By Lena H. Sun

They are the most powerful group of doctors no one has ever heard of — 16 physicians who decide which checkups and tests Americans need to stay healthy. But increasingly, their work is more controversial than obscure.

The doctors sit on the national task force that told most women to forget about yearly mammograms until they turn 50, raising an uproar that had barely quieted by the time the group then decided most men shouldn’t be screened for prostate cancer.

These recommendations did more than just rattle ordinary Americans, who thought earlier and regular testing would help to protect their health. They set off far larger reverberations, provoking advocacy groups, medical organizations and lawmakers and triggering questions about the very meaning of preventive medicine and about conflicts between politics and science.

Supporters and detractors agree that the tensions speak to the larger issues looming over mammograms, colonoscopies and screenings for problems such as autism, diabetes and hepatitis C. Evidence and emotion often clash.

“A woman with breast cancer, with little children — there’s nothing that attracts our human emotion more than that kind of suffering,” said Lawrence Gostin, a global health law expert at Georgetown University. “So it makes it really hard politically and otherwise to say, ‘Well, what does the science tell us?’ . . . What you have is a continual struggle between politics and science.”

The issues are complicated by a basic misperception about preventive medicine — by lawmakers as well as the public. Most people think it’s better to be safe than sorry. Better to get tested, even if there’s little or no chance of finding something that could cause problems over an individual’s lifetime.

But prevention can have a downside. False positives can trigger unnecessary anxiety or procedures that carry some risks. With the most common prostate-cancer screening tests, the task force found, about 80 percent of positive results were actually false-positive ones that led some men to undergo biopsies, risking infection, bleeding and urinary difficulties.

“It’s hard to get around the idea that you might find something out and that might not matter to you,” said task force member Alex Krist, a primary-care physician in Fairfax, Va. “But even in cancer, it might never affect you in your life.”

The task force’s authority makes it a prominent target. Unlike other public-health-policy bodies, virtually all of which consider studies and clinical trials alongside cost factors and input from patients, advocates and others, its members look only at empirical data. And then, thanks to the ACA, its recommendations set the baseline for which preventive services get covered.

That authority is “a double-edged sword,” said Ned Calonge, who led the task force in 2010. “On one side, you’re a scientist and you want to make sure your work has impact. But on the other side, this direct link to an economic outcome puts a pressure on your decision-making that I feel is not positive.”

These days, it often means intense attention. Chairman Albert Siu says he and his colleagues definitely feel the scrutiny; ignoring it is the challenge. “Our job is solely to interpret the science,” he noted recently.

Siu, who heads the geriatrics and palliative medicine department at the Mount Sinai School of Medicine in New York, has been on the panel for a decade. He says he gets asked far more today than in his early years to meet with groups with a vested interest in upcoming determinations — pharmaceutical companies, makers of medical devices, professional medical societies, even investment firms

Past members and staffers also get solicited. Kenneth Lin, a former science officer for the task force, was approached last year by a consulting firm interested in knowing whether the panel might support an alternative to colonoscopies in its draft guidelines on colon cancer screening. A strong recommendation — which ultimately did not occur — would have ensured huge sales for the firm’s client.

The task force, which currently includes 10 men and six women, dates to the Reagan administration. When it was created in 1984, with members appointed by the Agency for Healthcare Research and Quality, part of the Department of Health and Human Services, the concept of insurance coverage for preventive services was novel. The few recommendations about checkups that existed were based on specialists’ expert opinions.

This body was designed to have evidence reviewed by primary-care doctors, as opposed to cardiologists or oncologists who might have some “skin in the game,” said Steve Woolf, a professor of family medicine at Virginia Commonwealth University and a former panel staffer and member.

Controversy erupted early on, when the White House intervened before the task force’s first report could be printed in 1989. The reason? Some Reagan administration officials did not like a reference to abortion in one chapter and references to screening for illegal drugs in another, Woolf recalled. The chairman had to fly from Boston to meet with White House officials, the contentious wording was changed, and the report had to be printed privately rather than by the Government Printing Office.

That episode was a minor dust-up compared with what happened in 2009, when the task force concluded that women would get the most benefit from regular mammograms starting at age 50 — not 40, as the American Cancer Society and other organizations had long advised. The rationale was that the older-age threshold would prevent more patients from being subjected to unnecessary biopsies, radiation and stress.

The shift sparked a firestorm. Then-HHS Secretary Kathleen Sebelius was forced to issue a statement reassuring women that they could do what they had always done: consult with their doctors and make individual decisions. The new guidelines did not set federal policy, she stressed — and Congress made sure of that by voting to waive the panel’s guideline.

The following year, a recommendation against routine prostate cancer screening for men again put the task force on the line. Depending on who’s talking, the group’s scheduled vote on the day of the 2010 midterm election was delayed either because the chairman feared that another uproar could jeopardize the panel’s existence or because the Obama administration feared it might tilt the election.

Despite all the changes in health care during the past three decades, the task force continues to rely on essentially the same process for basing its recommendations. Members, who receive no compensation during their four-year terms, hold weekly teleconference calls to go over data and meet in person three times a year. They often take months to make a recommendation, which is designated “A” or “B” if the evidence shows that benefits outweigh harms, “C” if there’s modest net benefit or “D” when harms outweigh benefits or provide no benefit. Insufficient evidence gets an “I.”

Some doctors say the more recent disputes over the panel’s guidance have made them less likely to follow its advice. It’s hard to know whether this is really happening. Specialists such as gynecologists may choose to follow guidelines for earlier-age mammography, for example, because the most aggressive approach is “generally more protective” if a doctor is sued for malpractice, said Barbara Levy.

In January, the task force reaffirmed its breast cancer screening recommendation: Regular mammograms should start at age 50. But Congress had done an end run weeks before, directing insurers to rely on a 13-year-old guideline calling for screening to begin at 40.

The lawmakers’ move, which means that most women in their 40s will be able to keep getting annual mammograms at no cost, brought the debate full circle.

Groups including the National Breast Cancer Coalition decry what they consider political interference. “At some point we will have to decide that we are not going to pay for interventions that lack a high level of medical evidence,” coalition President Fran Visco said.

Such groups as the American Cancer Society say the best way to shelter the task force from even subliminal pressure is to keep it focused on what the evidence shows. Figuring out how that translates into what insurance should pay for ought to be the job of a separate entity, one that ACS notes could weigh broader public-health and social impacts.

For instance, if colonoscopies are strongly recommended as a preventive service — therefore costing consumers nothing extra — does the coverage also include the anesthesiologist involved in the procedure? What about the office visit that takes place beforehand? And what happens if the doctor finds a polyp and a pathologist determines it is benign — is it still covered? (Yes to all.)

Task force members “were pigeonholed into this role,” said Caroline Powers, a director of federal affairs for the cancer society’s advocacy arm. “It’s an inappropriate role.”