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Glossary of HIV/AIDS Terms

for Health Care Providers

Glossary of HIV/AIDS Terms


The lowest point. For example, a patient's CD4 nadir is that person's lowest measured CD4 count.

National Institutes of Health (NIH)

In the United States, a multi-institute agency of the U.S. Department of Health and Human Services. NIH is the federal focal point for health research. It conducts research in its own laboratories and supports research in universities, medical schools, hospitals, and research institutions throughout the United States and abroad. Internet address: will take you outside the VA website.

Natural history study

Study of the natural development of something (such as an organism or a disease) over a period of time.

Natural killer (NK) cells

A type of lymphocyte.


See Aerosolized.


Concerning the first 6 weeks of life after birth.


An abnormal and uncontrolled growth of tissue; a tumor.


Poisonous to the kidneys.


A sharp, shooting pain along a nerve pathway.


Related to the brain, spinal cord, or nerves.

Neurological complications of AIDS

See Central nervous system (CNS).


The name given to a group of disorders involving nerves. Symptoms range from a tingling sensation or numbness in the toes and fingers to paralysis.

See Peripheral neuropathy.


The process by which an antibody binds to specific antigens, thereby "neutralizing" the microorganism.

Neutralizing antibody

An antibody that keeps a virus from infecting a cell, usually by blocking receptors on the cell or the virus.


An abnormal decrease in the number of neutrophils (the most common type of white blood cell) in the blood. The decrease may be relative or absolute. Neutropenia may be associated with HIV infection or may be drug induced.


A type of white blood cell (leukocyte) that engulfs and kills foreign microorganisms such as bacteria.

Non-Hodgkin lymphoma (NHL)

A lymphoma made up of B cells and characterized by nodular or diffuse tumors that may appear in the stomach, liver, brain, and bone marrow of persons with HIV. After Kaposi sarcoma, NHL is the most common opportunistic cancer in persons with AIDS.

Non-nucleoside reverse transcriptase inhibitor (NNRTI)

A group of compounds that bind to the catalytic site of HIV-1's reverse transcriptase and block HIV replication.


A classification of drugs called nonsteroidal antiinflammatory drugs. NSAIDs reduce inflammation and are used to treat arthritis and mild-to-moderate pain.

Nucleic acid amplification testing

See Nucleic acid test.

Nucleic acid test

A technology that allows detection of very small amounts of genetic material (DNA or RNA) in blood, plasma, and tissue. A nucleic acid test can detect any number of viruses in blood or blood products, thereby better assuring the safety of the blood supply.


A building block of nucleic acids, DNA, or RNA, the genetic material found in living organisms. Nucleosides are nucleotides without the phosphate groups.

Nucleoside analogue

An artificial copy of a nucleoside. When incorporated into the DNA or RNA of a virus during viral growth, the nucleoside analogue acts to prevent production of new virus.

Nucleoside reverse transcriptase inhibitor (NRTI)

A nucleoside analogue antiretroviral drug whose chemical structure constitutes a modified version of a natural nucleoside. These compounds suppress replication of retroviruses by interfering with the reverse transcriptase enzyme. The nucleoside analogues cause premature termination of the proviral (viral precursor) DNA chain.


Nucleotides are the building blocks of nucleic acids, DNA, and RNA. Nucleotides are composed of phosphate groups, a five-sided sugar molecule (ribose sugars in RNA, deoxyribose sugars in DNA), and nitrogen-containing bases.

Nucleotide analogue

Nucleotide analogues are drugs that are structurally related to nucleotides; they are chemically altered to inhibit production or activity of disease-causing proteins.


The central controlling body within a living cell, usually a spherical unit enclosed in a membrane and containing genetic codes for maintaining the life systems of the organism and for issuing commands for growth and reproduction.