CHICAGO_The nation's largest health insurers improved the accuracy of their payments to doctors but are still too inconsistent with claim denials, according to the American Medical Association's latest report card.

The doctor group unveiled its National Health Insurer Report Card last year to rate insurers and spur improvements in claims processing. Their study uses a sampling of claims to measure accuracy, timeliness and denials, among other variables.

The 2009 report card, which was released Tuesday, showed that private insurers more frequently reported the correct rate on claims. It also showed that several insurers made slight improvements in reducing the average time it took to respond to a doctor's claim.

But the 2009 rating also found "wide variation" in how often insurers deny claims and the reasons they use to explain their denials.

The AMA is trying to trim administrative costs by shedding more light on claims processing. The association's leaders have said doctors spend as much as 14 percent of their revenue to ensure accurate insurance payments.

The 2009 report card was devised by sampling about 1.6 million electronic claims submitted between February and March to several large insurers. That list includes Minnetonka, Minn.-based UnitedHealth Group Inc., Hartford, Conn.-based Aetna Inc. and Philadelphia-based Cigna Corp.

To view the report card, visit http://www.ama-assn.org/go/reportcard.