GAO made the following findings.
Application denials varied widely. While the aggregate rate was 19 percent, about one quarter of insurers had rates from 0-15 percent while another quarter had rates of 40 percent or more.
Denials for preauthorizations and claims also varied. Aggregate rates in three states ranged from 11-24 percent and rates across insurers 6-40 percent in one state.
Appeals were frequently reversed. In four states, 39-59 percent of appeals resulted in the reversal of an original coverage denial. And appeals in an independent, external review brought about a reversal about 40 percent of the time.
Read the GAO report on health insurers.
Read more coverage of denials of insurance coverage: