Accountable care organization leaders detail wins, and unfinished business, in Medicare reform

Accountable care organizations (ACOs) have become an effective tool for Medicare to generate savings and catch health care fraud, said two advocates who described their firsthand experience with the model.

Aisha Pittman, M.P.H., senior vice president of government affairs at the National Association of Accountable Care Organizations (NAACOS), and Katie Boyer, M.P.P.A., director of policy and government affairs at Agilon Health, spoke during a conversation moderated by Mara McDermott, J.D., chief executive officer of Accountable for Health, during the PrimaryCare26: See the Possibilities conference held by Primary Care for America earlier this month.

Their conversation covered recent wins for the accountable care model, the role ACOs have played in surfacing Medicare fraud, and policy fixes that ACO advocates want to see. They also discussed next generation of Medicare accountable care models and how artificial intelligence is reshaping both the back office and patient care.

A strong track record

Agilon, which partners with independent primary care practices in 12 states and more than 30 communities, had eight ACOs in the ACO REACH program covering more than 120,000 Medicare beneficiaries in 2024, Boyer said. Four of those ACOs posted perfect quality scores, with the network averaging 96, and the group helped the Medicare Trust Fund save more than $54 million that year, she said.

The Medicare Shared Savings Program (MSSP) is approaching 15 years old, and roughly 51% of traditional Medicare beneficiaries are now in some kind of accountable care relationship, Pittman said. She put total net savings to the government at roughly $38 billion over the life of the program.

Catching fraud, but paying for it

Medicare spending on skin substitutes grew from about $250 million in 2019 to more than $19 billion in 2025, and a wave of catheter fraud emerged the year before that, Pittman said. Those are examples of the kind of pattern ACOs are positioned to catch early. ACOs are required to report suspected fraud, waste and abuse to the government, she said, but rarely learn what happens to those reports afterward, calling it a "black box" that leaves practices without a clear answer for beneficiaries.

Medicare sometimes withholds payment on suspected fraudulent claims by placing them in escrow during an investigation, a process that can reduce an ACO's shared savings or even push it into owing shared losses, Pittman said. That happens even when the ACO itself flagged the activity.

"We just believe we shouldn't be held accountable for fraud that we're discovering, communicating with beneficiaries about, and reporting to the government, and so we want to see stronger policies," Pittman said.

Cross-organization collaboration, convened through groups like NAACOS and Accountable for Health, has been critical to spotting these patterns, Boyer said, since one ACO often first identifies an issue that others can then investigate in their own data.

“Health plans have had this sort of system of communication around bad actors and fraud and abuse and patterns in the data that ACOs until this year hadn't been invited to participate with, and now they are,” McDermott said. “So I do feel like we are making progress. We still have a long way to go, but it's really a testament.”

Fixing long-standing problems

Despite that track record, structural problems in Medicare's accountable care programs are limiting further investment in primary care, Pittman said. Long-tenured ACOs, for instance, see their benchmarks recalculated downward the longer they participate, which shrinks the shared savings available to reinvest in patient care. She grouped the fixes she'd like to see into three categories:

• Financial sustainability: addressing the way long-tenured ACOs' benchmarks are recalculated downward over time.
• Burden reduction: lowering the volume of quality reporting requirements placed on participating practices.
• Innovation: bringing approaches already tested in CMS's Innovation Center, such as primary care capitation and hybrid payment models, into the permanent MSSP, which hasn't changed much since 2019.

Congress also has a role to play, Pittman said, because ontinued investment and strong incentives to join and stay in accountable care models remain important. She cited the Medicare Access and CHIP Reauthorization Act of 2015, the law that created incentives for practices adopting advanced payment models, as an example of legislation that successfully drove greater investment in primary care. Advocates are watching for a similar push from physician lawmakers, she said.

The next model: LEAD

The CMS Innovation Center's new Long-term Enhanced ACO Design (LEAD) model, the latest in a series of Medicare accountable care models dating back roughly 15 years, has been a "labor of love" to help develop, Boyer said. Its 10-year duration and lack of benchmark rebasing are major improvements, she said, along with an approach that credits ACOs for savings they've already achieved in prior models. That's been difficult for long-tenured, high-performing ACOs to get credit for in the past, Boyer said.

LEAD also aims to integrate specialty care into risk arrangements alongside primary care, a longstanding challenge for primary care-led ACOs trying to manage a patient's full course of care without steering them toward unnecessary higher-acuity treatment, Boyer said. Agilon is still waiting on additional financial details before finalizing its participation, she said, but expects to take part in some form.

LEAD also creates a dedicated pathway for organizations serving higher-need, higher-complexity patients, building on an approach ACO REACH tested separately, Pittman said. Many large ACOs are applying to both LEAD and the Shared Savings Program while they wait for final financial methodology before deciding where to focus, since the choice often comes down to how much financial risk an organization is prepared to take on, she said.

AI shifts toward patients

AI use among Agilon's partner practices has moved beyond administrative tools, such as ambient scribes that reduce time spent on documentation, toward more clinical and patient-facing applications, Boyer said. Some practices now layer diagnostic support tools on top of those scribe notes, prompting physicians to consider additional diagnoses based on symptoms and medications already documented, without making the decision for them, she said. One practice, Boyer said, built an AI care coordinator that checks in with patients daily by text message, helping decide whether a patient needs an urgent visit or can wait for a scheduled appointment.

Many of NAACOS members' assumptions have been challenged, Pittman said, noting that patients have shown more willingness to use virtual care tools than expected. Because ACOs are largely funding AI tools out of their shared savings today, which reduces what's distributed back to participating practices, members are watching CMS's new Advancing Chronic Care with Effective, Scalable Solutions (ACCESS) model, which tests direct payment for these tools, closely, she said. Vetting which AI vendors can be trusted to deliver real value, and ensuring that data from AI tools patients use gets back to their primary care physician in a timely way, are the two biggest concerns among members, Pittman said, particularly when the ACO has no financial relationship with the vendor.

Looking five years ahead

Looking out five years, Boyer said policymakers should eventually treat accountable care models consistently across both traditional Medicare and Medicare Advantage so that patients receive comparable access to coordinated care regardless of which program they're in. That will also require more education for lawmakers and regulators, she said, about how policy changes to these models ultimately affect the primary care practices and other providers carrying the financial risk underneath them.

A "pie in the sky" goal would be 100% of traditional Medicare beneficiaries in an accountable care relationship, up from about 51% today, Pittman said. Another goal: roughly doubling the share of Medicare Advantage patients in physician-led, risk-based arrangements, which Pittman put at around 30% in the most recent landscape survey. She also said she expects more innovation in how these models are structured in the years ahead, including ideas tied to AI that haven't been developed yet.