It is a review of a procedure or hospital admission done by a health care professional (usually a nurse) other than the one providing the care, during the same time frame that the care is provided. Usually conducted during a hospital confinement to determine the appropriateness of hospital confinement and the medical necessity for continued stay.

It is health coverage that a new enrollee has had in the past that gives the enrollee certain rights when he or she applies for new coverage. Certain kinds of previous health insurance coverage, such as group plan coverage, that can be used to shorten a pre-existing condition waiting period under a new plan.

Doctors in recent years have admitted to and have been accused of prescribing additional tests or procedures to justify their care, strengthen support for their decisions or simply to corroborate their diagnosis. This defensiveness is a result of lawsuits, malpractice claims and the onslaught of external UR entities questioning care decisions. Defensive medicine is said to be one of the primary causes of the increasing cost of health care. Many physicians and the AMA fight for tort reform to reduce the need for defensive medicine. However, patient groups and patient advocates, not in favor of tort reform, explain that the right to sue for malpractice is a valid method of holding physicians accountable for mistakes made.

It is health services provided without the patient being admitted. Also called outpatient care. The services of ambulatory care centers, hospital outpatient departments, physicians' offices and home health care services fall under this heading provided that the patient remains at the facility less than 24 hours. No overnight stay in a hospital is required.

It is a system in which prices for health services and payment methods are the same, regardless of who is paying. For instance, in an all-payer system, federal or state government, a private insurer, a self-insured employer plan, an individual, or any other payer could pay the same rates. The uniform fee bars health care providers from shifting costs from one payer to another.

It is a method for establishing health insurance premiums whereby an insurer's premium is based on the age of individuals when they first purchased health insurance coverage. This is an older form of actuarial assessment.