A Targeted Analysis of Medicare Patient Attribution Reveals Opportunities for Cost Reduction

From the 2019 HVPAA National Conference

Dr. Hisham Yousif (Johns Hopkins Hospital), Dr. Andrew Hughes (Johns Hopkins Hospital), Ms. Sarah Himmelrich (Johns Hopkins Hospital), Dr. Sarah Johnson Conway (Johns Hopkins Hospital)


The Johns Hopkins Medicine Alliance for Patients (JMAP) is a Track 1 Medicare Shared Savings Program (MSSP) accountable care organization (ACO) responsible for improving the quality of care while reducing unnecessary cost for Medicare beneficiaries across Johns Hopkins Medicine and our affiliated practices.


Beneficiary attribution for MSSP ACOs is a retrospective process occurring at the end of a performance year. This attribution drives calculations of cost and quality performance for the ACO against an individualized benchmark. The assignment and categorization of these beneficiaries is central in determining ACO performance on core measures.  Within the JMAP ACO, we identified select high cost beneficiary populations, including non-continuous and newly enrolled patient populations.  Through detailed chart and utilization reviews, we sought to identify unique themes and modifiable factors that potentially drive utilization.


A targeted analysis of ACO beneficiary attribution was completed to define core patient categories.  Beneficiaries were stratified by enrollment status – continuous, non-continuous and new entrant – as well as by provider attribution – primary care (PCP) or specialty attributed.  We identified patient groups with the highest observed over expected cost based on their HCC score.  From these groups, beneficiaries were randomly selected and evaluated to see if they met inclusion criteria defined as costs >200% expected in the performance year and alive at the time of analysis.  60 detailed beneficiary chart and claims reviews were completed – 40 attributed to PCPs, and 20 attributed to specialists. These were stratified based on four target categories – New enrollee PCP attributed (20), new enrollee specialty attributed (10), non-continuous PCP attributed (20) and non-continuous specialty attributed (10) – to assess cost and attribution trends within a performance calendar year.  Results were subsequently thematically categorized for review.


Within beneficiary subgroups attributed to PCPs, we found 35% of beneficiaries were potentially misattributed (30% of non-continuous and 40% of new enrollees). The largest contributor to misattribution was subspecialty Nurse Practitioner (NP) attribution as PCPs, accounting for 33% in non-continuous and 63% in new enrollee groups.

Within beneficiary subgroups attributed to specialists, we estimated that 50% of non-continuous beneficiaries were potentially misattributed (5/10). We were unable to deduce estimates for new enrollee beneficiaries.

In terms of cost drivers, 45% of PCP-attributed patients were high cost due to episodes of surgical care, while 35% of PCP-attributed patients were high cost due to cancer related treatments.


While in search of modifiable risk factors for patients attributable to our ACO that could be managed through improved care coordination or outreach strategies, we found many of the highest cost beneficiaries to be high cost due to a single complicated episode of care often related to a surgical procedure or to high cost treatments related to cancer.  The attribution of these beneficiaries to our ACO was often driven by provider assignment issues, such as NP attribution occurring as primary care.  These issues, we suspect, would affect many ACOs, although they may be more prominent in a large academic medical institution with subspecialty care delivered by advanced practice providers in conjunction with physicians.

Implications for Patient Care

As ACOs seek to improve care and “bend the cost curve”, deeper understanding of their patient attribution is needed to determine how best to target resources and to better understand the components of their assigned beneficiary care that are truly modifiable.

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