 As with all HMOs, this can be a problem for people who want to use out-of-network specialists or who are hospitalized and are forced to use out-of-network doctors while hospitalized.Many Medicare Advantage PPO plans permit a subscriber to use any physician or hospital without prior authorization, but at a somewhat higher expense.If a patient's in-network physician orders tests or procedures or refers a patient to a specialty that are not available from an in-network provider, the plan pays for the patient's procedures or services at an out-of-network location and charges in-network rates to the patient, so long as the necessary services are normally covered by the plan (the beneficiary must still obtain authorization).