The country's top-performing health systems are achieving better clinical and operational performance through more consistent care among member hospitals, according to the IBM Watson Health 15 Top Health Systems Study, 2018. The Watson Health 15 Top Health Systems study evaluates health system performance across nine clinical and operational performance benchmarks: risk-adjusted inpatient mortality index, risk-adjusted complications index, mean health care-associated infection index, mean 30-day risk-adjusted mortality rate, mean 30-day risk-adjusted readmission rate, severity-adjusted length of stay, mean emergency department throughput, Medicare spend per beneficiary index and HCAHPS score. Extrapolating the results of this year's study, if all Medicare inpatients were similarly situated and received the same level of care as those treated in the award-winning facilities: More than 60,000 additional lives could be saved; more than 31,000 additional patients could be complication-free; health care-associated infections would be reduced by 16 percent; and patients would spend 40 minutes less time in hospital emergency rooms per visit. The metrics may sound a little dry, but they're important--the health systems that excel in these areas are leading the transition from fee-for-service to outcome-based care and total population health management. Here are the 2018 top-performing health systems, by category:

Large Health Systems

Mayo Foundation – Rochester, Minnesota Mercy – Chesterfield, Missouri Sentara Healthcare – Norfolk, Virginia St. Luke's Health System – Boise, Idaho UCHealth – Aurora, Colorado

Medium Health Systems

Aspirus Network – Wausau, Wisconsin HealthPartners – Bloomington, Minnesota Mercy Health, Cincinnati – Cincinnati, Ohio Mission Health – Asheville, North Carolina TriHealth – Cincinnati, Ohio

Small Health Systems

Asante – Medford, Oregon CHI St. Joseph Health – Bryan, Texas Maury Regional Health – Columbia, Tennessee Roper St. Francis Healthcare – Charleston, South Carolina UPMC Susquehanna Health System – Williamsport, Pennsylvania