By SARAH KLIFF

This afternoon, in a hotel ballroom in Northern Florida, two dozen health policy wonks are quietly embarking on a momentous task

: Determining what medical treatments are the most effective.

The health reform law established the Patient-Centered Outcomes Research Institute (PCORI) as an independent advisory board with a $3 billion budget to support comparative effectiveness research. These are studies that probe which medical interventions are best at treating particular conditions and illnesses. PCORI kicks off a meeting this afternoon in Jacksonville, Fla., that you can watch on webcast here and which continues through Thursday. The group has unveiled the blueprint of its research plan, a national priorities and research agenda that could very well decide the success of health-care reform.

For those who haven’t followed the PCORI play-by-pay, here’s a quick backgrounder: The Government Accountability Office appointed an inaugural board of governors in September 2010. The group is led by Executive Director Joe Selby, a former director of research for health insurer Kaiser Permanente. Over the past year, PCORI has held meetings across the country to gather input on how the group should focus its research.

The health reform law prescribes some of PCORI’s activities: The law created the board to focus on comparative effectiveness research, which explores what medical treatments work compared to all those that might be available for a given condition. At its best, such research looks to identify what treatments will lead to the best health outcomes, ideally giving patients and doctors better information on the care they receive. There is also hope that PCORI’s work can reduce the cost of health care with a better understanding of which interventions do not result in improvement, which would in turn allow both the government and private insurers to focus their resources on high-value treatments.

But comparative effectiveness research can be tricky. Study methods can be faulty and results contradictory; a particular medical intervention may work for one subset of patients but not for a larger population. These studies can also be controversial, and they sometimes meet with accusations of rationing. Government recommendations on PSA tests for prostate cancer and to change the frequency of breast cancer screenings met with public uproar.

PCORI’s success, however, is integral to the rest of the health reform law’s work. Its research on what works in medicine will inform decisions made by the Independent Payment Advisory Board. That’s the board that will make binding recommendations on what Medicare ought to cover as a means to reduce costs. It has weathered attacks from both Democrats and Republicans that it could limit the treatments seniors receive. But its long-term survival may rest on the credibility of PCORI’s research.

In laying out its national research agenda this afternoon, PCORI made an interesting choice (or, interesting as choices of bureaucratic boards go). It will focus on researching the most effective medical treatments and preventive medicine. It will look at how health systems can best organize to deliver care, and how to reduce health care disparities in the United States. But it will also give a lot of weight to how to communicate about those treatments, how to convey to patients what works and what doesn’t.

“You see an emphasis on research into communication,” says Yale University’s Harlan Krumholz, a PCORI board member. “We’re always dealing with issues of uncertainty. There’s no answer. There’s no verdict here. There are possibilities that are available and they have trade-offs. What’s here is an investment in not only generating knowledge but also investing in research to help practitioners and patients understand that knowledge.”

Figuring out what works in medicine is a big battle — but, as Krumholz points out, might only be half of PCORI’s task. The other half, of communicating about what works in medicine, will be just as difficult, and just as important, a task.