The chairman of the Senate Finance Committee said Thursday that he is troubled by reports that private contractors for Medicare are not adequately investigating patient complaints about quality, and he asked the federal health program to turn over documents detailing the groups' operations.

Citing recent Washington Post articles about the contractors -- which are known as Quality Improvement Organizations, or QIOs -- and interviews by his staff, Sen. Charles E. Grassley (R-Iowa) wrote to Medicare officials that he is concerned that the groups "have misplaced their priorities." His letter seeks a range of documents covering the QIOs' finances and policies for preventing conflicts of interest, including records of any trips by Medicare officials paid for by the QIOs, as well as any Medicare audits and evaluations of the contractors.

Grassley's letter requests documents from QIOs in 14 states. There are 53 QIOs -- one in each state, plus one each in the District, Puerto Rico and the U.S. Virgin Islands. Medicare pays them $1.3 billion over three years to carry out tasks including investigating complaints about the quality of care received by Medicare patients.

The Post reported last month that the QIOs -- which are dominated by physicians -- investigate few patient complaints and sometimes play a conflicted role. Even when complaints are reviewed, The Post found, patients have less than a 1-in-4 chance of having them confirmed. The number of sanctions QIOs recommend against doctors each year has dwindled from hundreds to a few.

Many of Medicare's decades-old rules governing QIO investigations are shrouded in secrecy and appear to favor physicians. In his letter, Grassley cited the "epic effort" of David Shipp, 75, a Louisville native who was forced to sue Medicare for the results of a QIO investigation of his wife's death. After a four-year legal struggle, the QIO disclosed in 2003 that Shipp's wife had received substandard care but refused to say what steps, if any, it had taken against the doctors.

"The Post's reporting raises a lot of troubling questions," Grassley wrote Medicare officials. "Secrecy and tax dollars don't mix. . . . The taxpayers deserve to know what they are getting for the $300 million a year that they contribute to these groups. And David Shipp deserved to know what happened to his wife without having to sue."

QIO executives and Medicare officials have said they do not know why more patients are not filing complaints. But government investigators have found that the complaint process is poorly advertised, and some researchers contend that the QIOs are reluctant to punish doctors and hospitals with whom they work closely.