ACOs and the Shared Savings Impact of Imaging

When an MSSP ACO misses its benchmark by 1 percent, the leadership team does not usually point at imaging. They point at inpatient admissions, at SNF length of stay, at post-acute spend, at the handful of catastrophic cases that blew through the actuarial assumptions. Imaging is a line item on a slide, not a lever.

That framing is a decade out of date. For most ACOs we work with, imaging is 3 to 5 percent of total cost of care, it is one of the most variable spend categories on a per-member basis, and it is one of the few line items where an operational change made at the referral moment produces a measurable effect inside a single performance year. Shared savings math is cumulative, and imaging is one of the fastest compounding inputs.

This article is for ACO executives and population health leaders who have been told imaging is "too small" to prioritize. It is not.

The HOPD routing problem

In a typical MSSP ACO attributed population, 60 to 75 percent of outpatient imaging is routed through a hospital outpatient department. The site-of-care variance between HOPD and freestanding imaging on identical CPT codes runs between 2x and 8x. For MRI and CT, the multiples are at the high end of that range.

Two numbers make the point. A screening chest CT in a freestanding center averages $250 to $400. The same study in an HOPD can bill at $1,200 to $1,800. A lumbar MRI without contrast at a freestanding center reimburses at roughly $450 to $700. In an HOPD, that study can reimburse at $1,800 to $2,500.

When you multiply that spread by the volume of imaging orders flowing through a 25,000 life ACO, the annualized variance lands between $2.5 million and $6 million. In a shared savings contract with a 50 percent savings rate, that is $1.25 million to $3 million of retained margin that can be captured or lost based entirely on where the patient walks in.

Why routing is the leverage point, not utilization

The instinct in value-based care is to reduce utilization. Fewer MRIs, fewer CTs, tighter imaging appropriateness protocols. Those programs have value, but they are slow, clinically contested, and politically hard inside a mixed specialist network.

Site of care routing is different. It does not require reducing a single study. It does not ask providers to change their ordering behavior. It does not require an appropriateness committee. It asks one question at the moment the order is placed: can this study be done at a lower cost site of care that is in network, in quality, and convenient for this specific patient.

When that question is answered operationally, not aspirationally, the savings show up in the claims data within 60 to 90 days. That is the fastest feedback loop any ACO lever provides.

What an ACO actually needs to capture this

Three operational pieces have to line up for site of care routing to work at scale:

1. A decision engine at the point of referral. The referring provider or their coordinator needs to see, in their workflow, which freestanding option fits this patient's plan, geography, urgency, and clinical needs. Not a phone call to a shared services team. Not a fax to a coordinator. A real-time routing decision.
2. Patient-level engagement. Freestanding facilities are less familiar to patients than the hospital down the road. Without active scheduling support and reminders, 25 to 40 percent of patients who are routed to freestanding drop off and self-schedule at the HOPD anyway. The routing decision is only as good as the completion rate behind it.
3. Closed-loop reporting. The ACO has to be able to see, at a monthly cadence, the percentage of attributed imaging done at each site of care, the per-member variance against the prior year, and the projected annualized impact. Without that reporting, the program becomes invisible inside the broader MSSP narrative.

The timeline to benchmark impact

For MSSP ACOs on a January 1 to December 31 performance year, the operational window is tighter than most leaders realize. A site of care routing program launched in Q2 captures roughly 6 to 7 months of savings inside the current performance year, which is typically enough to move the needle on the final reconciliation.

A program that launches in Q3 or Q4 captures very little within the current year but is well positioned for the following performance year. A program that waits for the next strategic planning cycle captures nothing.

In our data, ACOs that operationalized site of care routing by mid-Q2 saw an average per-member imaging spend reduction of 8 to 14 percent by year-end. In mature contracts, that single lever accounted for 15 to 25 percent of the total shared savings captured.

Imaging is the lever that is sitting there

VBC performance is rarely decided by one dramatic intervention. It is decided by five or six smaller interventions that each contribute a point or two of margin and compound into a number that clears the benchmark.

Imaging routing is one of those. It is fast to operationalize, it does not require clinical buy-in to change ordering patterns, it produces results inside a single performance year, and it compounds every year the contract renews.

If your ACO is looking for its next 1 to 2 points, imaging is almost certainly where it lives.

Medmo has partnered with MSSP ACOs to route imaging at the referral moment and deliver measurable per-member savings inside a single performance year. If you want to see what the opportunity looks like in your attributed population, request a site of care analysis.