California’s biggest health insurers reported inaccurate information to the state on which doctors are in their networks, offering conflicting lists that differed by several thousand physicians, according to a new state report.

Shelley Rouillard, director of the California Department of Managed Health Care, said 36 of 40 health insurers she reviewed — including industry giants like Aetna and UnitedHealthcare — could face fines for failing to submit accurate data or comply with state rules.

Rouillard said she told health plan executives in a meeting last week that such widespread errors made it impossible for regulators to tell whether patients have timely access to care in accordance with state law.

“I told the CEOs it looks to me like nobody cared. We will be holding their feet to the fire on this,” Rouillard said in an interview with California Healthline. “I am frustrated with the health plans because the data we got was unacceptable. It was a mess.”

The state wasn’t assessing the accuracy of online provider directories that are used by consumers. But the new report suggests that insurers may be misrepresenting which providers they have under contract or are unable to collect accurate information.

Flawed provider directories are a longstanding problem industrywide, and the proliferation of narrow networks on the Obamacare insurance exchanges and in employer health plans has sparked numerous consumer complaints.

Outdated and inaccurate provider lists can hinder patients from getting treated and, in some cases, lead to huge unforeseen medical bills when people unwittingly go out of network for care.

California officials discovered the latest problems while reviewing annual reports filed by insurers. In those reports, insurers submitted two sets of provider lists, one used during the year to measure patient access and the other a year-end tally. Often they were dramatically different.

UnitedHealthcare, the nation’s largest health insurer, listed 9,135 primary-care doctors on the provider list used during the year who were absent from year-end list — a discrepancy of 45 percent.

Cigna, another big insurer, named 8,572 on the one list who were not on the other, a 36 percent discrepancy. For Anthem Blue Cross, the discrepancy was 8,165 primary-care physicians, or 36 percent, and for Blue Shield of California it was 4,371 primary-care doctors, or 22 percent.

In another instance, the state said Aetna counted the same cardiologists in one county more than 160 times, inflating the number of specialists overall by 2,293. That overstated the list of specialists by 82 percent.

Overall, for seven insurers, the two sets of lists differed by 50 percent or more for in-network specialists.

Rouillard said provider directories can fluctuate over time, so some small variations between one list used during the year and another at year’s end would be expected. But she said the wildly different figures that were reported raised red flags and made it impossible to know whether enough doctors were available to see patients.

Some of these issues are not new. In 2015, California’s managed care agency fined Anthem $250,000 and Blue Shield of California $350,000 for overstating the breadth of their doctor networks.

Both Anthem and Blue Shield of California declined to comment on the state’s most recent findings. Aetna said it was still reviewing the state’s analysis.

Other health insurers referred questions to an industry trade group. Charles Bacchi, chief executive of the California Association of Health Plans, said some mistakes may have been made but emphasized that measuring patient access to physicians is difficult.

“Health plans are committed to providing timely access to health care and we believe that we provide that successfully,” Bacchi said. “Clearly this report demonstrates that we have work to do to improve our survey responses, and health plans are committed to working with the department to address it.”

Under California law, patients must get urgent care appointments within 48 to 96 hours. Primary-care visits must be scheduled within 10 business days and appointments with a specialist must come within 15 business days.

Yet many consumers continue to struggle to find in-network doctors to meet their needs.

David Discher of Redwood City, Calif., said he tried most of last year to find doctors who would take his Anthem Blue Cross insurance. The 39-year-old suffers from psoriatic arthritis and requires regular infusion treatments.

The Anthem directory for consumers listed three rheumatologists in his area. One doctor’s phone was disconnected and the other two were no longer accepting his Anthem plan, Discher said. His joint pain and swelling worsened while he waited nearly two months to see a specialist.

“It boggles my mind that insurers can’t keep their list up to date,” Discher said. “There is no excuse for how messy it is. Health insurers are engaged in false advertising.”

Consumer outrage over provider directories led to passage of a state law last year that requires insurers and medical providers to ensure the lists are accurate and regularly updated. It also requires health plans to reimburse consumers who are charged out-of-network prices because of an inaccurate provider list.

This latest review by regulators stemmed from a 2014 law sponsored by state Sen. Ed Hernandez (D-West Covina) that required insurers file reports to the state to combat problems with provider lists and barriers to care. He and consumer advocates urged regulators to step up enforcement against insurers that are violating the law.

“Their inability to accurately document which providers are in their networks raises serious questions about the reliability of these networks,” said Hernandez, chairman of the Senate Health Committee.

The state report analyzed data for 2015, and it applied to people in employer plans, individual policies and Medicaid.

Only four health plans submitted information without substantial errors. Two were full-service health plans, Community Health Group and Inland Empire Health Plan. The two others specialize in behavioral health: Human Affairs International of California and Managed Health Network.

The next round of reports from insurers on patient access and provider lists are due next month.

This story was produced by Kaiser Health News, which publishes California Healthline, an editorially independent service of the California Health Care Foundation.