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Glossary of HIV/AIDS Terms

for Health Care Providers

Glossary of HIV Terms

P24 antigen

A bullet-shaped part of a protein that surrounds the viral RNA within the envelope of HIV. The p24 antigen test (which is included in the fourth-generation Ag/Ab HIV test) looks for the presence of this protein in a patient's blood. A positive result for the p24 antigen suggests active HIV multiplication.

Package insert

A document, approved by the FDA and furnished by the manufacturer of a drug (inserted into the package), for use when dispensing the drug. The document indicates approved uses, contraindications, and potential side effects.


A treatment that provides symptomatic relief but not a cure.

Palliative care

Palliative care is an approach to life-threatening chronic illnesses, especially at the end of life. Palliative care combines active and compassionate therapies to comfort and support patients who are living with life-ending illnesses and their families. Palliative care strives to meet physical needs through relieving pain and maintaining quality of life while emphasizing the patient's and family's rights to participate in informed discussions and to make choices. This patient- and family-centered approach uses the skills of interdisciplinary team members to provide a comprehensive continuum of care, including spiritual and emotional needs.


Deficiency of all cell elements of the blood.


A disease prevalent throughout an entire country or continent, or the whole world.

See Epidemic.

Pap smear

A method for the early detection of cancer and other abnormalities of the anogenital tract, especially of the cervix and anus.


A benign tumor (as a wart, condyloma, or polyp) resulting from an overgrowth of epithelial tissue. An epithelial tumor caused by a virus.

See Condyloma; Epithelium; JC virus.


A plant or animal that lives and feeds on or within another living organism (host), causing some degree of harm to the host organism.


A route other than in or through the digestive system. For example, parenteral can pertain to blood being drawn from a vein in the arm or introduced into that vein via a transfusion (intravenous), or to injection of medications or vaccines through the skin (subcutaneous) or into muscle (intramuscular).


Abnormal sensations such as burning, tingling, or a "pins-and-needles" feeling. Paresthesia may constitute the first group of symptoms of nerve involvement in HIV infection.


Any disease-producing microorganism or material.


The origin and development of a disease.

Pelvic inflammatory disease (PID)

Gynecological condition caused by an infection (usually sexually transmitted) that spreads from the vagina to the upper parts of a woman's reproductive tract in the pelvic cavity. PID takes different courses in different women, but can cause abscesses and constant pain almost anywhere in the genital tract. If left untreated, it can cause infertility or more frequent periods.


Around the anus.


Pertaining to or occurring in the period shortly before and after birth, variously defined as beginning with completion of the 20th to 28th week of gestation and ending 7 to 28 days after birth.

Perinatal transmission

Transmission of a pathogen, such as HIV, from mother to baby before, during, or after the birth process.


See Perinatal.

Peripheral neuritis

Inflammation of far portion of the nerves or the nerve endings, usually associated with pain, muscle wasting, and loss of reflexes.

Peripheral neuropathy

Condition characterized by sensory loss and often pain in the hands or legs and feet. It may start with burning or tingling sensations or numbness in the toes and fingers. In severe cases, muscle weaknesss may be present. Peripheral neuropathy may arise from an HIV-related condition or be the side effect of certain drugs, some of the older nucleoside analogues in particular.

Persistent generalized lymphadenopathy (PGL)

Chronic, diffuse, noncancerous lymph node enlargement. Typically it has been found in persons with persistent bacterial, viral, or fungal infections. PGL in HIV infection is a condition in which lymph nodes are chronically swollen in at least two areas of the body for 3 months or more with no obvious cause other than the HIV infection.


A cell that is able to ingest and destroy foreign matter, including bacteria.


The process of ingesting and destroying a virus or other foreign matter by phagocytes.

See Macrophage; Monocyte.


The processes (in a living organism) of absorption, distribution, metabolism, and excretion of a drug or vaccine.


The genetic makeup of an organism such as HIV as it interacts with the environment. In the case of HIV, the virus may interact with cells and drugs. Phenotypic resistance testing determines whether an organism is susceptible to a specific drug in a test tube. Contrast with genotype.


A substance that has no activity, often used in a clinical study so that participants do no know if they are receiving the active (study drug) or the inactive placebo. This approach assists in performing clinical studies and determining whether a drug is active against a disease.

Placebo effect

A physical or emotional change, occurring after a substance is taken or administered, that is not the result of any special property of the substance. The change may be beneficial, reflecting the expectations of the patient and, often, the expectations of the person giving the substance.

Placebo-controlled study

A method of investigation of drugs in which an inactive substance (placebo) is given to one group of patients, while the drug being tested is given to another group. The results obtained in the two groups are then compared to see if the investigational treatment is more effective in treating the condition.


The liquid part of the blood and lymph that contains nutrients, electrolytes (dissolved salts), gases, albumin, clotting factors, wastes, and hormones.


Active agents of inflammation that are released when damage occurs to a blood vessel. The platelets stick to the blood vessel walls, forming clots to prevent the loss of blood. Some persons living with HIV develop thrombocytopenia, a condition characterized by a platelet count of <100,000 platelets per cubic millimeter of blood.


People living with HIV/AIDS.


People living with HIV/AIDS.


Prevention of mother-to-child transmission (of HIV).

Pneumocystis jiroveci pneumonia (PCP, PJP)

An infection of the lungs caused by Pneumocystis jiroveci, which is thought to be a protozoan but may be more closely related to a fungus. P jiroveci grows rapidly in the lungs of persons with AIDS and is a frequent AIDS-related cause of death. P jiroveci infection sometimes may occur elsewhere in the body (skin, eye, spleen, liver, or heart).

Polymerase chain reaction (PCR)

A laboratory process in which a DNA segment is selected from a mixture of DNA chains and rapidly multiplies to create a large sample of a piece of DNA. It is a sensitive laboratory technique that can detect and measure HIV in a person's blood or lymph nodes (also called RT-PCR). It also is a means of measuring the amount of virus in the blood (viral load).


Inflammation of many nerves at once.

Polyvalent vaccine

A vaccine that is active against multiple viral strains.

Positive test result

Any result that indicates that a person has a disease or infection. For HIV, a positive test result indicates that the person has been infected with HIV.

Postexposure prophylaxis (PEP)

As it relates to HIV disease, a potentially preventative treatment using antiretroviral drugs to treat individuals within 72 hours of a high-risk exposure (e.g., needlestick injury, unprotected sex, needle sharing) to prevent HIV infection.


Occurring after birth, especially during the period immediately after birth.


See Postnatal.

Preconception counseling

Recommended for all women of childbearing age as a component of their primary medical care. The purpose of preconception care is to identify risk factors for adverse maternal or fetal outcome, provide education and counseling targeted to the patient's individual needs, and treat or stabilize medical conditions prior to conception in order to optimize maternal and fetal outcomes.

Preexposure prophylaxis (PrEP)

In reference to HIV, a medication given before exposure to HIV in order to prevent infection. The PrEP medications are Truvada and Descovy.


The period preceding birth, during which the fetus develops in the uterus.


See Prenatal.


A measure of the proportion of people in a population affected with a particular disease at a given time.

Primary HIV infection

See Acute HIV infection.

Primary isolate

HIV taken from an infected individual (as opposed to being grown in laboratory cultures).


The chance, or likelihood, that a certain event will occur.


Inflammation of the rectum.


A symptom that indicates the onset of a disease.

Progressive multifocal leukoencephalopathy (PML)

A rapidly debilitating opportunistic infection caused by the JC virus that infects brain tissue and causes damage to the brain and the spinal cord. Symptoms vary from patient to patient but include loss of muscle control, paralysis, blindness, problems with speech, and an altered mental state. PML can lead to coma and death.

Prophylactic drug

A drug that helps to prevent a disease or initial infection.

See Prophylaxis.


Treatment to prevent the onset of a particular disease (primary prophylaxis), or the recurrence of symptoms in an existing infection that has been brought under control (secondary prophylaxis, maintenance therapy).


An enzyme that breaks down proteins into their component peptides. HIV's protease enzyme breaks apart long strands of viral protein into the separate proteins making up the viral core. The enzyme acts as new virus particles are budding off a cell membrane. Protease is the first HIV protein for which a three-dimensional structure has been characterized.

Protease inhibitor

A class of antiviral drugs that act by inhibiting the virus' protease enzyme, thereby preventing viral replication. Specifically, these drugs block the protease enzyme from breaking apart long strands of viral proteins to make the smaller, active HIV proteins that comprise the virion. If the larger HIV proteins are not broken apart, they cannot assemble themselves into new functional HIV particles.

Protease-sparing regimen

An antiretroviral drug regimen that does not include a protease inhibitor.


The detailed plan for conducting clinical studies. It states the trial's rationale, purpose, drug or vaccine dosages, length of study, routes of administration, who may participate (Inclusion/Exclusion Criteria), and other aspects of trial design.

See Inclusion/Exclusion criteria.


Large group of one-celled (unicellular) animals, including amoebas. Some protozoa cause parasitic diseases in persons with AIDS, notably toxoplasmosis and cryptosporidiosis.

See Pneumocystis jiroveci pneumonia (PCP, PJP).

Purified protein derivative (PPD)

Material used in the tuberculin skin test (TST); a common test for exposure to Mycobacterium tuberculosise bacterium that causes tuberculosis (TB). PPD is sometimes used synonymously with TST. In the PPD test, a small amount of protein from TB is injected under the skin. If patients have been previously infected, they will mount a delayed-type hypersensitivity reaction, characterized by a hard, red bump called an induration.


A person who injects drugs. People who inject drugs.