CONCORD, N.H. — An initial review of whether health insurance companies are appropriately covering substance abuse treatment in New Hampshire shows significant differences in how often claims are denied, but experts identified problems with only a handful of cases.

The probe comes as New Hampshire seeks to expand treatment and recovery services amid a growing heroin and opioid crisis. The state insurance department began looking into the issue in November after hearing complaints from providers and advocates, and officials presented their preliminary findings in Concord on Friday.

From January to October, there were 11,650 claims for opioid treatment among the top three insurance companies – Anthem Blue Cross and Blue Shield, Cigna and Harvard Pilgrim – and across the board, the number of patients filing such claims represented less than half of one percent of each company’s customers.

The companies weren’t identified individually, but their denial rates for opioid treatment claims were 9.5 percent, 15 percent and 28.3 percent. Medical experts reviewed 64 cases in which treatment was deemed medically unnecessary and had concerns with just eight of them.

Among those eight, most were not outright denials but involved disagreements about the level of care requested, Deputy Insurance Commissioner Alex Feldvebel told the Governor’s Commission on Alcohol and Drug Abuse Prevention, Intervention and Treatment.

“We think maybe there’s a lack of understanding about the need for short-term inpatient withdrawal management services versus indefinite inpatient treatment,” he said.

Officials also reviewed each insurer’s provider network and the appeals process available to consumers. The network review found that service in the state’s northern most county, Coos, was a challenge, but there was no shortage in the most populous southern counties – Rockingham and Hillsborough – and some gaps elsewhere across the state.

They found no problems with the appeals processes but said few consumers made use of them. Similarly, the insurance department received only a handful of consumer complaints or requests for external reviews in the last several years.

Members of the commission said those numbers likely reflect how difficult it can be to navigate the insurance system in general, let alone for someone dealing with drug addiction.

“There may be a no more health literacy-challenged population than someone in the throes of an active behavioral health disorder,” said commission chairman Timothy Rourke. “It can be an overwhelming situation, and for this population even more so.”

The insurance department will continue its review to assess whether companies are handling substance abuse treatment claims on par with medical and surgical claims as required under the Affordable Care Act. A final report is expected next summer.