, a provider of recovery audit services to many Fortune 100 companies, is under new ownership.

The privately held, venture-backed company said Thursday that it had been acquired by , a private equity firm in Pittsburgh, Pa.

Financial terms were not disclosed.

Investors in APEX included Noro-Moseley Partners and the Wakefield Group. The company launched in 1988.

APEX developed proprietary software for detection and recovering of payment errors. Its client lists includes 79 members of the Fortune 500, 33 of the Fortune 100 and 10 of the Fortune 25.

Michael Lustig, chief executive officer of APEX, and James Arnold, the company’s president, remain board members.

"Our investment in APEX Analytix, with its highly differentiated product and service offering, reflects our strategy to invest in niche market leaders with sustainable competitive advantages,” said Jack Glover, partner at PNC, in a statement. “Moreover, we believe there is an opportunity to leverage our recent experience in a similar investment to advance APEX Analytix’s value proposition to customers."

Glover and Mike Hand of PNC also will serve on the APEX board as will David Huebner, chairman of Receivable Management Services Corporation. Receivable Management is a former PNC portfolio firm.

“We have a strong partner in PNC Equity Partners,” Lustig said in the announcement. “Their team has demonstrated a deep understanding of all aspects of our services and software, the value delivered to our clients and our business model. We look forward to working with our new board members as we launch into our next phase of growth.”

According to PNC, its average investments range between $10 million and $30 million.