MSSP is CMS’s largest, most established accountable care program, with 480+ ACOs and gross savings totaling $13.3B+ since 2012. The program was created in 2010 with the ACA and is administered by CMS, rather than CMMI. In theory, all of CMMI’s ACO models are informing what the government should do at the CMS level. So, ACO models administered by CMMI (i.e., ACO REACH, CKCC) are being tested to inform MSSP. For these reasons, CMS has dubbed MSSP the “chassis for innovation” and will likely add onto its framework.
MSSP’s early tracks are designed for less-experienced ACOs, allowing them to gradually assume more financial risk as they gain experience. These ACOs progress along a structured “glide path,” moving from the lower-risk Basic A level to the highest-risk Enhanced (EN) track.
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Alignment Methodology
Like REACH, MSSP’s alignment methodology offers both voluntary alignment and claims-based alignment, whereas CKCC does not offer these options (for more information, see page 11 here). The beneficiary (bene) must meet the following criteria for them to be eligible for assignment:
- Has at least 1 month of Part A and Part B enrollment
- Does not have any months of Part A only or Part B only enrollment
- Does not have any months of Medicare group (private) health plan enrollment
- Is not assigned to any other Medicare shared savings initiative
- Lives in the United States or U.S. territories and possessions
Alignment Minimums: ACOs must have at least 5,000 assigned Medicare fee-for-service beneficiaries to participate. This number is higher than CKCC and certain tracks in ACO REACH.
Alignment Visits: Across voluntary and claims-based alignment, the beneficiary must receive Primary Care Qualified Evaluation and Management (PQEM) services annually from the designated ACO provider (i.e., has an office visit each year).
- PQEM services ****are primary care services furnished by a primary care specialist / selected non-primary care specialist, or any service furnished by a Federally Qualified Health Center (FQHC).
- A selected non-primary care specialist is a physician or Non-Physician Practitioner (NPP) whose primary specialty is not in primary care but who may still provide primary care services. CMS will specify a list of CMS specialty codes for selected non-primary care specialists prior to the start of the performance year (PY). Nephrology, preventative medicine, and hospice / palliative care are included in this list (see page 44 for full list).
- Primary Care Services: As of 2024, brief offices visits, SNF visits, AWVs, and phone calls with established patients are considered primary care services (see page 123 for the full list).
Voluntary alignment: Benes designate a provider who they believe to be responsible for coordinating their overall care, taking precedent over claims-based assignment.
- In addition to the bene being alignment eligible, an ACO must have the most recent voluntary alignment attestation, and the bene must receive PQEM services annually from the designated ACO provider (i.e., has an office visit each year).
- In REACH, this attestation an be done with paper and online, whereas in MSSP, this can only be done online, via Medicare.gov.
Claims-based assignment: CMS determines whether allowed charges for a bene’s primary care services in an ACO are greater than the allowed charges for the bene’s primary care services for any other provider.
- While MSSP allows services provided by Advanced Practice Providers (APPs) - including Nurse Practitioners, Physician Assistants, and Clinical Nurse Specialists - to count toward plurality, it requires that a PCP see the beneficiary within the prior 12 months for assignment purposes. In contrast, ACO REACH does not impose this requirement, so APPs can align benes without a prior visit from the PCP.
Prospective attribution: Patients are assigned at the start of the contract PY based on claims in the prior calendar year, which allows ACOs to know their defined population and provide care management during the PY. ACOs can decide between these two prospective models at the beginning of the year.
- Preliminary prospective assignment with retrospective reconciliation: Assigns beneficiaries in a preliminary manner at the beginning of a PY, quarterly, and at end of PY (for both claims-based and voluntary).
- Prospective assignment prior to the start of each agreement period: Benes are prospectively assigned via claims and voluntarily at the beginning of the year. Once a beneficiary is prospectively assigned to an ACO for a benchmark or performance year, the beneficiary is not eligible for assignment to a different ACO.