DaVita HealthCare Partners Inc. said it has received a subpoena from the Office of Inspector General for documents related to patient diagnosis coding and risk adjustment submission and payments to Medicare Advantage plans and organizations. The subpoena covers documents from January 2008 to present, and includes HealthCare Partners and its subsidiary JSA HealthCare Corporation.

“We believe that the request is part of a broader industry investigation into Medicare Advantage patient diagnosis coding and risk adjustment practices and potential overpayments by the government,” the company said in a filing with the Securities and Exchange Commission.

Some of the information requested relates to “a potentially improper historical HealthCare Partners (“HCP”) coding practice related to a particular condition,” the company said in the form. “The practice in question was discontinued following our November 1, 2012 acquisition of HCP and, as we previously disclosed, we notified the U.S. Center for Medicare & Medicaid Services of the legacy coding practice and potential overpayments.”

DaVita has indemnification rights against the seller, and has established an escrow as security for the indemnification. “We can make no assurances that the indemnification and escrow would cover the full amount of our potential losses related to this matter,” DaVita said.

The company announced in May that it would pay up to $495 million to settle a whistleblower suit in Atlanta.