“Shared savings arrangements mean that vendors financially benefit when less care is delivered,” a structure that can create a powerful incentive for companies to deny medically necessary care, said Jennifer Brackeen, senior director of government affairs for the Washington State Hospital Association.

And doctors and policy experts say that’s only one concern.

Rathi said the plan “is not fully fleshed out” and relies on “messy and subjective” measures. The model, he said, ultimately depends on contractors to assess their own results, a choice that makes the results potentially suspect.