Impactability models for high-need high-cost patients: Evaluating their effectiveness in reducing Medicare ACO payments and hospital events (Preprint)

Abstract

Impactability modeling promises to help solve the nationwide crisis in caring for high-need high-cost patients by matching specific case management programs with patients using a “benefit” or “impactability” score, but there are limitations in tailoring each model to a specific program and population.

We evaluated the impact on Medicare ACO savings from developing a benefit score for patients enrolled in an historic case management program, then prospectively implementing the score and evaluating the results in a new case management program.

We conducted a longitudinal cohort study of 76,140 patients in a Medicare ACO with multiple before-and-after measures of the outcome using linked electronic health records and Medicare claims data from 2012 to 2019. There were 489 patients in the historic case management program and 1,550 matched comparison patients; 830 patients in the new program with 2,368 matched comparisons. The historic program targeted high-risk patients and assigned a centrally-located registered nurse and social worker to each patient. The new program targets high- and moderate-risk patients and assigns a nurse physically located in a primary care clinic. Our primary outcomes were any unplanned hospital events (admissions, observation stays, and ED visits), count of event-days, and Medicare payments.

In the historic program, as expected, high-benefit patients enrolled in case management had fewer events, fewer event-days, and an average $1.15 million reduction in Medicare payments per 100 patients over the subsequent year when compared to matched comparisons. For the new program, high-benefit high-risk patients enrolled in case management had fewer events, while high-benefit moderate-risk patients enrolled in case management did not differ from matched comparisons.

Although there was evidence that a benefit score could be extended to a new case management program for similar (i.e., high-risk) patients, there was no evidence that it could be extended to a moderate-risk population. Extending a score to a new program and population should include evaluation of program outcomes within key subgroups. With the increased attention to value-based care, policy makers and measure developers should consider ways to incorporate impactability modeling into program design and evaluation.

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