Minnesota health care leaders barely had a chance to play with their new toy — the all-payer claims database that definitively shows what Minnesotans spend on health care — and already it is being taken away.

A U.S. Supreme Court ruling imperiled these databases in 18 states by finding that state governments cannot require self-insured employers to share information to them.

In Minnesota, that would carve out 38 percent of residents, who receive their benefits from big companies such as Carlson and Target. (Self-insured means companies bear the entire risk and cost of their workers' medical needs, rather than letting their insurer carry the risk.)

That's a big gap in a database designed to resolve some vexing questions, such as which patients cost most, which parts of the state are most expensive, and whether minority members receive proportionate medical care.

"If all Minnesota self-insured employers decided to stop submitting data, it … could make certain types of analyses less reliable," said Michael Schommer of the Minnesota Department of Health.

Researchers have only touched the database's potential. State leaders in January offered a first-of-its-kind comparison of health care spending, and found that chronically ill Minnesotans were eight times more expensive than healthy ones.

The comparison also found regional gaps: the typical kidney failure patient cost $24,690 in Houston County in 2012, but $50,760 in Stevens County.

"Hopefully in the future, we can drill down to figure out what's driving cost differences and help our residents be better consumers of health care," Isanti County Commissioner Susan Morris, said at the time.

The future of the database was already in question, because of the need for state lawmakers to reauthorize its funding amid calls from privacy advocates to eliminate it.

Following the high court announcement, local medical privacy advocate Twila Brase declared a victory for privacy and called on states with these databases to dismantle them.

The state Health Department isn't giving up so easily. Schommer said the department expects new funding for the database, and that many large self-insured companies in Minnesota have supported health care reforms and might simply donate their claims data. (The data is scrubbed of any identifying information.)

Changes in federal law also could address the problems that prompted the ruling.

jeremy.olson@startribune.com • 612-673-7744 @StribJO