More than four years ago, the Wisconsin Collaborative for Healthcare Quality set out to compare its information on healthcare quality with Medicare claims data. The group was one of six nationwide chosen for the research project. "We thought it would be extraordinarily easy," said Amy Topel, who managed the project. "And it didn't turn on out to be." The same discovery could await similar groups in coming years. Last week, the Department of Health and Human Services said it will make its database on Medicare claims available to groups that track health care quality and cost.