Glossary of terms

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• p24
• An HIV protein that makes up the virus core that surrounds HIV's genetic material. See also: Core.
• Package Insert
• Also known as prescribing information or product label. A document prepared by the manufacturer of a drug and approved by the Food and Drug Administration (FDA) to describe approved uses, dosages, contraindications, and potential side effects of the drug. This information is inserted inside each manufactured drug bottle and attached to any promotional or labeling materials.
• PACTG
• See: Pediatric AIDS Clinical Trials Group.
• Palliative Care
• Medical care that helps to alleviate symptoms of chronic illnesses without offering a cure. Palliative care offers therapies to comfort and support patients with terminal illnesses.
• Pancreas
• A gland located near the stomach that secretes digestive fluids that help to break down fats, proteins, and carbohydrates. The pancreas also secretes the hormones insulin and glucagon, which help to stabilize blood sugar.
• Pancreatitis
• Inflammation of the pancreas that can cause severe pain. Laboratory tests that indicate pancreatitis include increased blood levels of triglycerides and the pancreatic enzyme amylase. See also: Pancreas.
• Pancytopenia
• A lower than normal number of all types of blood cells, including red and white blood cells and platelets.
• Pandemic
• An outbreak of an infectious disease, such as HIV, that affects people or animals over an extensive geographical area. Also known as a global epidemic. See also: Epidemic.
• Pap Smear
• A method for the early detection of cancer and other abnormalities of the female genital tract. A Pap smear is done by placing a speculum in the vagina, locating the cervix, and then scraping a thin layer of cells from the cervix. The cells are placed on a slide, sent to a laboratory, and analyzed for abnormalities. HIV-infected women often have abnormal results of Pap smear tests, usually as a result of human papillomavirus (HPV) infection. See also: Human Papillomavirus, Cervical Cancer.
• Papilloma
• A tumor that grows on the skin, such as a wart or polyp. Human papillomavirus (HPV) is the virus that causes papillomas, including genital warts. See also: Human Papillomavirus, Genital Warts.
• Parasite
• An organism that lives and feeds on or within another living organism and causes some degree of harm. Immunocompromised people, such as those infected with HIV, are more likely to develop parasitic infections such as Pneumocystis jiroveci pneumonia (PCP) and toxoplasmosis.
• Parenteral

• 
  Any route into the body other than through the digestive system. For example, through the veins (intravenous), into the muscles (intramuscular), or through the skin (subcutaneous).

• Paresthesia
• Abnormal sensations such as burning, tingling, or a "pins-and-needles" feeling that occur without external stimulation. Paresthesia can occur as a symptom of peripheral neuropathy or as a side effect of certain anti-HIV drugs. See also: Peripheral Neuropathy.
• Passive Immunity
• The body's ability to prevent or fight a specific infection after receiving antibodies from another person. The most common example of passive immunity is when an infant receives the mother's antibodies by consuming her breast milk. See also: Antibody.
• Passive Immunotherapy
• The transfer of antibodies from one person to another to help the recipient fight infection. An example of passive immunotherapy is the use of plasma donated by healthy HIV-infected people who have high CD4 counts and high levels of anti-HIV antibodies. The plasma is administered to people with AIDS who have lost CD4 cells and can no longer make their own antibodies. Passive immunotherapy has been used with limited success in treating advanced HIV disease in adults, but it is still sometimes used in HIV-infected children. See also: Passive Immunity.
• Pathogen
• General term for any disease-causing organism.
• Pathogenesis
• General term for the origin and development of disease.
• PCP
• See: Pneumocystis Jiroveci Pneumonia.
• PCR
• See: Polymerase Chain Reaction.
• Pediatric AIDS Clinical Trials Group (PACTG)
• A large clinical trials network that evaluates treatments for HIV-infected children and adolescents and that develops new therapeutic approaches for preventing mother-to-child transmission (MTCT) of HIV.
• Pelvic Inflammatory Disease (PID)
• An infection of the upper female genital tract affecting the uterus, fallopian tubes, and ovaries. It is usually caused by the bacteria responsible for two common sexually transmitted diseases (STDs), gonorrhea and chlamydia. If left untreated, PID can cause severe pain, tubal pregnancy, and infertility. Severe cases may even spread to the liver and kidneys, causing dangerous internal bleeding and death.
• People Living With AIDS (PLWA)
• Infants, children, adolescents, and adults infected with HIV/AIDS.
• PEP
• See: Post-Exposure Prophylaxis.
• Peptide
• A short chain of amino acids that are chemically linked to one another. Longer chains of amino acids are referred to as polypeptides. See also: Polypeptide, Amino Acids.
• Perianal
• Around the anus.
• Perinatal
• The time period spanning shortly before and after birth.
• Perinatal Transmission
• The passage of HIV from an HIV-infected mother to her infant. The infant may become infected while in the womb, during labor and delivery, or through breastfeeding.
• Peripheral Blood Mononuclear Cell (PBMC)
• A general term for white blood cells containing one nucleus, particularly lymphocytes and macrophages. See also: Lymphocyte, Macrophage.
• Peripheral Neuropathy
• Condition characterized by sensory loss, pain, muscle weakness, and wasting of muscle in the hands, legs, or feet. It may start with burning or tingling sensations or numbness in the toes and fingers. In severe cases, paralysis may occur. Peripheral neuropathy may result from HIV infection itself or may be a side effect of certain anti-HIV drugs, particularly NRTIs. See also: Neuropathy.
• Persistent Generalized Lymphadenopathy (PGL)
• Chronic and persistent swollen lymph nodes in at least two areas of the body for at least three months. PGL occurs in people with persistent bacterial, viral, or fungal infections, and in individuals with weakened immune systems, including people with HIV.
• Pharmacokinetics
• The interaction of a drug with the body over a period of time. General pharmacokinetic processes are absorption, distribution, metabolism, and excretion. These processes are usually measured through blood and urine samples.
• PGL
• See: Persistent Generalized Lymphadenopathy
• Pharmacology
• The branch of medical science that studies the chemistry, effects, and uses of drugs. Pharmacology includes the study of a drug's therapeutic value, toxicology, and interaction with the body (pharmacokinetics). See also: Pharmacokinetics.
• Phase I Trials
• .
• Phase II Trials
• Early clinical studies that evaluate the safety and effectiveness of new drugs or other therapies. Phase II trials also help determine short-term side effects and risks associated with new drugs. This trial phase usually recruits no more than 100 people affected with the disease or condition under study.
• Phase III Trials
• Clinical studies that compare the effectiveness of new drugs to standard therapies for the disease or condition in question. This trial phase recruits a large population of people with the disease or condition under study, ranging from several hundred to several thousand volunteers. The results of these trials are used to evaluate the overall risks and benefits of the drug and provide the information needed for the Food and Drug Administration (FDA) to consider approving the drug.
• Phase IV Trials
• Clinical studies that occur after a drug has been approved by the Food and Drug Administration (FDA) to determine long-term safety and effectiveness. They are sometimes referred to as "post-marketing studies." This trial phase recruits the largest population of patients to gain additional information about the drug's risks, benefits, and optimal use.
• Phenotypic Assay
• A laboratory test that determines by direct experiment whether a particular strain of HIV is resistant to anti-HIV drugs. This is different from a genotypic assay, which uses an indirect method to find out if a particular strain of HIV has specific genetic mutations that are associated with drug resistance. See also: Resistance Testing, Genotypic Assay.
• Photosensitivity
• Increased sensitivity of skin to sunlight or ultraviolet light. Photosensitivity commonly causes reddening and blistering of the skin and in time increases a person's risk of skin cancer. Photosensitivity may occur as a side effect of some drugs or as a result of HIV infection.
• PHS
• See: Public Health Service.
• PID
• See: Pelvic Inflammatory Disease.
• Pill Burden
• The number and schedule of pills taken each day in a particular anti-HIV drug regimen. A high pill burden may lead to decreased treatment adherence because of the difficulty of taking a large number of pills properly. See also: Adherence.
• PIs
• See: Protease Inhibitors.
• 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. See also: Placebo Effect.
• Placebo Effect
• A positive or negative response to an inactive treatment (placebo) caused by a patient's or researcher's expectations that a particular treatment will have an effect. See also: Placebo, Placebo-Controlled Study.
• Placebo-Controlled Study
• A study that identifies the true effect of a treatment by comparing results in patients taking the actual treatment to those in patients taking an inactive look-alike, or placebo, treatment. See also: Placebo Effect.
• Plasma
• The clear, liquid part of the blood in which red blood cells, white blood cells, and platelets are suspended. Plasma contains nutrients, wastes, salts, gases, and proteins.
• Platelets
• A type of cell in the blood responsible for clotting. When blood vessels are damaged, platelets help to form a plug that prevents the loss of blood.
• PLWA
• See: People Living With AIDS.
• PML
• See: Progressive Multifocal Leukoencephalopathy.
• Pneumocystis Jiroveci
• A type of fungus that can cause severe pneumonia in humans, particularly in people with weakened immune systems and especially common in people with AIDS. P. jiroveci is related to P. carinii, the species for which PCP (pneumocystis carinii pneumonia) is named. See also: Pneumocystis Jiroveci 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. See also: Pneumocystis Jiroveci.
• Polymerase Chain Reaction (PCR)
• A laboratory technique that rapidly replicates tiny amounts of DNA so that it can be detected and measured. See also: Reverse Transcriptase-Polymerase Chain Reaction.
• Polyneuritis
• Inflammation of several nerves at the same time.
• Polypeptide
• A long chain of amino acids that are chemically linked to one another. Shorter chains of amino acids are referred to as peptides. See also: Amino Acids, Peptide.
• Polyvalent Vaccine
• A vaccine that combines multiple antigens. This type of vaccine may produce a stronger immune response or may provide protection from multiple strains of an infectious organism. See also: Antigen, Vaccine.
• Post-Exposure Prophylaxis (PEP)
• Administration of anti-HIV drugs within 72 hours of a high-risk exposure, including unprotected sex, needle sharing, or occupational needle stick injury, to help prevent development of HIV infection. See also: Prophylaxis.
• Postnatal
• The time period following birth (refers to the newborn). See also: Postpartum, Prenatal.
• Postpartum
• The time period after childbirth (refers to the mother). See also: Postnatal, Antepartum.
• Pre-Conception Counseling
• A specific type of health care recommended by the American College of Obstetrics and Gynecology for all women of childbearing age prior to pregnancy. Its purpose is to identify risks of pregnancy and childbirth for both mother and child, to provide education and counseling targeted to a woman's individual needs, and to treat or stabilize medical conditions prior to pregnancy in order to optimize the mother's and infant's health.
• Preclinical
• Refers to the preliminary testing of investigational drugs in laboratory animals that occurs before human testing may begin.
• Prenatal
• Period of time spanning conception to the begining of labor.
• Prescribing Information
• See: Package Insert.
• Prevalence
• The number of people in a population affected with a particular disease or condition at a given time. Prevalence can be thought of as a snapshot of all existing cases of a disease or condition at a specified time. See also: Incidence.
• Preventive HIV Vaccine
• A vaccine designed to prevent HIV infection in people who are HIV negative. Preventive HIV vaccines are not designed to treat those already infected with HIV. See also: Therapeutic HIV Vaccine
• Primary HIV Infection
• See: Acute HIV Infection.
• Primary Isolates
• Strains of HIV taken from an infected individual, as opposed to strains grown in the laboratory.
• Proctitis
• Inflammation of the lining of the rectum.
• Product Label
• See: Package Insert.
• Progressive Multifocal Leukoencephalopathy (PML)
• A rare brain and spinal cord disease caused by a virus and usually seen only in immunocompromised individuals, such as those with HIV. Symptoms vary, but include loss of muscle control, paralysis, blindness, speech problems, and an altered mental state. This disease often progresses rapidly and may be fatal. PML is considered an AIDS-defining condition in people with HIV.
• Prophylaxis
• Treatment to prevent the onset of a particular disease or to prevent recurrence of symptoms of an existing infection that has been brought under control.
• Protease
• An enzyme that breaks down long polypeptides into smaller protein units. HIV's protease enzyme cuts long chains of HIV polypeptide into the smaller, active proteins used in HIV replication. See also: Polypeptide.
• Protease Inhibitors (PIs)
• 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. See also: Protease.
• Protease-Sparing Regimen
• An anti-HIV drug regimen that does not include a PI. See also: Protease Inhibitors.
• Proteins
• Highly complex biological molecules consisting of specific combinations of amino acids linked together by chemical bonds. Proteins are required for the structure, function, and regulation of the body's cells, tissues, and organs, and each protein has unique functions. Examples of proteins are enzymes, cytokines, antibodies, and the major components of hair, skin, and muscle. See also: Peptide, Amino Acids, Polypeptide.
• 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. See also: Clinical Trial, Endpoint, Inclusion/Exclusion Criteria.
• Protozoa
• Large, diverse group of unicellular (one-celled) animals. Some protozoa cause diseases in people with weakened immune systems, including people with HIV or AIDS. Protozoa are responsible for some of the AIDS-defining opportunistic infections, notably toxoplasmosis and cryptosporidiosis.
• Provirus
• A DNA version of HIV's genetic material that has been integrated into the host cell's own DNA. See also: Integration.
• Pruritus
• An intense itching sensation that produces the urge to rub or scratch the skin for relief.
• PubMed
• Database and search engine that provides access to citations for more than 11 million biomedical articles dating back to the 1950s. The database is maintained by the National Library of Medicine (NLM). PubMed includes links to free full-text articles, where they are available, and also connects users with related resources. www.ncbi.nlm.nih.gov
• Public Health Service (PHS)
• An office within the U.S. Department of Health and Human Services (DHHS). The Public Health Service is composed of several agencies, including the Food and Drug Administration (FDA) and the National Institutes of Health (NIH), which oversee different aspects of health care in the United States. Guidelines for the management of various diseases, including HIV infection, are released through the PHS.
• Pulmonary
• Pertaining to the lungs.
• Purified Protein Derivative (PPD)
• A substance used in the tuburculin skin test to determine if a person has been exposed to Mycobacterium tuberculosis, the bacterium that causes tuberculosis (TB). PPD is usually injected just below the skin. A hard red bump or a swollen area at the injection site indicates that the person was exposed to the bacterium. Additional tests are required to determine if the person has active TB infection. See also: Tuberculin Skin Test, Tuberculosis.