CMS has considered two basic options for assigning beneficiaries to an ACO to calculate eligibility for shared savings.  The first option is that beneficiary assignment would occur at the beginning of the performance year on a prospective basis.  The second option is for beneficiary assignment to occur on a retrospective basis based on the actual utilization of primary care services provided by ACO physicians during the performance year.
CMS is proposing the combined approach of retrospective beneficiary assignment for purposes of determining eligibility for shared savings, while also providing beneficiary data (names, date of birth, etc.) and aggregate data for the assigned Medicare beneficiaries during the benchmark period on a prospective basis.  CMS is soliciting comments on this combined approach and any alternate assignment approaches, including the prospective method of assignment.
Few disagree that the calculation of shared savings must take into account beneficiary assignment on a retrospective basis. The Physician Group Practice demonstration shows a 25 percent population variation on assignment from year to year.  So, it is only fair for CMS to award shared savings based upon the actual number of beneficiaries assigned to the ACO.
Advocates for the prospective approach argue that it is fundamental to population management to be able to profile a population, identify individuals at high risk, develop outreach programs and proactively work with patients and their families to establish care plans.  They also argue that this approach would allow ACOs to track prospective targeted expenses in order to gauge their results through the performance year.
It is understandable that ACOs would desire to have beneficiary assignment information on a prospective basis, given the potential operational risks for not meeting the quality and cost savings targets and the expenses involved in setting up and operating ACOs.  The concern over providing prospective data to ACOs is that ACOs might treat this subset of population differently for purposes of sharing savings, while ACOs are supposed to treat all patients equally.  Also, it is unclear how CMS would be able to prevent ACOs from treating patients differently because of the Shared Savings Program.
Regardless of CMS’s decision, ACOs should consider working with physicians to compile  comprehensive data on its patient pool, including Medicare fee-for-service beneficiaries, and perform population management with respect to the entire patient pool to achieve efficiencies and quality standards.   This would allow an ACO to demonstrate that it is not engaging in potentially illegal patient targeting.  Also, by having the discipline for purposes of the Shared Savings Program, ACOs could easily apply such discipline to the entire commercial population and be in a better position to negotiate appropriate incentives with private payers.