Most of the formularies run by some of the largest health plans in the U.S. generally provide “fair access” to 18 treatments for a handful of serious diseases, although transparent coverage information is often lacking for some medicines, a new analysis has found.

Almost uniformly, the 19 formularies made the medicines available fairly when judged on three criteria: eligibility based on clinical data, restrictions placed on prescribers, and step therapy, which requires patients to try other medicines before an insurer will approve a prescription. The formularies are run by health plans, pharmacy benefit managers, and the U.S. Department of Veterans Affairs.