Most HMOs require members to select a primary care physician (PCP), a doctor who acts as a "gatekeeper" to limit access to medical services. PCPs are usually internists, pediatricians, family doctors, or general practitioners (GPs). Absent a medical emergency, patients need a referral from the PCP in order to see a specialist or other doctor, and the gatekeeper cannot authorize that referral unless the HMO guidelines deem it necessary.
"Open access" HMOs do not use gatekeepers - there is no requirement to obtain a referral before seeing a specialist. The beneficiary cost sharing (e.g., co-payment or coinsurance) may be higher for specialist care, however.
HMOs also manage care through utilization review. That means they monitor doctors to see if they are performing more services for their patients than other doctors, or fewer. HMOs often provide preventive care for a lower copayment or for free, in order to keep members from developing a preventable condition that would require a great deal of medical services. When HMOs were coming into existence, indemnity plans often did not cover preventive services, such as immunizations, well-baby checkups, mammograms, or physicals. It is this inclusion of services intended to maintain a member's health that gave the HMO its name. Some services, such as outpatient mental health care, are limited, and more costly forms of care, diagnosis, or treatment may not be covered. Experimental treatments and elective services that are not medically necessary (such as elective plastic surgery) are almost never covered.
Other Choices for managing care are case management, in which patients with catastrophic cases are identified, or disease management, in which patients with certain chronic diseases like diabetes, asthma, or some forms of cancer are identified. In either case, the HMO takes a greater level of involvement in the patient's care, assigning a case manager to the patient or a group of patients to ensure that no two providers provide overlapping care, and to ensure that the patient is receiving appropriate treatment, so that the condition does not worsen beyond what can be helped.
HMOs often shift some financial risk to providers through a system called capitation. Certain providers (usually PCPs) receive a fixed payment per member per month in exchange for providing certain services, creating an incentive to provide as little care as possible. To counterbalance this trend some plans offer a bonus to providers whose care meets a predetermined level of quality.
Some critics regard HMOs as monopolies that distort the market for health care.
In 1970, the number of HMOs declined to less than 40. Paul Ellwood, often called the "father" of the HMO, began having discussions with what is today the U.S. Department of Health and Human Services that led to the enactment of the Health Maintenance Organization Act of 1973. This act had three main provisions:
This last provision, called the dual choice provision, was the most important, as it gave HMOs access to the critical employer-based market that had often been blocked in the past. The federal government was slow to issue regulations and certify plans until 1977, when HMOs began to grow rapidly. The dual choice provision expired in 1995.
In 1971, Dr. Gordon K MacLeod MD developed and became the director of the United States' first federal Health Maintenance Organization (HMO) program. He was recruited by Elliot Richardson, former secretary of the U.S. Department of Health, Education and Welfare.
In the staff model, physicians are salaried and have offices in HMO buildings. In this case, physicians are direct employees of the HMOs. This model is an example of a closed-panel HMO, meaning that contracted physicians may only see HMO patients.
In the group model, the HMO does not employ the physicians directly, but contracts with a multi-specialty physician group practice. Individual physicians are employed by the group practice, rather than by the HMO. The group practice may be established by the HMO and only serve HMO members ("captive group model"). Kaiser Permanente is an example of a captive group model HMO rather than a staff model HMO, as is commonly believed. An HMO may also contract with an existing, independent group practice ("independent group model"), which will generally continue to treat non-HMO patients. Group model HMOs are also considered closed-panel, because doctors must be part of the group practice to participate in the HMO - the HMO panel is closed to other physicians in the community.
Physicians may contract with an independent practice association (IPA), which in turn contracts with the HMO. This model is an example of an open-panel HMO, where a physician may maintain their own office and may see non-HMO members.
In the network model, an HMO will contract with any combination of groups, IPAs, and individual physicians. Since 1990, most HMOs run by managed care organizations with other lines of business (such as PPO, POS and indemnity) use the network model.
Primary care doctor: In most HMOs you must have a main doctor, called a primary care physician, or PCP. This doctor gives you most of your care and refers you for other services when you need them. Usually, you must see this doctor first before you can see a specialist. Your primary care doctor must be in the HMO’s network.
Medical group: Your medical group is the group of doctors and other providers that your primary care doctor is in. The medical group has a contract with the HMO to provide your care.
Networks and medical groups: Each HMO has a network of doctors, medical groups, labs, hospitals, and other providers who work for the HMO or have a contract with it. You must get approval from your HMO to get care from a provider outside the network, unless it’s an emergency, or you need urgent care and are outside your plan’s area. Most of the providers you see are also in your medical group. Ask the plan to mail you a copy of its provider directory. Or look on the plan’s website.
Referrals and pre-approval: You must have a referral to see a specialist or get most other services. Your HMO or medical group must approve many of your services before you can get them. Usually it is your doctor who gives you a referral and asks for pre-approval.
HMOs are regulated at both the state and federal levels. They are licensed by the states, under a license that is known as a certificate of authority (COA) rather than under an insurance license. In 1972 the National Association of Insurance Commissioners adopted the HMO Model Act, which was intended to provide a model regulatory structure for states to use in authorizing the establishment of HMOs and in monitoring their operation.