A partnership between two rivals offers a glimpse of the future under a cornerstone of the federal health care overhaul. HealthPartners and Allina Hospitals and Clinics together tested strategies to improve care and reduce health costs for some 27,000 patients in the northwest metro area. The partnership calls the effort a "learning lab" for the Accountable Care Organization envisioned under the federal health care law. They say they've proven that such an organization can lower costs while improving quality. After a year, their collaboration saved about $6 million which was enough to bring the growth rate of health care costs down from 8 percent to just 3 percent, and improving patient satisfaction scores.