Access to health care
having the timely use of personal health services to achieve the best health outcomes
Accuracy the extent to which a measurement or study result correctly represents the characteristic or relationship that is being assessed
Acquired immunodeficiency syndrome (AIDS) a disease characterized by a marked reduction in CD4+ T lymphocytes and associated defects in immune response caused by the human immunodeficiency virus (HIV)
Active surveillance a system of data collection in which those responsible for collecting the information go into the community under observation (typically defined by geographic boundaries) to gather data from various sources
Acute a disease of short duration
Adaptive randomized controlled clinical trial an experimental study in which the collected data are used to guide predefined design adaptations when the trial is in progress
Adjustment a procedure for overall comparison of two or more populations in which background differences in the distribution of covariables are removed (see also Standardization)
Administrative data billing data or hospital discharge data that can be used for research on health-related questions, including costs of care
Age adjustment a procedure used to calculate summary rates for different populations in which underlying differences in the age distributions are removed (see also Age standardization)
Age-specific rate a rate (usually incidence or mortality) for a particular age group
Age standardization (direct) a procedure for obtaining a weighted average of age-specific rates in which the weights are selected on the basis of a standard age distribution (e.g., the population of the United States in 2000)
Alpha error see Type I error
Analytic epidemiology activities related to the identification of possible determinants of disease occurrence
Analytic study a research investigation designed to test a hypothesis, often used in reference to a study of an exposure-disease association
Antibody a protein, often produced in response to exposure to an antigen that binds to the antigen and thereby stimulates its inactivation by the immune system
Antigen a protein, usually foreign in origin, that is capable of generating an immune response in a host animal
Arithmetic mean see Mean
Arteriosclerosis hardening of the arteries
Association the extent to which the occurrence of two or more characteristics is linked either through a causal or noncausal relationship
Asymptomatic persons individuals who have a particular disease but do not manifest abnormalities of function, appearance, or sensation typically associated with that disease
Attack rate the proportion of persons within a population who develop a particular outcome within a specified period of time
Attributable risk percent the percentage of the overall risk of a disease outcome within exposed persons, related to the exposure of interest
Benign a mild illness; when applied to an abnormal growth of cells (i.e., a neoplasm), it connotes a slowly progressing defect that is not invading adjacent tissues (in contrast to the rapid growth and invasive behavior of a malignant neoplasm)
Beta error see Type II error
Bias a nonrandom error in a study that leads to a distorted result
Biologic marker (or biomarker) a ...