Glossary of HIV/AIDS Terms
This glossary contains 1,600 terms and is maintained by the editors of the San Francisco AIDS Foundation's Bulletin of Experimental Treatments for AIDS.
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obesity: abnormal accumulation of fat either in the subcutaneous tissues or surrounding the visceral organs; excessive body weight. Typically, obesity refers to a body weight 20-30% above normal or a body mass index (BMI) of 30 kg/m2 or higher.
observational study: a clinical trial in which no experimental drug is administered, but subjects’ symptoms, laboratory values, and response to therapy are observed during the course of normal medical management.
obstetrics: the medical specialty concerned with pregnancy and birth.
occult: hidden or concealed.
ocular: refers to the eye or to vision.
odds ratio (acronym OR): a statistical measure of the likelihood of developing a disease or condition if a certain factor (e.g., pathogen, drug) is present.
off-label: use of a drug for an indication other than that for which it was approved.
OI: See opportunistic illness.
oligo-: prefix meaning few.
oncogen: an agent (e.g., virus, toxin) that can cause cancerous cell growth; oncogenesis refers to the development of cancer.
oncology: the medical specialty concerned with cancer and its treatment.
onychomycosis: a fungal infection that causes the toenails and/or fingernails to thicken, discolor, and split.
open-label: refers to a clinical trial that is not blinded; both participants and investigators know which drug is being tested and what dosages are being used.
ophthalmic: refers to the eye.
ophthalmology: the medical specialty concerned with the eye and its disorders.
opiate: a drug (e.g., codeine, heroin, morphine) derived from the opium poppy plant; an opioid is a synthetic drug (e.g., methadone) that has opiate-like effects. Opiates relieve pain, reduce cough, alter the mood, and induce sleep; they are typically habit-forming.
opportunistic illness (acronym OI, aka opportunistic infection): a condition that is not typically seen in people with healthy immune systems, but which can cause serious disease when the immune system is weakened; OIs in people with progressive HIV disease may include infections such as Pneumocystis carinii pneumonia (PCP), Mycobacterium avium complex (MAC), and cytomegalovirus (CMV), as well as cancers such as Kaposi?s sarcoma.
oral: refers to the mouth; taken by mouth.
oral candidiasis (aka thrush): a fungal infection of the mouth, usually caused by Candida albicans, which typically appears as white or red patches on the tongue or palate; types include pseudomembranous candidiasis, atrophic candidiasis, and angular cheilitis.
oral hairy leukoplakia: a condition, believed to be caused by the Epstein-Barr virus, characterized by white, raised, usually painless lesions on the sides of the tongue or elsewhere in the mouth.
organelle: a tiny, specialized organ (e.g., mitochondrion) within a cell.
osteoblast: a bone-forming cell. Contrast with osteoclast.
osteocalcin (aka bone GLA protein, aka BGP): the major noncollagenous protein of the bone matrix, synthesized by osteoblasts; osteocalcin in the blood is a marker of bone formation.
osteoclast: a cell involved in the absorption of bone and removal of bone tissue. Contrast with osteoblast.
osteomyelitis: inflammation of the bone and bone marrow.
osteopenia: reduced bone mass or bone mineral density. See also osteoporosis.
osteoporosis: severely reduced bone mass or bone mineral density; atrophy of bone tissue. Osteoporosis is associated with a high risk of bone fractures. See also osteopenia.
OTC: See over-the-counter.
outbreak: recurrence of a latent infection (e.g., a herpes zoster outbreak); the widespread occurrence of a disease within a population.
outpatient: an individual who is treated outside a hospital or other medical facility.
ovary: one of the two female gonads located within the abdomen on either side of the uterus; the ovaries are the site of ova (egg) storage and maturation.
over-the-counter (acronym OTC): refers to drugs that are available without a prescription.
ovulation: release of an ovum (egg) from an ovary.
oxidative stress: an increased level of free radicals and other oxidation-promoting molecules associated with disease, immune activation, and/or aging.
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