MINNEAPOLIS-Some big employers here want to reform a health-care delivery system they see as outmoded, inefficient, and riddled with perverse incentives. So they’ve renounced HMOs.   In January the 25 firms in the Buyers Health Care Action Group will shift at least 100,000 people into a new kind of plan. It replaces negotiations between the companies and giant HMOs with a form of direct-contracting system. In it, employees shop for the best cost and quality among 15 full-service care systems, each with its pluses and minuses.   Steve Wetzell, executive director of the group, says the managed-competition-like approach will stir up a market that’s stagnant from consolidation, reward doctors for efficiency, quality, and service, and let patients make meaningful choices.   The experiment has garnered nationwide attention as firms seek to improve on traditional managed care. Already it has brought rates that are 5% below those of HMOs. Wetzell says it has won praise from the Minnesota Medical Association and the AMA, which see the approach as a way to put providers back in control and bolster the relationship between doctor and patient.   But skeptics say the “consumer-choice” model faces major challenges, such as transforming naive consumers into savvy health-care buyers.   The model evolved here as mergers and buyouts left the Twin Cities with just four major health plans and great overlap in provider networks. Wetzell says the remaining players have tended to price their products similarly, while their size has discouraged new competition.   Plan-shifting had come to mean little for physician or patient, says Wetzell. Because doctors belonged to several plans, they rarely lost patients in a switch. And because the HMOs aren’t heavily capitated, providers had little stake in efficiency.   The new effort tries to change all that by having employers contract directly with each care system while maintaining a single administrative system and common rules. This farmers’ market approach-employees pick the firmest ripe tomatoes, or the cheapest, or an amalgam-eases paperwork for employers and puts key decisions in the hands of patients.   Primary-care physicians may join only one of the systems, though specialists aren’t limited. Each system is assigned to a cost tier based on its bid and claims history. So when consumers choose one, they are deciding which primary-care doctors they’ll get and how much above an employer’s fixed contribution they’ll pay.   Employers must offer a standard benefit package, though they may add others. To encourage wise choices, consumers can look up computerized details about such things as physician credentials and clinic hours. There will also be data on clinical quality indicators and patient satisfaction.   Care systems are paid for services on a fee schedule derived from the risk-adjusted spending targets. If a system is under target for one quarter, fees go up the next. Above the target, they go down. This obviates regulatory requirements of insurers.   Though still untested, the experiment has sent reverberations through the Twin Cities market and beyond. Care systems are being operated not only by physicians and hospitals, but by local HMOs. In turn, the 15 care systems have recruited 95% of local physicians, Wetzell says. And the project has prompted imitation.   HealthPartners-a major player that worked with the business group on the consumer choice model and will administer it-is launching a similar offering of its own in 1997. The plan will allow provider groups within the HealthPartners network to compete by assigning them to one of several cost tiers and letting consumers choose.   Blue Cross is working on a plan to offer a “core network” of providers that would be cheaper than its full network, says VP Susan Flygare.   And in Iowa, the Community Health Purchasing Corporation is implementing the model on a smaller scale. It has three care systems signed up, and hopes for a dozen statewide.   The changes may signal an era in which employers are more involved in providing information and less in selecting a provider network, says Jack Meyer, president of the Economic and Social Research Institute in Washington. “They want to move employees into the driver’s seat.”   But that may prove difficult, says Dr. John Kralewski, director of the Institute for Health Services Research at the University of Minnesota. He says consumers typically choose the cheapest option and may try to avoid changing doctors, but they rarely make more sophisticated decisions.   Dr. Kralewski says another problem is adverse selection, which could sink care systems without large numbers of patients. But Wetzell believes that a sophisticated risk-adjustment system will prevent that.   Blue Cross thinks the new model may just divert attention from such issues as reducing capacity and practice variations. Moreover, “direct contracting does not make administrative systems go away” and even adds a new layer of management, says Flygare. She also predicts the economies of scale will lead to consolidation among the 15 care systems in a fate similar to that of the HMOs.   But even if the consumer-choice model is less than a panacea, it has shown the value of involving consumers in health-care decisions, says Pamela Lux, a VP at HealthPartners. For instance, when clinics saw patients were learning about operating hours, many stayed open nights and weekends. -Jon Hamilton