very insurer shall provide coverage for emergency medical services, including prehospital services, to the extent necessary to screen and to stabilize an emergency medical condition. The insurer shall not require prior authorization of the screening services if a prudent layperson acting reasonably would have believed that an emergency medical condition existed. Prior authorization of coverage shall not be required for stabilization if an emergency medical condition exists. Payment of claims for emergency services shall be based on the retrospective review of the presenting history and symptoms of the covered person.