The Affordable Care Act enshrines a hope—that doctors, hospitals and other providers will team up to improve patient care and reduce costs. But there’s also a fear—that doctors, hospitals and other providers will team up to stifle competition and raise prices instead.

Creating so-called accountable care organizations, or ACOs, is a key element of health care reform. Making sure that these collaborative networks don’t hurt competition has fallen to the Federal Trade Commission and the Department of Justice’s Antitrust Division.