Habit Training: behavioral technique that calls for scheduled toileting at regular interval on a planned basis to prevent incontinence.
Half-life: the time in which half the atoms of a radioactive species disintegrate.
Haploid: the chromosome number of a normal gamete (sperm or ovum). In humans, the haploid number is 23, representing one member of each chromosome pair. A single set of chromosomes (half the full set of genetic material) present in the egg and sperm cells of animals and in the egg and pollen cells of plants. Human beings have 23 chromosomes in their reproductive cells. See also -- diploid.
Haplotype: a way of denoting the collective genotype of a number of closely linked loci on a chromosome.
Hapten: a substance that combines specifically with antibody but does not initiate the formation of antibody unless attached to a high-molecular-weight carrier.
Health: a state of complete physical, social and mental well-being, and not merely the absence of disease or infirmity. Health is a resource for everyday life, not the object of living. It is a positive concept emphasizing social and personal resources as well as physical capabilities.
Health Benefit: in health economics, a health benefit is one which is recognized as providing a gain in terms of reduced costs or increased health.
Health Care: any type of services provided by professionals or paraprofessionals with an impact on health status.
Health Care Delivery: one of the functions of the health system, which deals with the medical and therapeutic measures, intended to preserve or improve the health condition of a patient.
Health Care Institution: an institution where delivery care is provided by health workers with midwifery skills (health centre, maternity unit, hospital).
Health Center: a facility that provides (ambulatory) medical and sanitary services to a specific group in a population.
Health Care Providers: individuals who are trained to provide various health services.
Health Economics: The study of how scarce resources are allocated among alternative uses for the care of sickness and the promotion, maintenance and improvement of health, including the study of how health care and health-related services, their costs and benefits, and health itself are distributed among individuals and groups in society.
Health Education: the planned and managed process of investing in education to achieve improvement in health of a population.
Health Expectancy: a population based measure of the proportion of expected life span estimated to be healthful and fulfilling, or free of illness, disease and disability according to social norms and perceptions and professional standards.
Health For All Policy: the attainment by all people of the world of a level of health that will permit them to lead a socially and economically productive life.
Health Gain: an increase in the measured health of an individual or population, including length and quality of life. Improvement in health status.
Health Indicator: an indicator applicable to a health or health-related situation. A health indicator is a characteristic of an individual, population, or environment which is subject to measurement (directly or indirectly) and can be used to describe one or more aspects of the health of an individual or population (quality, quantity and time).
Health Inequality and Inequity: health inequalities can be defined as differences in health status or in the distribution of health determinants between different population groups. For example, differences in mobility between elderly people and younger populations or differences in mortality rates between people from different social classes. It is important to distinguish between inequality in health and inequity. Some health inequalities are attributable to biological variations or free choice and others are attributable to the external environment and conditions mainly outside the control of the individuals concerned. In the first case it may be impossible or ethically or ideologically unacceptable to change the health determinants and so the health inequalities are unavoidable. In the second, the uneven distribution may be unnecessary and avoidable as well as unjust and unfair, so that the resulting health inequalities also lead to inequity in health.
Health Insurance: a mechanism by which money is raised to pay for health services by financial contributions to a fund; the fund then purchases health services from providers for the benefit of those for whom contributions are made or who are otherwise covered by the scheme.
Health Maintenance Organization (HMO): US health care sector term, an organization that contracts to provide comprehensive medical services (not patient reimbursement) for a specified fee each month.
Health Outcome: changes in health status (mortality and morbidity) which result from the provision of health (or other) services.
Health Plan: a broad term for all kinds of public or private schemes of health care coverage, including, for example, national health systems, sickness fund schemes, and private health insurance schemes.
Health Policy: a formal statement or procedure within institutions (notably government) which defines priorities and the parameters for action in response to health needs, available resources and other political pressures.
Health Promotion: the planned and managed process of encouraging and assisting improvement in the health of a population as distinct from the provision of health care services.
Health Resources: the means available for the operation of health systems, including human resources, facilities, equipment and supplies, financial funds and knowledge.
Health Sector: part of the economy dealing with health-related issues in society.
Health Services: any service which can contribute to improved health or the diagnosis, treatment and rehabilitation of sick people and not necessarily limited to medical or health-care services.
Health Services Research: a field on inquiry that examines the impact of the organization, financing and management of health care services on the delivery, quality, cost, access to and outcomes of such services.
Health Status: term for the state of health of an individual, group or population measured against defined standards/indicators.
Health System: the people, institutions and resources, arranged together in accordance with established policies, to improve the health of the population they serve, while responding to people's legitimate expectations and protecting them against the cost of ill-health through a variety of activities whose primary intent is to improve health. Set of elements and their relations in a complex whole, designed to serve the health needs of the population. Health systems fulfill three main functions: health care delivery, fair treatment to all, and meeting non health expectations of the population. These functions are performed in the pursuit of three goals: health, responsiveness and fair financing.
Health System Goal: a general objective towards which the health system should strive. The World Health Report 2000 identifies three intrinsic goals of any health system: health, which is also the defining goal responsiveness fair financing.
Health Target: health targets state, for a given population, the amount of change (using a health indicator) which could be reasonably expected within a defined period of time.
Health Technology: the application of scientific knowledge to solving health problems.
Health Technology Assessment: comprehensive evaluation and assessment of existing and emerging medical technologies including pharmaceuticals, procedures, services, devices and equipment in regard to their medical, economic, social and ethical effects.
Health Workforce: medical and paramedical services delivered to patients at home.
Healthy Public Policy: healthy public policy is a key component of the Ottawa Charter for Health Promotion (1986). The concept includes policies designed specifically to promote health (for example banning cigarette advertising) and policies not dealing directly with health but acknowledged to have a health impact (for example transport, education, economics) (Lock, 2000).
Helper Factor: sensitized T lymphocyte subpopulations release a helper factor that enables immunocompetent B cells to respond to antigens that they otherwise are unable to recognize. The stimulated B lymphocytes differentiate into plasma cells that produce antibody. The helper factor can also stimulate the B lymphocyte to produce a variant of the B cell, termed a killer cell (K cell) that is able to attack tumor cells only after the tumor cells have been exposed to specific antibody. Complement is not required for this action. See also killer cell.
Hemagglutinin: an antibody that reacts with a surface antigen determinant on red cells to cause agglutination of those red cells.
Hematuria: blood in urine, which may only be detected using a microscope.
Hemizygous: having only one copy of a particular gene. For example, in humans, males are hemizygous for genes found on the Y chromosome.
Hemolysin (Amboceptor): an anti-red cell antibody that can specifically activate complement (C') to cause lysis of red cells.
HER--2: see c-erb-b2 proto-oncogene.
Hereditary Cancer: cancer that occurs due to the inheritance of an altered gene within a family. See also -- sporadic cancer.
Hereditary Unstable DNA (Triplet Repeat Expansion): gene containing a region of triplet codon repeats such as (CGC)n. The number of triplet repeats can increase during meiosis. If the expansion of repeats reaches a critical number, the gene becomes methylated and is turned off, resulting in phenotypic abnormalities.
Hetero- : other or different; often used to mean "of a different species".
Heterochromatin: chromatin that remains condensed throughout interphase. It contains DNA that is genetically inactive and replicates late in the S phase of the cell cycle. There are two types of heterochromatin: constitutive and facultative.
Heterogeneous: a term that refers to the amount or degree of difference in a group (e.g., of research subjects).
Heteronuclear RNA: a form of RNA, a pre-mRNA, that exists before splicing and consists of both introns and exons.
Heterophil: pertains to antigenic specificity shared between species.
Heterophil Antigens: antigens common to more than one species.
Heterozygosity: the presence of different alleles at one or more loci on homologous chromosomes. The presence in a chromosome of dissimilar genes. Two different forms of the same gene in a cell. An oncogene is generally heterozygous. For example, one allele may be mutated while the other copy remains normal. In addition, different forms of a gene may be normal variants. Variations in the exact base sequence within DNA are common in the genome among humans. These are called polymorphisms and are often responsible for the heterozygous state.
Heterozygote: see -- heterozygosity.
Highest 20%/Lowest 20% income ratio: the quotient of the richest total income quintile divided by the poorest total income quintile in a given population, for a given country, territory, or geographic area, at a specific period in time, usually a year. Technical Note: Data are estimates based the percentage share of income or consumption.
Highly Conserved Sequence: DNA sequence that is very similar across several different types of organisms. see also -- gene, mutation.
High-throughput Sequencing: a fast method of determining the order of bases in DNA. See also -- sequencing.
Histocompatibility Antigens (Transplantation or HLA Antigens): antigens coded for by histocompatibility genes that determine the specific compatibility of grafted tissues and organs.
HIV: human immunodeficiency virus; the virus that causes AIDS.
HIV Voluntary Counseling and Testing (VCT): counseling prior to HIV test, testing itself, and post-test counseling conducted when results of the test are given to the patient.
HLA Antigens (Human Leukocyte Antigens): a genetic locus containing two closely linked groups of several alleles (a sublocus). They are present on the cell membranes of all nucleated cells and play a major role in determining graft take and rejection.
Homeobox: a short stretch of nucleotides whose base sequence is virtually identical in all the genes that contain it. Homeoboxes have been found in many organisms from fruit flies to human beings. In the fruit fly, a homeobox appears to determine when particular groups of genes are expressed during development.
Homogeneous: a term that refers to the amount or degree of similarity in a group (e.g., of research subjects).
Homolog: a member of a chromosome pair in diploid organisms or a gene that has the same origin and functions in two or more species.
Homologous: see allogeneic.
Homologous Chromosome: chromosome containing the same linear gene sequences as another, each derived from one parent.
Homologous Disease: see allogeneic disease.
Homologous Recombination: swapping of DNA fragments between paired chromosomes.
Homology: similarity in DNA or protein sequences between individuals of the same species or among different species.
Homozygote: an organism that has two identical alleles of a gene. See also -- heterozygote.
Homozygous: see -- homozygote.
HoNOS: Health of the Nation Outcome Scales.
Horizontal Transmission of Viruses: transmission of viruses between individual hosts of the same generation. See also vertical transmission of viruses.
Hospital: residential establishment equipped with inpatient facilities for 24-hour medical and nursing care, diagnosis, treatment and rehabilitation of the sick and injured, usually for both medical and surgical conditions, and staffed with at least one physician. The hospital may also provide outpatient services.
Hospital Bed: a regularly maintained and staffed bed for the accommodation and full-time care of a succession of inpatients, situated in wards or areas of the hospital where continuous medical care is provided. It is a measure of hospital capacity.
Hospital Beds Ratio: the number of hospital beds available per every 1,000 inhabitants in a population, at a given year, for a given country, territory, or geographic area.
Hospital Discharges Ratio: the number of hospital discharges per every 1,000 inhabitants in a population, at a given year, for a given country, territory, or geographic area. It represents an estimate of the degree of utilization of in-patient health care services. Hospital discharge is defined as the formal release of a hospitalized individual due to conclusion of the hospitalization stay, either by death, return home, or transfer to another institution. A hospital is defined as any medical facility with an organized medical and professional staff and beds available for continuous hospitalization of patients formally admitted to it for medical observation, care, diagnosis, or surgical and non-surgical treatment.
Host: the organism whose body serves to sustain a graft; interchangeable with the recipient.
Human Artificial Chromosome (HAC): a vector used to hold large DNA fragments. See also -- chromosome, DNA.
Human Capital: human skills and capabilities generated by investments in education and health.
Human Gene Therapy: See -- gene therapy.
Human Genome Initiative: collective name for several projects begun in 1986 by DOE to create an ordered set of DNA segments from known chromosomal locations, develop new computational methods for analyzing genetic map and DNA sequence data, and develop new techniques and instruments for detecting and analyzing DNA. This DOE initiative is now known as the Human Genome Program. The joint national effort, led by DOE and NIH, is known as the Human Genome Project.
Human Genome Project (HGP): formerly titled Human Genome Initiative. See also -- Human Genome Initiative.
Human Resources: people who work in the various professions of health care.
Humoral Antibodies: antibodies present in body fluids.
Humoral Immunity: pertains to the body fluids in contrast to cellular elements. It is initiated by the thymus-independent B cells. These B lymphocytes proliferate and differentiate into plasma cells that secrete immunoglobulins (IgG, IgM, IgA, IgD, and IgE).
Hybrid: the offspring of genetically different parents. See also -- heterozygote.
Hybridization (Dot Blot): a semiquantitative technique for evaluating the relative abundance of nucleic acid sequences in a mixture or the extent of similarity between homologous sequences. The process of joining two complementary strands of DNA or one each of DNA and RNA to form a double-stranded molecule.
Hybridoma: a hybrid cell that results from the fusion of an antibody-creating cell with a malignant cell; the progeny secrete antibody without stimulation and proliferate continuously in vivo and in vitro.
Hydronephrosis: dilation of the renal pelvis and calices and sometimes the collecting ducts. Hydronephrosis is secondary to obstruction of urine flow by calculi, tumors, neurologic disorders, or any various congenital anomalies.
Hydrophilic-Coated Catheter: one-time use tube devices that are coated with a substance that absorbs water and binds it to the device's surface.
Hypoxemia: decreased oxygen content in blood.
Hypoxia: decreased level of oxygen in tissue.
Hypoxic-Ischemic Encephalopathy: also called post-asphyxial encephalopathy, hypoxic-ischemic encephalopathy is a subtype of neonatal encephalopathy for which the etiology is considered to be limitation of oxygen and blood flow near the time of birth. Historically, it has been assumed that most cases of neonatal encephalopathy were hypoxic-ischemic encephalopathy, but epidemiologic studies have established that assumption is incorrect.
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