HIV

QD

Once each day.

QID

Four times each day.

Randomized trial

A study in which participants are randomly assigned to one of two or more treatment arms or regimens of a clinical study. Often, placebos are utilized.

See Placebo-controlled study.

Rapid HIV test

A screening test for detecting antibody to HIV that produces very quick results, usually in 5 to 30 minutes. For diagnosis of HIV infection, a positive rapid test is confirmed with a second rapid test made by a different manufacturer.

Reagent

A substance used in a chemical reaction to detect, analyze, or produce another substance.

Rebound

An increase in viral load following a previous decrease due to anti-HIV therapy.

Receptor

A molecule on the surface of a cell that serves as a recognition or binding site for antigens, antibodies, or other cellular or immunological components.

Referral

A suggestion that a patient see another individual (usually a specialist) for another opinion.

Refractory

Referring to a disease that does not readily respond to treatment.

Reinfection/Superinfection

The infection of an already HIV-infected person with another strain of HIV. The superinfection can be with a more aggressive strain of HIV.

Remission

The lessening in the severity of symptoms or duration of an outbreak of a disease.

Replication

The process of duplicating or reproducing.

Resistance

Reduction in a microorganism's sensitivity to a particular drug. Resistance is thought to result usually from a genetic mutation. In HIV, such mutations can change the structure of viral enzymes and proteins so that an antiviral drug can no longer bind with them as well as it used to.

Resistance Testing

The evaluation of bacteria or viruses such as HIV to determine whether they are resistant to the effects of drugs used for treatment. Resistance testing is an important tool to determine whether a patient with HIV infection is getting sicker because ARV drugs are no longer working.

See Genotype; Phenotype.

Retina

Light-sensitive tissue at the back of the eye that transmits visual impulses to the brain via the optic nerve.

See Retinitis.

Retinal detachment

Condition in which a portion of the retina becomes separated from the inner wall of the eye. In AIDS patients, it can result from retinal disease such as cytomegalovirus (CMV) retinitis.

Retinitis

Inflammation of the retina, linked in AIDS to cytomegalovirus (CMV) infection. Untreated, it can lead to blindness.

Retrovirus

A type of virus that, when not infecting a cell, stores its genetic information on a single-stranded RNA molecule instead of the more usual double-stranded DNA. HIV is an example of a retrovirus.

Reverse transcriptase

An enzyme capable of copying RNA into DNA during the HIV multiplication cycle. Several anti-HIV drugs — such as AZT, ddI, and ddC — are chemicals that act against the reverse transcriptase enzyme.

Reverse transcriptase inhibitor (RTI)

See Nucleoside reverse transcriptase inhibitor (NRTI).

Reverse transcriptase polymerase chain reaction (RT-PCR)

An FDA-approved test to measure viral load. The test is also known as PCR (polymerase chain reaction).

See Polymerase chain reaction (PCR).

Ribonucleic Acid (RNA)

A nucleic acid, found mostly in the cytoplasm of cells (rather than in the nucleus) that is important in the synthesis of proteins.

Risk Assessment

Risk assessment is a fundamental part of an HIV prevention counseling session in which the individual is encouraged to identify, acknowledge, and discuss in detail his or her personal risk for acquiring or transmitting HIV.

RNA

See Ribonucleic acid (RNA).

RT-PCR

See Reverse transcriptase polymerase chain reaction (RT-PCR).