Cigna created a home visit program for Medicare patients that artificially inflated government payments by intentionally incorrectly diagnosing tens of thousands of patients with serious illnesses, a lawsuit against the insurance giant alleges.

The Department of Justice (DOJ) on Monday announced its intervention in a lawsuit originally filed in 2017 by whistleblower Robert Cutler, an attorney who previously worked for a Cigna vendor, under the qui tam provisions of the False Claims Act. The DOJ seeks damages and penalties for the alleged filing of false claims resulting from visits carried out by vendors under Cigna’s “360 home visit program.”

The government also charged Cigna with using false records and making false statements, unjust enrichment, and payment by mistake, according to its intervenor complaint.

Cigna receives billions of dollars of payments annually from the Centers for Medicare and Medicaid Services (CMS). It knew the diagnosis codes it used in the claims it filed under its 360 home visit program “were likely false and invalid,” the DOJ alleged.

The company’s misconduct not only led to false claims and overpayments to Cigna—it also “adversely affected the integrity and accuracy” of the diagnosis coding system at the CMS, the DOJ said.

Cigna filed claims from 2013-18 seeking high payments for services for supposedly seriously ill patients who had been diagnosed by nurse practitioners, hired by third-party vendors, who visited the homes of Medicare patients, the DOJ said. The diagnoses were made without providing evidence through tests, images, or medical records, the agency said, of the need for the services.

The nurses allegedly did not order or conduct tests, treat the patients, or refer them for care because Cigna prohibited them from doing so. Nurses working under Cigna’s 360 program made more than 297,000 home visits from 2013-18, according to the complaint.

The nurses typically spent no more than 30 minutes with a patient during home visits, which “were, in essence, brief patient screenings,” the DOJ said.

Cigna’s compliance staff expressed concern about the 360 program and the “risk of reporting ‘diagnoses that cannot be diagnosed in a home visit’” as far back as 2011, but the company didn’t address the concerns, the DOJ alleged.

Cigna’s chief medical officer acknowledged during a 2013 meeting the home visit program was designed to achieve “‘revenue generation,’” according to the complaint. The company “encouraged” vendors to prioritize diagnosing any of 12 conditions and tracked their performance monthly, the DOJ said.

A senior Cigna employee allegedly referred to conditions including diabetes with complications, major depression, and vascular disease as “‘golden nuggets.’”

Cigna misled the CMS when it raised concerns about the home visits in 2013 by omitting important details about the program, the DOJ said.

“Cigna obtained tens of millions of dollars in Medicare funding by submitting to the government false and invalid diagnoses for its Medicare Advantage plan members,” U.S. Attorney Damian Williams of the Southern District of New York said in a press release. “Cigna knew that, under the Medicare Advantage reimbursement system, it would be paid more if its plan members appeared to be sicker.”

“We reject these allegations and will vigorously defend our Medicare Advantage business against them,” a Cigna spokesperson said in an emailed statement. “We are proud of the high-quality, affordable Medicare Advantage benefits we are privileged to provide to beneficiaries nationwide in compliance with government rules.”