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"C"

Cachexia: A general weight loss and wasting occurring in the course of chronic disease.

Canadian AIDS Society (CAS): A coalition of community based AIDS organizations from across Canada.

Canadian Association for HIV Research (CAHR): An association of individuals (mostly University based) across Canada interested in fostering research in the area of HIV/AIDS.

Canadian Foundation for AIDS Research (CANFAR): A charitable foundation established to raise funds for AIDS research. A competition for funds is held yearly.

Canadian HIV Trials Network: A collaboration of HIV Clinics and programs funded under a research grant from the Canadian Institutes for Health Research (CIHR) to develop and undertake peer-reviewed research in HIV treatments.

Candida: A group of yeasts, in particular Candida albicans, that infect the mouth as well as other mucous membranes in the esophagus, intestines, vagina, throat and lungs. Oral or recurrent vaginal candidiasis is an early sign of immune system deterioration.

Candidiasis (Bronchi, Trachea or Lungs): An opportunistic disease caused by the yeast Candida albicans. Diagnosis is definitive after gross inspection by endoscopy, autopsy, or microscopy (histology or cytology) on a specimen obtained directly from the tissues affected (including scrapings from the mucosal surface), not from a culture.

Candidiasis (Esophageal): An opportunistic disease caused by the yeast Candida albicans. Definitively diagnosed by endoscopy, autopsy, or microscopy (histology or cytology) on a specimen obtained directly from the tissues affected (not from culture). Presumptively diagnosed by the recent onset of retrosternal pain on swallowing AND oral candidiasis diagnosed by the gross appearance of white plaques on an erythematous base or by the microscopic appearance of fungal mycelial filaments in an uncultured specimen scraped from the oral mucosa.

Case: A person who has a particular disease. A variety of criteria may be used to identify cases. Cases can include people who are included in surveillance databases and reports. Often, this term is used to refer to individuals seeking the advice of a health care provider.

Case Control Study: Refers to a type of study in which investigators compare a group of subjects with a particular disease (e.g., HIV infection or AIDS) and another group without the disease to determine which subjects were exposed to the factor of interest (e.g., injection drug use).

Catheter: A semi-permanent tube implanted usually in the chest or arm for long-term, metered administration of a drug into the veins. See also both Hickman Catheter and PICC Line.

CD4/CD8 Ratio: The ratio of CD4 to CD8 cells. A common measure of immune system status that is around two in healthy individuals.

CD4 Cell: The protein structure on the surface of a human cell that allows HIV to attach, enter, and thus infect a cell. CD4 receptors are present on CD4 cells (helper T-cells), macrophages and dendritic cells, among others. Normally, CD4 acts as an accessory molecule, forming part of larger structure (such as the T-cell receptor) through which T-cells and other cells signal each other.

CD4 Cell Count: The most commonly used surrogate marker for assessing the state of the immune system. As CD4 cell count declines, the risk of developing opportunistic infections increases. The normal range for CD4 cell counts is approximately 500-1500 cells/mmł of blood. CD4 count should be rechecked at least every six to 12 months if CD4s are greater than 500 cells/mmł. If the count is lower, testing every three months is advised. This may change with use of viral load to monitor disease progression.

CD8 Cell: One type of T-lymphocyte which bears the CD8 molecular marker on its surface. Some CD8 cells recognize and kill cancerous cells and those infected by intracellular pathogens (some bacteria, viruses and mycoplasma). These cells are called cytotoxic T-lymphocytes.

Cell-Mediated Immunity (CMI): One type of immune system response. Cell-mediated immunity provides protection against viruses, intracellular bacteria and malignant cells. In this type of immunity, the actions of T-lymphocytes and macrophages predominate.

Center for Disease Control and Prevention (CDC): The US federal public health agency serving as the center for preventing, tracking, controlling and investigating the epidemiology of AIDS and other diseases.

Central Nervous System (CNS): The brain, spinal cord and the meninges, (the protective membranes surrounding the brain and the spinal cord).

Centre for Infectious Diseases Prevention and Control (CIDPC): Canadian public health centre conducting national surveillance and research on the epidemiology and laboratory science related to HIV/AIDS and other sexually transmitted diseases (STDs).

Cerebrospinal Fluid (CSF): Fluid that bathes the brain and the spinal cord. A sample of this fluid is often removed from the body for diagnosis purposes by a lumbar puncture (spinal tap).

Certain: A clinical event, including an abnormal laboratory test result, which occurs in a plausible time in relationship to drug administration and cannot be explained by concurrent disease or other drugs or chemicals. The response to withdrawal of the drug (dechallenge) should be clinically plausible. The event must be pharmacologically or phenomenologically definitive, with the use of a satisfactory rechallenge procedure if needed.

Cervical Cancer: See Invasive Cervical Cancer.

Cervical Dysplasia: An abnormal tissue growth on the cervix which may progress to cancer if not treated in time. Cervical dysplasia is detected through a Pap smear. There are three classes of cervical dysplasia:

Mild dysplasia (CIN I): Only a few cells are abnormal. This stage is not cancerous.
Moderate dysplasia (CIN II): Abnormal cells involve about one-half of the thickness of the surface lining of the cervix. This stage is not cancerous.
Severe dysplasia or carcinoma-in-situ (CIN III): The entire thickness of cells is disordered, but the abnormal cells have not yet spread below the surface. Carcinoma-in-situ means "cancer in place". If this condition is not treated, it often will grow into an invasive cervical cancer.
In dysplasia and carcinoma-in-situ all of the abnormalities are confined to the surface lining (or "skin") of the cervix. In invasive cervical cancer, the cells are not only disordered throughout the entire thickness of the lining, but they invade the tissue underlying the surface.

Cervix: The lower, cylindrical terminus of the uterus that juts into the vagina and contains a narrow canal connecting the upper and lower parts of a women's reproductive tract.

Chancroid: Infectious venereal ulcer.

Chemokine Receptor Antagonists: A new class of antiretroviral drugs currently being studied in clinical trials.

Chemotherapy: The use of chemical agents (drugs) in the treatment of a disease. The term commonly, but not always, refers to cancer treatment.

Chronic: Refers to symptoms and diseases that last for an extended period of time without noticeable change.

Chronic Intestinal Cryptosporidiosis: More than one month in duration. Chronic infection caused by the parasite of bovine origin Cryptosporidium parvum that invades the intestinal tract. Symptoms can include watery diarrhea, stomach cramps, upset stomach, or fever. Definitively diagnosed by microscopy (histology or cytology).

Chronic Intestinal Isosporiasis: More than one month in duration. Isosporiasis is an intestinal disease caused by the parasite Isospora belli which is found in the tropics and subtropics. Symptoms include diarrhea, cramps, and weight loss. Diagnosed by microscopy (histology or cytology).

Clinical: Refers to physical signs and symptoms directly observable in the human body.

Clinical Trial: A study done to test an experimental drug in human beings to see if it is safe and effective.

CMV (Cytomegalovirus Disease): A virus belonging to the herpes family that causes serious illness in people with AIDS. Disease is most commonly seen in patients with CD4 count of <50 cells/mmł. CMV can develop in any part of the body but most often appears in the retina of the eye, the colon or the esophagus, and occassionally in the nervous system. CMV colitis, enteritis, esophagitis, gastritis, radiculomyelitis and pneumonitis are examples of possible end organ CMV disease that are considered AIDS-defining. Viral infection alone is not considered AIDS-defining. CMV can be diagnosed definitively by microscopy, culture or detection of antigen in a specimen obtained directly from the affected tissues or a fluid from those tissues.

CMV Encephalitis: Inflammation of the brain from CMV infection in an immunocompromised host.

CMV Polyradiculopathy: CMV infection of the peripheral nerves and spinal roots leading to generalized weakness and paralysis.

CMV Retinitis: CMV infection of the retina. The lesions it causes lead to deterioration in vision and ultimately blindness if untreated. See CMV.

Coccidioidomycosis: A disease caused by the spores of the fungus Coccidioides immitis native to SW United States and Mexico. Only disseminated (extrapulmonary) presentation is considered AIDS- defining. Diagnosis is definitive after microscopy (histology or cytology), culture or detection of antigen in a specimen obtained directly from the tissues affected or a fluid from those tissues.

Cohort: A cohort is a group of people followed over a specified period of time. It is most often applied to a group of people who are the subjects of a research study. In research, each member of a cohort has specific characteristics. These known characteristic can include:

Being free of the disease under investigation at the time the study begins;
Either having or not having specific risk behaviour patterns (risk factors);
Or having or not having prior experience of the treatment under investigation.

Cohort Study: The purpose of a cohort study is to investigate the development of new occurrence of a disease or to investigate how responses to treatment are related to specific factors. These factors can be recorded at the beginning of the study and/or during the course of the study. A cohort study begins with a group of people who will be participants in the study. This group of people is called a cohort. The cohort is followed for a specified time period, which can be weeks, months, years or decades. Follow-up data are collected at regularly defined periods either through the use of questionnaires, personal interviews, laboratory testing, medical examinations, or a combination of these methods. A cohort study is sometimes referred to as a prospective or a longitudinal study.

Co-Infection: Having two infections at the same time. For example, a person infected with both HIV and hepatitis C (HCV), or HIV and tuberculosis (TB), has a co-infection. With co-infection the progression of either disease can potentially be accelerated as a result of infection with the other disease.

Colposcopy: A procedure in which the surface of the uterine cervix is examined through a low-powered microscope for signs of cervical dysplasia or cancer. Colposcopy is a more accurate alternative to Pap smears, but requires considerably more skill to perform.

Compassionate Use: Refers to the process of providing experimental drugs usually prior to marketing to very sick patients who have no other treatment options available.

Complement: A complex series of blood proteins whose action complements the work of antibodies. Complement destroys bacteria, produces inflammation, and regulates immune reactions.

Complementary Medicine: Non-mainstream health care provided in addition or instead of standard medical practice.

Complete Blood Count (CBC): A screening of the most important cellular components of the blood. A CBC includes the total white blood count, counts of specific types of white blood cells, red blood cell count, hemoglobin level and platelet count.

Concealment: Refers to the activity of keeping something secret.

Condyloma Acuminatum: A projecting warty growth on the external genitals or the anus caused by infection with the human papillomavirus (HPV). It is usually a benign or non-cancerous growth. Condyloma acuminatum is also referred to as genital warts or verruca acuminata.

Confidence Interval (CI): Estimate of the spread between the lowest likely result (lower confidence limit) and the highest likely result (upper confidence limit). The true result of the study probably lies somewhere within this confidence interval.

Continuing Assessment: A self-explanatory term reinforcing the ongoing or long-term commitment to pharmacovigilance.

Control Arm: Refers to the group of participants in a clinical trial who receive standard treatment or a placebo, against which those receiving the experimental treatment are compared.

Control Event Rate: Often expressed as CER.

Corticosteroids: A type of medicine used to reduce inflammation. Corticosteroid drugs mimic a substance produced naturally by the adrenal glands.

CPCRA: Community Programs for Clinical Research on AIDS. A USA group that supports clinical trials based on local networks of practicing physicians.

Creatinine: The level of creatinine in the blood and urine provides a measure of kidney function.

Cross-Resistance: Refers to the phenomenon in which a microorganism that has acquired resistance to one drug through direct exposure has also developed resistance to one or more other drugs to which it has never been exposed. Cross-resistance arises because the mechanism of resistance to several drugs is the same and is due to identical genetic mutations.

Cross-Sectional Study: A cross-section is a random sample of a population, and a cross-sectional study examines this sample at one point in time. Successive cross-sectional studies can be used as a substitute for a longitudinal study.

Cryotherapy: The use of liquid nitrogen to freeze and destroy a lesion or growth, sometimes used to induce scar formation and healing to prevent further spread of a condition (for example, warts or molluscum contagiosum).

Cryptococcal Meningitis: An opportunistic infection caused by the yeast Cryptococcus neoformans and involving the membranes surrounding the brain and spinal cord. Symptoms may include severe headache, confusion, sensitivity to light, blurred vision, fever and speech difficulties. Left untreated, the disease can lead to coma and death. Standard treatments are amphotericin B (induction) and fluconazole (maintenance). Definitively diagnosed by microscopy (histology or cytology), culture, or detection of antigen in a specimen obtained directly from the tissues affected or fluids from those tissues.

Cryptococcosis (Extrapulmonary): Diagnosis is definitive after microscopy (histology or cytology), culture or detection of antigen in a specimen obtained directly from the tissues affected or a fluid from those tissues.

Cryptosporidiosis: An opportunistic infection caused by the intestinal parasite Cryptosporidium parvum, a very common parasite in animals. Transmission occurs through ingestion of food or water contaminated with animal feces. The parasite grows in the intestines and bile ducts and causes severe, chronic diarrhea, especially in people with AIDS. There are no standard treatments, but proposed treatments include paromomycin (humatin), azithromycin, letrazuril and various forms of concentrated cow and chicken antibodies.

CT Scan (Computed Tomography): A form of x-ray examination that utilizes a special beam to produce a detailed series of images of body sections. A CT scan is also referred to as a CAT scan.

Cytokine: One of the proteins produced by white blood cells that act as chemical messengers between cells. Cytokines can stimulate or inhibit the growth and activity of various immune cells in response to the particular type of disease present. Examples of cytokines are the various interleukins and tumor necrosis factor.

Cytomegalovirus: See CMV.

Cytomegalovirus Retinitis (With Loss of Vision): The most common CMV-related condition in people with HIV. Symptoms include loss of visual acuity and appearance of blind spots. Some forms of vision loss must be present to be considered AIDS-defining. It can be diagnosed definitively by microscopy, culture or detection of antigen in a specimen obtained directly from the affected tissues or a fluid from those tissues. It is most often diagnosed presumptively from a characteristic appearance on serial ophthalmoscopic examinations. Resolution of active disease leaves retinal scarring and atrophy with retinal pigment epithelial mottling.

Cytotoxic T-Lymphocyte: A type of CD8 or, less often, CD4 lymphocyte that kills diseased cells infected by a specific virus or other intracellular microbe. CTLs interact with MHC class I receptors on infected cells and have the prime role in cell-mediated immunity.

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