When legislators in Texas demanded some data from insurers last year, they learned that up to half of the hospitals that participated with UnitedHealthcare, Humana and Blue Cross-Blue Shield — Texas’s three biggest insurers — had no in-network emergency room doctors. Out-of-network payments to emergency room physicians accounted for 40 to 70 percent of the money spent on emergency care at in-network hospitals, researchers with the Center for Public Policy Priorities in Austin found.

“It’s very common and there’s little consumers can do to prevent it and protect themselves — it’s a roll of the dice,” said Stacey Pogue, a senior policy analyst with the nonpartisan center and an author of the study.

While patients have complained of surprise out-of-network charges in hospitals from some other specialists — particularly anesthesiologists, radiologists and pathologists — the situation with emergency room doctors is even more troubling, patient advocates say. For one thing, patients cannot be expected to review provider networks in a crisis, and the information to do so is usually not readily available anyway. Moreover, the Texas study found that out-of-network fees paid to emergency room physicians eclipsed the amount of money paid to those other specialists.