The following is a glossary of frequent terms relating to HIV/AIDS and HIV/AIDS clinical trials. A complete glossary can be found at

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Acquired Immunodeficiency Syndrome (AIDS) A disease of the body’s immune system caused by the human immunodeficiency virus (HIV).  AIDS is characterized by the death of CD4 cells (an important part of the body’s immune system), which leaves the body vulnerable to life-threatening conditions such as infections and cancers.
Antibody Also known as immunoglobulin.   A protein produced by the body’s immune system that recognizes and fights infectious organisms and other foreign substances that enter the body.  Each antibody is specific to a particular piece of an infectious organism or other foreign substance.
Antigen Any substance that can stimulate the body to produce antibodies against it.  Antigens include bacteria, viruses, pollen, and other foreign materials.
Antiretroviral (ARV) A medication that interferes with the ability of a retrovirus (such as HIV) to make more copies of itself.
Antiretroviral Therapy (ART) Treatment with drugs that inhibit the ability of retroviruses (such as HIV) to multiply in the body.   The antiretroviral therapy recommended for HIV infection is referred to as highly active antiretroviral therapy (HAART), which uses a combination of medications to attack HIV at different points in its life cycle.
Aspartate Amino Transferase (AST) and Alanine Amino Transferase (ALT) liver enzymes that are routinely measured as part of liver function tests.
Biopsy The surgical removal and examination of an organ or tissue to aid in diagnosis and treatment of a health condition.
Bone Marrow Aspirate The surgical removal and examination of an organ or tissue to aid in diagnosis and treatment of a health condition.
CD4 cells Also known as helper T cell or CD4 lymphocyte.  A type of infection-fighting white blood cell that carries the CD4 receptor on its surface.  CD4 cells coordinate the immune response, signaling other cells in the immune system to perform their special functions.  The number of CD4 cells in a sample of blood is an indicator of the health of the immune system.  HIV infects and kills CD4 cells, leading to a weakened immune system.
Cognitive impairment Loss of the ability to process, learn, and remember information.  The progression of HIV disease may lead to cognitive impairment.
Colonoscopy An outpatient procedure in which the rectum and the inside of the intestine are examined.  During a colonoscopy, a physician uses a colonoscope (a long, flexible instrument about 1/2 inch in diameter) to view the lining of the colon.  The colonoscope is inserted through the rectum and advanced to the large intestine.  A small amount of tissue will be removed for analysis, this is called a biopsy.
Drug Resistance The ability of some micro-organisms, such as bacteria, viruses, and parasites, to adapt so that they can multiply even in the presence of drugs that would normally kill them.
Enzyme Immunoassay (EIA)/Enzyme-Linked Immunosorbent Assay (Elisa) A highly sensitive laboratory test used to determine the presence of antibodies to HIV in the blood or saliva.   Positive ELISA test results indicate that a person is HIV infected, but these results should be confirmed with a highly specific laboratory test called a Western blot.
Genotypic Assay (GART) Also known as Genotypic Antiretroviral Resistance Test (GART) A test that determines if HIV is resistant to particular anti-HIV drugs.  The test analyzes a sample of the virus from an individual’s blood to identify any genetic mutations that are associated with resistance to specific drugs.
Genotypic resistance Genotypic resistance testing helps doctors make better treatment decisions for their patients when existing anti-viral therapies are not working effectively.  If drug resistance is found, a new treatment regimen may be chosen.  Genotypic resistance testing is ordered when viral load values (a measure of how much HIV is in your body) rise steadily during therapy, indicating treatment failure and the possibility of resistance.  The test may also be ordered before the start of therapy for an acute infection if a drug resistant virus is suspected, so that immediate, appropriate therapy is possible.  The test result identifies the viral mutations.  This is important information for physicians to help them predict which treatment regimen will work best for each patient.
Informed Consent Document A person’s agreement to participate in a clinical trial after understanding all aspects of the trial, including potential risks and benefits.
Institutional Review Board (IRB) A committee of experts who review and monitor clinical trials to ensure that they are ethical and that the rights of study participants are protected.  Federal regulations dictate that any institution that conducts or supports clinical trials must have an IRB.
Leukapheresis The removal of white blood cells (leukocytes) from the peripheral blood.   The process requires access to veins in both arms.  Blood is extracted from one arm into a machine that sorts out the various blood components according to their density and weight.  White cells are removed, and the rest of the blood is returned via a needle in the other arm.   The procedure usually takes 3-4 hours.
Opportunistic Infections (OIs) Illnesses caused by various organisms that occur in people with weakened immune systems, including people with HIV/AIDS.  OIs common in people with AIDS include Pneumocystis carinii pneumonia; cryptosporidiosis; histoplasmosis; toxoplasmosis; other parasitic, viral, and fungal infections; and some types of cancers.
Placebo Sometimes called a ‘sugar pill’.  A pill or other treatment that looks like the treatment being tested in a clinical trial but does not actually contain the active ingredient.  Placebos are used in some clinical trials to control for what is called the “placebo effect”: an effect that is caused by the power of suggestion alone.  The effects of the placebo are then compared to the effects of the active ingredient to determine if the ingredient is truly effective.
Pneumocystis Carinii Pneumonia / Pneumocystis Jiroveci Pneumonia (PCP) A lung infection caused by Pneumocystis jiroveci, a fungus related to Pneumocystis carinii (the species for which PCP was originally named).  PCP occurs in people with weakened immune systems, including people with HIV.  It is considered an AIDS-defining condition in HIV-infected individuals.  The first signs of infection are difficulty breathing, high fever, and dry cough.
Primary Care Provider A practitioner who sees people for common medical problems.  This person is usually a doctor, but may be a physician assistant or a nurse practitioner.
Protease Inhibitors (PI) A class of anti-HIV drug that prevents replication of HIV by disabling HIV protease.  Without HIV protease, the virus cannot make more copies of itself.
 Protocol  The detailed plan for conducting an experiment such as a clinical trial.  A clinical trial protocol is a lengthy document describing the trial’s rationale, purpose, information about the drug or vaccine under study, participant inclusion/exclusion criteria, study endpoints, and details of the trial design.
 Randomization  When participants of a clinical trial are assigned by chance to one of two or more treatment or placebo groups.  A randomized trial design helps researchers gather meaningful information and make valid statistical calculations.
 Retrovirus  A type of virus that stores its genetic information in a single-stranded RNA molecule, then constructs a double-stranded DNA version of its genes using a special enzyme called reverse transcriptase.  The DNA copy is then integrated into the host cell’s own genetic material.  HIV is an example of a retrovirus.
 Toxicity  Ability to poison or otherwise harm the body.
 Undetectable The point at which levels of HIV RNA in the blood are too low to be detected with a viral load test.  This does NOT mean that the virus has stopped replicating or has been removed from the body entirely, only that the small amount of virus remaining is below the test’s ability to measure it.   The viral load below which a test cannot detect the virus depends on the brand of the viral load test.
 Viral Load  The amount of HIV RNA in a blood sample, reported as number of HIV RNA copies per mL of blood plasma.  The VL provides information about the number of cells infected with HIV and is an important indicator of HIV progression and how well treatment is working.  The VL can be measured by different techniques, including branched chain DNA (bDNA) and reverse transcriptase-polymerase chain reaction (RT-PCR) assays.  VL tests are usually done when an individual is diagnosed with HIV infection and at regular intervals after diagnosis.
 Virologic Failure  Inability of anti-HIV drug treatment to reduce viral load or to maintain suppression of viral load.  Virologic failure is the most common type of treatment failure and may lead to immunologic and clinical failure.
 Western Blot  A laboratory technique used to detect a specific protein.   A Western blot test to detect HIV proteins in the blood is used to confirm a positive HIV antibody test (ELISA).