Important note: Information in this article was accurate in January 2001. The state of the art may have changed since the publication date.ABSCESS: an isolated accumulation of pus associated with a localized infection. Abscesses may result in tissue destruction, pain, and swelling; severe abscesses may require surgical drainage.
ADHERENCE: following a prescribed treatment regimen, including correct dosage, number of doses per day, and dietary restrictions.
AMYLASE: an enzyme produced by the salivary glands and the pancreas that helps break down food. An abnormal increase in serum amylase levels may indicate
inflammation of the pancreas (pancreatitis).
ANAL INTRAEPITHELIAL NEOPLASIA (AIN): the abnormal growth of cells of the anus, which may be a precursor of anal cancer.
ANTIBODY (AB, IMMUNOGLOBULIN, IG):
an immunoglobulin protein secreted by activated plasma cells, which evolve from B-cells. Antibodies are present throughout the blood and tissues; they are produced in response to stimulation by foreign antigens as part of the body's defense against disease. Specific antibodies bind to and act upon specific antigens; the antigen/antibody reaction forms the basis of humoral (TH2) immunity. Neutralizing antibodies destroy or inactivate infectious agents, while enhancing antibodies promote infection.
ANTIRETROVIRAL: an agent (e.g., AZT, ddI, or nevirapine) that suppresses the activity or replication of retroviruses such as HIV.
BENZOIN: a dry, brittle resinous substance used medicinally in benzoic acid.
CANDIDIASIS: a disease caused by a Candida fungus, usually C. albicans (but also C. glabrata, C. tropicalis, or C. krusei). Candidiasis can affect the skin, nails and mucous membranes throughout the body including the mouth (thrush), esophagus, vagina (yeast infection), intestines and lungs. Oral and vaginal candidiasis may be early signs of immune impairment in HIV positive individuals
CD4 CELL (CD4 LYMPHOCYTE, T-HELPER CELL, T4 CELL): a type of white blood cell that carries the CD4 cell surface receptor and helps the body fight infection. CD4 cells release cytokines (chemical messengers) that coordinate a broad range of immune system activities including killer cell activation and antibody production.
CENTER FOR EPIDEMIOLOGICAL STUDIES-DEPRESSION SCALE (CES-D): a short self-report scale designed to measure depressive symptomatology in the general population. CES-D also measures the severity of the depression, and can be used to identify high-risk groups.
CERVIX (adjective CERVICAL): the cylindrical, lower part of the uterus leading into the vagina.
CHEMOTHERAPY: the use of chemicals or drugs to treat disease; the term is typically used to refer to cancer treatment.
CHLAMYDIA (CHLAMYDIASIS): an infection, usually sexually transmitted, with the bacteria Chlamydia trachomatis. Chlamydiasis is a common sexually transmitted disease in the U.S. It may be asymptomatic or include symptoms such as genital inflammation and discharge, pelvic pain, and fever. Untreated chlamydiasis may lead to pelvic inflammatory disease (PID) and infertility. Chlamydia may also cause eye disease (trachoma) and pneumonia.
CIDOFOVIR (VISTIDE): a nucleoside analog drug used to treat refractory cytomegalovirus (CMV) infection and acyclovir-resistant herpes simplex virus.
COHORT: a group of individuals in a study who share a demographic, clinical, or other statistical characteristic (e.g., age or study site).
COLON: the large intestine, extending from the cecum (where it meets the small intestine) to the rectum.
CORECEPTOR: a second cell surface receptor required for entry by a pathogen into a host cell, or for initiation of a biological process. HIV requires both the CD4 receptor and a coreceptor (e.g., CCR-5 or CXCR-4) to enter a cell.
CROHN'S DISEASE: a chronic type of enteritis, or inflammation of the intestines.
CYTOMEGALOVIRUS (CMV, HUMAN HERPESVIRUS 5): a herpesvirus. CMV infection often occurs in healthy individuals without causing symptoms. In immunocompromised individuals (usually with CD4 cell counts below 50 cells/mm3), CMV may cause serious illness including retinitis (inflammation of the retina), pneumonia, colitis (inflammation of the large bowel), and encephalitis. CMV infection of a pregnant woman may lead to congenital abnormalities in the newborn. CMV may be treated with ganciclovir, foscarnet, or cidofovir.
CYTOPLASM: the gel-like substance that composes cells and lies outside the cell nucleus. The cytoplasm contains numerous structures or organelles (e.g., mitochondria) and component substances.
DEMOGRAPHICS: the characteristics of a population (e.g., sex, race, age, or geographic location).
DNA (DEOXYRIBONUCLEIC ACID): a molecule that encodes genetic information and is found in the nucleus of cells as a twisted double-stranded chain. The particular sequence of four chemical building blocks (nucleotides)-adenine, cytosine, guanine, and thymine-that make up a DNA chain determines the unique genetic code of an individual.
DRUG RESISTANCE: the mutation of a microorganism in such a way that it loses its sensitivity to a drug; a resistant organism can function and replicate despite the drug's presence. Contrast with susceptible. Genotypic and phenotypic resistance tests are used to measure whether an organism is resistant to a drug.
ELECTROLYTE: an electrically charged element or compound (e.g., sodium, potassium) found in body fluids, tissues, and cells. An imbalance of electrolytes can result from prolonged vomiting or diarrhea, and may lead to the disruption of many bodily processes, possibly resulting in muscle weakness, cramps, or seizures.
EPIDEMIOLOGY: the study of the frequency, distribution, and behavior of a disease within a population.
EPITHELIUM: a thin layer of cells that covers the internal and external surfaces of the body, including body cavities, ducts, and vessels. The epithelium includes squamous epithelial cells and columnar epithelial cells, which meet and overlap at transition zones.
ETIOLOGY: the cause of a disease; the study of causes of disease.
GENE: the unit of heredity. A gene contains hereditary information encoded in the form of DNA, and is located at a specific position on a chromosome in a cell's nucleus. Genes determine many aspects of anatomy and physiology by controlling the production of proteins. Each individual has a unique sequence of genes, or genetic code.
GENITAL HERPES: see herpes simplex virus.
GENOTYPE (adjective GENOTYPIC): the specific genetic makeup or "blueprint" of an organism. Genotypic resistance testing determines whether an organism's genetic structure contains certain mutations that make it resistant to a drug. Contrast with phenotype.
GONORRHEA: a sexually transmitted disease caused by the bacteria Neisseria gonorrhoeae. Gonorrhea may be asymptomatic or may include symptoms such as urethritis, discharge, pelvic pain and inflammation of the tissues of the genitals, rectum, and/or throat. Untreated gonorrhea may spread to the upper genital tract and lead to pelvic inflammatory disease (PID) in women and may become disseminated, affecting other organs such as the heart and brain.
HAART: highly active antiretroviral therapy, a term for potent combination anti-HIV treatment that usually includes a protease inhibitor.
HEMOGLOBIN (Hb): the red, iron-based pigment in red blood cells that enables them to transport oxygen. Normal hemoglobin values are 12-15 grams per deciliter (100 milliliters) for women and 14-16 grams per deciliter for men.
HEPATITIS A (HAV, INFECTIOUS HEPATITIS): an inflammatory viral disease of the liver with a short incubation period. Hepatitis A virus (HAV) may be transmitted by eating contaminated food, by fecal-oral contact, and/or through household contact. Hepatitis A may be mild to severe; symptoms include fever, nausea, and jaundice. A two-dose anti-HAV vaccine is available.
HEPATITIS B (HBV, SERUM HEPATITIS): a viral liver disease that may be acute or chronic, and can be life-threatening. Symptoms include fever, malaise, fatigue, jaundice, abdominal tenderness, and elevated liver enzymes. Some individuals are chronic asymptomatic carriers; chronic hepatitis B may result in liver cirrhosis and/or cancer. The hepatitis B virus (HBV) can be transmitted by sexual contact, shared needles, or contaminated blood products. Interferon-alpha is used as a treatment; a three-dose anti-HBV vaccine is available.
HERPES SIMPLEX VIRUS (HSV-1, HSV-2, HUMAN HERPESVIRUS 1, 2): a herpesvirus that causes recurring lesions. Herpes simplex virus type 1 (HSV-1) usually produces blisters on the lips or in the mouth ("cold sores" or "fever blisters"). HSV type 2 (HSV-2) is usually sexually transmitted and generally produces lesions in the genital or anal area. Both HSV-1 and HSV-2 are treated with acyclovir; ganciclovir or foscarnet are used to treat acyclovir-resistant HSV.
HERPES ZOSTER (SHINGLES): a condition characterized by painful blisters that typically appear in a dermatomal (linear) distribution on the skin following a nerve pathway; blisters generally dry and scab leaving minor scarring. Shingles is caused by reactivation of a previous infection with the varicella-zoster virus (VZV) that initially causes chickenpox; VZV lies dormant in the nerves and reactivates when immune defenses are weakened. Shingles outbreaks may recur more frequently and VZV may become disseminated in people with HIV disease.
HETEROZYGOTE: a nucleus, cell, or organism with different alleles (gene variants) of one or more specific genes.
HETEROZYGOUS: possessing two different alleles, or gene variants, at a given site on a chromosome. Contrast with homozygous.
HOMOZYGOUS: possessing two copies of the same allele, or gene variant, at a given site on a chromosome. Contrast with heterozygous.
IMMUNOSUPPRESSION: reduced function of the immune system; a state in which the immune system defenses have been suppressed, damaged or weakened.
INCIDENCE (INCIDENCE RATE): the number of new cases of a disease or condition in a specific population during a given period of time. The incidence rate is determined by dividing the number of new cases by the total population. Contrast with prevalence.
IN SITU: occurring in place or at a specific site. Carcinoma in situ is a tumor that has not invaded surrounding tissues.
INTRAVENOUS (IV): injected directly into a vein.
KAPOSI'S SARCOMA (KS): an abnormal or cancerous proliferation of cells of the blood and/or lymph vessels causing tumors on the skin, mucous membranes, and/or internal organs. KS typically appears as purplish or brownish lesions, and is associated with a herpesvirus (KSHV, or HHV-8). It occurs more commonly among HIV positive gay and bisexual men than among others with HIV disease, indicating that it may be sexually transmitted.
LESION: any abnormal tissue change caused by disease or injury.
LOGISTIC REGRESSION: a variation of ordinary regression, useful when the observed outcome is restricted to two values, which usually represent the occurrence or nonoccurrence of some outcome event (usually coded as 1 or 0, respectively). It produces a formula that predicts the probability of the occurrence as a function of the independent variables.
LONGITUDINAL STUDY: refers to a study that follows participants over an extended period of time.
LYMPH NODE (LYMPH GLAND): a small, bean-sized organ located throughout the body, with concentrations in the neck, groin, and armpits. Lymph nodes filter out antigens and are the site of antigen presentation and immune cell activation. The lymph nodes are a reservoir site for HIV.
LYMPHOCYTE: a type of white blood cell (e.g., T-cell, B-cell, or natural killer cell) that plays a part in immune defense.
MALIGNANCY: a cancer, neoplasm, or tumor that grows in an uncontrolled manner, and may invade nearby tissue, or metastasize (spread) to other sites in the body.
MCV: see mean corpuscular volume.
MEAN: a statistical measurement of the central tendency, or average, of a set of values. Contrast with median.
MEAN CORPUSCULAR VOLUME (MCV): the average volume of erythrocytes, conventionally expressed in cubic micrometers per red blood cell.
MEDIAN: the number within a series that is preceded and followed by an equal number of values. Contrast with mean.
MEDICAL OUTCOMES STUDY SHORT-FORM 36 (SF-36): a 36-item instrument for measuring health status and outcomes from the patient's point of view. SF-36 was designed for use in surveys of general and specific populations, health policy evaluations, and clinical practice and research.
METHAMPHETAMINE (CRYSTAL, SPEED): a drug that exerts a stimulatory effect on the nervous system.
MICROBICIDE: an agent that inactivates, kills, or destroys microbes. Vaginal and anal microbicides are under study as a means of preventing HIV transmission.
MITOMYCIN C: an antibiotic that inhibits DNA synthesis by cross-linking the strands.
MULTIVARIATE ANALYSIS: a statistical analysis technique in which multiple variables are analyzed separately to determine the contribution made by each variable to an observed result. Compare with univariate analysis.
MYCOBACTERIUM AVIUM COMPLEX (MAC): an opportunistic disease caused by Mycobacterium avium or Mycobacterium intracellulare, bacteria found in soil and water. In immunosuppressed persons, the bacteria can infect the lymph nodes, intestines, bone marrow, liver, spleen, spinal fluid, lungs, and the gastrointestinal tract, and may become disseminated. MAC is the most common bacterial infection in persons with advanced AIDS (usually with CD4 cell counts below 50-75 cells/mm3). Symptoms include diarrhea, wasting, fever, night sweats, fatigue, and spleen enlargement. Clarithromycin is used as treatment and prophylaxis for MAC.
NEUTROPENIA: an abnormally low number of neutrophils in the circulating blood, leading to susceptibility to infection.
NON-HODGKIN'S LYMPHOMA (NHL): a type of cancer of the lymph nodes. NHL is characterized by abnormal growth of B-cells, and is the most common type of lymphoma in people with HIV/AIDS.
NUCLEUS: the central part of a cell that contains its genetic material.
OPPORTUNISTIC INFECTION (OI): a disease caused by a microorganism that does not normally cause illness in a person with a healthy immune system, but that may cause serious disease when the immune system is weakened. Common OIs in HIV positive people include Pneumocystis carinii pneumonia (PCP), Mycobacterium avium complex (MAC), and cytomegalovirus (CMV) infection.
PATHOLOGY: the study of disease, focusing on causes, development and progress of disease, and how the body is affected.
PERSON-YEAR: a value determined by multiplying the number of persons by the number of years. For example, one person followed for ten years equals ten person-years, and ten persons followed for one year also equals ten person-years.
PH: a logarithmic scale used to describe the acidity or alkalinity of a solution; a measure of the hydrogen concentration of a solution. Water has a neutral pH of 7. A pH below 7 is acidic; a pH above 7 is alkaline (or basic).
PHENOTYPE (adjective PHENOTYPIC): visible characteristics and/or behavior that result from the interaction of an organism's genetic "blueprint" (genotype) and the environment. Phenotypic resistance testing determines whether an organism is susceptible to a specific drug in a test tube. Contrast with genotype.
PLACEBO: an inert, inactive substance; a "sugar pill." Experimental therapies are compared with placebo in many clinical trials.
PNEUMOCYSTIS CARINII PNEUMONIA (PCP): a life-threatening opportunistic type of pneumonia believed to be caused by a protozoan. PCP is a common infection that can cause severe illness in immunocompromised people (especially those with CD4 cell counts of less than 200 cells/mm3); it remains a leading cause of death in people with AIDS. Symptoms include dry cough, fever, chest tightness, and shortness of breath. Pneumocystis carinii can also infect other parts of the body. First-line treatment and primary prophylaxis is TMP-SMX (Bactrim, Septra); other treatments and prophylaxes include dapsone, pentamidine, and atovaquone.
PODOPHYLLIN RESIN: an acidic resin from the May apple plant that is used to remove warts.
PREVALENCE (PREVALENCE RATE): the proportion of individuals with a condition in a specific population during a given time. The prevalence rate is determined by dividing the number of people with the condition by the total population. Contrast with incidence.
PROPHYLAXIS (PX): therapy that helps to prevent a disease or condition before it occurs (primary prophylaxis) or recurs (secondary prophylaxis).
RETINITIS: inflammation of the retina, potentially resulting in the loss of vision. Cytomegalovirus (CMV) infection is a common cause of retinitis in people with HIV disease.
SEQUELAE: conditions resulting from a disease or injury.
SEROCONVERSION: the development of antibodies directed against an antigen; the change in a person's antibody status from negative to positive. Vaccine-induced seroconversion is not an infection.
SERONEGATIVE: having a blood test that does not indicate infection with a microorganism (e.g., HIV), either by the presence of antibodies or antigen.
SEROPOSITIVE: having a blood test result that indicates infection with a microorganism (e.g., HIV). A test may detect either antibodies to an organism (antibody positive) or the organism or its proteins (antigen positive).
SEROSTATUS: the presence or absence of an organism in the blood. Serostatus may be measured by the presence of antibodies against an organism (antibody status) or by the presence of the organism itself (antigen status). If antibodies or organisms are present, a person is said to be seropositive; if not, the person is seronegative.
SHEDDING: release of infectious particles (e.g., bacteria or viruses) into the environment, for example by sneezing, by fecal excretion, or from an open lesion.
SUSCEPTIBLE: vulnerable to or potentially able to contract a disease. Also refers to a microorganism that is vulnerable to the effects of a drug. Contrast with drug resistance.
SYPHILIS: a sexually transmitted infectious disease caused by the spirochete bacterium Treponema pallidum. Stages of syphilis are primary (a nonpainful chancre in the mouth or anogenital area), secondary (a generalized rash, including the palms and soles, which occurs several weeks to a year later), a dormant stage in which the spirochetes remain in the body without causing symptoms, and tertiary (which may affect many organs including the brain, leading to dementia [neurosyphilis] and death). In immunocompromised persons, syphilis may progress more rapidly and be resistant to treatment. Penicillin is the usual treatment.
THROMBOCYTOPENIA: an abnormally low number of platelets; the condition may result in abnormal bleeding and bruising. The normal platelet range is 150,000-300,000 per millimeter of blood. Thrombocytopenia may be controlled by the administration of certain cytokines or by removal of the spleen.
TRICHLOROACETIC ACID (TCA): a strong acid solution used to dissolve warts.
TRIMETHOPRIM-SULFAMETHOXAZOLE (TMP-SMX, BACTRIM, SEPTRA): an antibiotic drug combination. TMP-SMX is the preferred first-line therapy for prophylaxis and treatment of PCP, and may be effective against other OIs such as toxoplasmosis. Side effects include fever, nausea, diarrhea, photosensitivity, skin rash, and neutropenia. Desensitization to the drug is often possible using slowly increasing dosages.
ULCER (ULCERATION): an open sore on the skin or mucous membrane characterized by sloughing of inflamed dead tissue.
UNIVARIATE ANALYSIS: a statistical analysis that considers only one factor or variable at a time. Compare with multivariate analysis.
VIROLOGICAL FAILURE: treatment breakthrough; an increase in viral load after it has been suppressed with antiretroviral drugs.
VULVA: the external female genitalia, including the clitoris and the inner and outer labia surrounding the urethral and vaginal openings.
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