The two major buying groups say they are accountable only to those hospitals that own them.
No one knows how much money the buying groups save hospitals.
The buying group plans on making certain improvements to the building, with the details to be announced in early 2007.
That arrangement has led to questions about whose interests the buying groups really serve.
"This lack of consistent price savings is contrary to what would be expected for large" buying groups, the study found.
That subcommittee held a hearing in April on the buying groups.
Since management is part of the buying group, it already feels like an inside job.
He added that officials of the buying groups had moved to bar member hospitals from reviewing his company's equipment.
He cited "the extensive range of businesses and programs" run by the buying groups.
The buying group, however, is convinced it has not overpaid.