The American Hospital Association is urging the Department of Justice to thoroughly investigate UnitedHealth Group’s proposed acquisition of radiology vendor Change Healthcare, officials with the influential lobbying group said Wednesday.

UH first announced the blockbuster, $13 billion deal in January, planning to fold the imaging tech company into its Optum business unit. But the hospital group is concerned the deal will reduce competition for the sale of health IT services, negatively impacting consumers and physicians, AHA General Counsel Melinda Reid Hatton argued.

“Indeed, the parties are well aware that the transaction presents substantial antitrust concerns because the transaction agreement provides that the parties will divest assets that generate hundreds of millions of dollars in revenue in order to obtain DOJ approval,” she wrote to Acting Assistant Attorney General Richard Powers on March 17. “The proposed acquisition also would produce a massive consolidation of competitively sensitive healthcare data and shift such data from Change Healthcare, a neutral third-party, to Optum, a subsidiary of [UnitedHealth Group].”

She further argued that because Optum’s parent owns the nation’s largest health insurance plan, the combo would likely impact and distort decisions around patient care, claims processes and denials.

Those involved said in January that they hope to close the deal in 2021’s second half, subject to approval by both Change shareholders and the feds, among other conditions.

“Optum and Change Healthcare share a vision for better health outcomes and experiences for everyone, at lower cost,” a spokeswoman for the former said in a statement in response to the AHA’s letter. “With distinct and complementary capabilities, this combination will help healthcare providers and payers better serve patients by more effectively connecting and simplifying key clinical, administrative and payment processes to the benefit of the health system and the people we serve.”