Since it began three years ago, Medicare's test of accountable care hasn't asked beneficiaries who are not assigned to an accountable care organization whether they want to voluntarily enroll. That will change next year when some Pioneer ACOs will give beneficiaries that option.

The CMS Innovation Center is testing whether seniors will elect to enroll in an ACO, a term that means little or nothing to many patients despite an aggressive push to promote accountable care among hospitals and doctors. The Pioneer ACO demonstration also will evaluate whether patients who agree to enroll are more likely to stay within the ACO's provider network and seek care from ACOs' hospitals and doctors.

Patients' track record in staying within the ACO network has been spotty among Medicare ACOs. Unlike Medicare Advantage managed-care plans, which are allowed to use deductibles and other strong financial incentives to steer patients toward network providers, patients in Medicare ACOs can seek treatment anywhere with no financial penalty. And indeed, they often wander outside the network. That undermines ACO efforts to manage quality and costs and weakens incentives for ACOs to make investments in services or programs that won't deliver immediate returns, experts say.

“We have to be creative right now, in the absence of tools that we have in managed care,” to encourage patients to seek care within the ACO network, said Colin LeClair, executive director of Monarch HealthCare, an ACO that is inviting patients to enroll.

Until this year, patients were enrolled in—“attributed to” in ACO jargon—a Medicare ACO because their doctor was participating. The CMS Innovation Center has included patients within an ACO based on how much care they got historically from ACO doctors. Patients are informed by letter. Currently, patients can opt out of allowing the ACO to share their medical data but they still are included in the ACO's cost and quality baselines and in the ACO's final performance results.

But one-third of patients in ACOs turn over each year because they seek too much care outside an ACO. Nonetheless, Pioneer ACOs are rewarded or penalized based on the cost and quality of healthcare services for patients who are identified and attributed at the start of each year.

That enrollment strategy will continue to be the case next year. But in 2015, additional patients will be able to choose to be enrolled. The Innovation Center said five Pioneer ACOs will solicit patients to enroll. Invitations will go to Medicare patients not included in an ACO in 2015, based on their primary-care doctor this year, but who were previously included.

Signing up for an ACO may make patients more conscious of the quality-of-care benefits of ACO enrollment, and may nudge them to stick with the ACO's network doctors and hospitals, LeClair said. Patients who elect to join also may be more receptive to attempts to manage their care or their chronic disease condition once they are familiar with accountable care, ACO leaders say.

Often seniors feel vulnerable and distrustful about being solicited. But “when we call a high-risk patient or a patient who was just discharged from the hospital, we're not a foreign entity, we're a trusted partner,” LeClair said. “We're here to support them.”

Irvine, Calif.-based Monarch HealthCare mailed invitations to nearly 10,000 Medicare patients, and 2,100 responded, LeClair said. Of those, about 100 declined. Monarch used letters drafted by the Innovation Center, which worked with a behavioral economist to draft four letters to see which version gained the highest response from Medicare patients.

But it's uncertain whether seniors will be willing to change doctors or habits that take them outside an ACO simply because they signed up for an ACO. Beneficiaries in the traditional Medicare program who join an ACO can continue to seek care anywhere and from whomever they would like. “It's not clear that would necessarily change the care patterns,” said Dr. J. Michael McWilliams, an associate professor of health policy at Harvard University who has studied managed care and accountable care.

The invitation to voluntarily join an ACO may confuse seniors, say some ACO executives who decided not to participate in the test of voluntary enrollment. They may mistake the ACO for a Medicare Advantage plan, which restricts their choice of provider.

In Minneapolis, Park Nicollet Pioneer ACO officials feared that this type of invitation would confuse seniors and require significant time and effort from staff to explain the offer. And they thought it ultimately would do little to change patients' provider choices, said Donna Zimmerman, senior vice president, government and community relations for HealthPartners, which includes Park Nicollet.

Her ACO will wait to see whether invitations by Monarch are effective in getting patients to stay within the ACO network. “It's absolutely a fair question and a tactic that can be tried out,” she said.

In Peoria, Ill., where managed care is not as common as in other geographic areas, older Medicare patients have little experience with limited networks and may find the ACO invitation perplexing, said Dr. Ralph Velazquez, senior vice president of care management for OSF HealthCare, which operates a Pioneer ACO. Older seniors may have little appetite for accountable care, he added. OSF is debating whether to invite seniors to participate.

Experts say marketing ACOs to patients could cause risk-selection issues. Recruiting patients creates opportunity for ACOs to pursue those with spending likely to be less than projected and avoid those whose care is likely to exceed projected targets. ACOs earn bonuses when health spending is less than projected, based on patients' historical use.

That potential problem can be minimized, however, to the degree that spending targets account for predictable fluctuations in spending and include adequate risk adjustment for sicker patients, said Michael Chernew, a health policy professor at Harvard University. The better those spending targets adjust for risk, the less worry “about untoward things happening,” he said.

For the coming year, the Innovation Center will use a more sophisticated risk-adjustment formula to adjust spending projections for more complicated, expensive patients, ACO executives said.

Even so, research suggests seniors with cognitive impairment or limitation may be less likely to enroll in an ACO despite potential improvements in their care, McWilliams said. Such patients were less likely to sign up for low-income subsidies for Medicare Part D prescription drug coverage, according to a study McWilliams and others published in 2013 in JAMA Internal Medicine.