Three top Republican members of Congress are asking whether some states have been getting extra cash out of the Affordable Care Act Medicaid expansion program by assigning expansion enrollees extra high health risk scores.

Researchers have reported early signs that the Medicaid expansion program may be increasing poor Americans’ access to health care and improving their health. Some health policy watchers close to Republican lawmakers say some form of Medicaid expansion may have a shot at surviving ACA repeal or overhaul efforts.

Related: What if the ACA exchanges die and Medicaid expansion lives?

But Rep. Tim Murphy, R-Pa., and Rep. Joseph Pitts, R-Pa., have joined with Sen. Orrin Hatch, R-Utah. They suggest in a letter sent to Andrew Slavitt, the acting administrator of the Centers for Medicare & Medicaid Services, that there also are signs some states could be gaming the Medicaid expansion program system to maximize the amount of cash they get from the federal government.

The ACA provides cash that states can use to make Medicaid available to all adults with incomes up to 133 percent of the federal poverty level. The federal government has been paying the full cost of Medicaid expansion up till now. The ACA calls for states to pay 5 percent of the bill starting in 2017.

States and the federal government are spending a total of $545 billion, or about $6,600 per person, to cover 82 million people this year, the lawmakers write in their letter.

Murphy, Pitts and Hatch note that a state can get more reimbursement cash from the federal government if an enrollee has a higher health risk score.

The lack of a need for a state to help pay any of an expansion enrollee’s costs, or “capitation rate,” up till now may have given states an extra incentive to assign high risk scores, the lawmakers suggest.

CMS actuaries originally predicted expansion coverage would cost Medicaid programs $4,281 per expansion enrollee in 2015, but the actual cost was $6,366 per enrollee, the lawmakers write, citing CMS figures.

The lawmakers write in the letter that predicting the cost of a new health program can be difficult, but they ask Slavitt for information about how CMS is analyzing the state reimbursement rates.

Hatch’s participation is noteworthy because he helped create the Children’s Health Insurance Program, the biggest new federal health coverage program organized before the ACA came along in 2010.

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