake and music. Organizers expect to release 50 purple balloons in Sierra’s honor.

Attendees are encouraged to wear shirts, hoodies or buttons made in Sierra’s memory.

For more information about Life Center Northwest, based in Bellevue, call 888-543-3287 or go to www.lcnw.org.

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President Barack Obama, seeking to
raise $2 million in campaign funds in Vermont and Maine, told
supporters that there may be more at stake in the U.S. election
this year than in his victorious run to the White House in 2008.

“In 2008 I was running against a candidate who believed in
climate change, believed in immigration, believed in the notion
of reducing deficits in a balanced way,” the president said to
about 100 contributors at a luncheon in Burlington, Vermont, the
first of four events yesterday in two states he won by wide
margins in 2008.

“We had some profound disagreements, but the Republican
candidate for president understood that some of these challenges
required compromise,” Obama said, referring to Senator John McCain. Now, he said, Republicans have a “fundamentally
different vision of America.”

Obama has been increasing his fundraising and campaign
appearances as he turns more directly to his re-election
campaign and as the Republican nomination race enters its final
stages. Obama is running with the nation’s unemployment rate
stuck at about 8 percent or higher since he took office and the
threat of higher oil prices stifling the recovery.

Obama raised $45 million for his campaign in February
compared with $11.5 million for Republican front-runner Mitt Romney.

Agenda for Term

In seeking to rev up enthusiasm among his supporters, Obama
cited victories during his first term, including passage of the
health-care law that was the focus of Supreme Court arguments
this week. The remarks on the health-care overhaul marked the
president’s first on the issue this week.

Obama also outlined his future agenda, citing a push for a
minimum tax on individuals who make $1 million or more annually,
an initiative named for billionaire investor Warren Buffett.

The Senate is due to vote on the Buffett rule in two weeks.
It would require a minimum 30 percent tax rate for the highest
U.S. earners. The congressional Joint Committee on Taxation
projects it would raise $47 billion over the next decade.
Republicans, who have enough votes to block the legislation,
have said they oppose it.

Obama linked the tax to his re-election campaign theme that
the U.S. must cut its budget deficit without jeopardizing
education and research programs.

‘Basic Math’

“If you make more than a million dollars a year, I don’t
mean that you have a million dollars; I mean every year they’re
making more than a million dollars, you should not pay a tax
rate that’s lower than your secretary,” he told approximately
1,800 people at Southern Maine Community College. “This is not
class warfare, this is not class envy, this is just basic
math.”

Obama also jabbed at the Republicans running for president
while at the University of Vermont in Burlington. He cited the
debate in the primary battle among Romney, former Senator Rick Santorum and former House Speaker Newt Gingrich, and said
Abraham Lincoln “couldn’t win the nomination.”

Obama was making his first trip to Vermont since taking
office. He won the state by 37 percentage points in the 2008
election. Yesterday marked his third visit to Maine, which he
won by 18 percentage points in 2008.

Vermont residents have made more per-capita contributions
to Obama’s re-election campaign than residents in any other
state, even his home state of Illinois, according to a review by
the Burlington Free Press.

State Visits

The president’s stop in Vermont reduces to seven the number
of U.S. states that Obama has yet to visit since taking office:
North Dakota, South Dakota, Nebraska, Idaho, Utah, Arkansas and
South Carolina. None of these states voted for Obama in his 2008
presidential race against McCain.

Obama has made two trips to Maine since taking office,
including a July 2010 family vacation to Acadia National Park.

Tickets for the first event started at $7,500 per person
and went for as much as $35,800, according to the campaign. In
Portland, Obama spoke to approximately 1,800 people at Southern
Maine Community College. Tickets for those events went for $44
to $100.

At a dinner at the Portland Museum of Art, Obama told about
130 supporters seated around square tables adjacent to an Edgar Degas exhibition that, while the economy is improving, more must
be done to invest in research, education and energy
independence.

“The task before us still looms large and the other side
doesn’t have answers to these questions,” he said at the final
fundraiser of the day. “You don’t see them debating how we
improve our education system; you don’t see them engaging, in
any serious way, about how we’re going to retrain our workers.
There’s not a conversation about how we restore manufacturing in
this country.”

Obama said Republican presidential candidates have “one
message,” which is cutting taxes “so that by every objective
measure our deficit is worse.” Ticket prices started at $5,000
per person.

To contact the reporter on this story:
Kate Andersen Brower in Portland, Maine at kandersen7@bloomberg.net

To contact the editor responsible for this story:
Steven Komarow at
skomarow1@bloomberg.net

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