Noninvasive prenatal diagnosis Health Dictionary

The process of determining health status and the factors responsible for producing it. It may be applied to an individual, family, group or community. The term is applied both to the process of determination and to its findings. See also “principal diagnosis”.... diagnosis

A list of the possible diagnoses that might explain a patient’s symptoms and signs, and from which the correct DIAGNOSIS will be extracted after further investigations.... differential diagnosis

A term used to describe any medical procedure that does not involve penetration of the skin or entry into the body through any of the natural openings.

Examples include CT scanning and echocardiography.

The term noninvasive is sometimes also applied to noncancerous tumours that do not spread throughout body tissues.... noninvasive

The use of information technology to assist health care professionals in diagnosis. This usually involves a dialogue between a computer system and a clinician. The systems are generally regarded as support systems for clinicians; the final responsibility for decision-making resides with the clinician.... computer-assisted diagnosis

A system used for payment under prospective payment systems. It classifies treatments by diagnosis, measuring the relative complexity of a hospital procedure and accounting for the resources used in the procedure. The system accounts for principal diagnosis, secondary diagnosis, surgical procedures, age, sex and presence of complications.... diagnosis-related group

1 Represents classes of hospital patients with similar clinical characteristics. DRGs form a clinical grouping system which describes hospital discharges according to medical condition. 2 A system used for payment under prospective payment systems. It classifies treatments by diagnosis, measuring the relative complexity of a hospital procedure and accounting for the resources used in the procedure. The system accounts for principal diagnosis, secondary diagnosis, surgical procedures, age, sex and presence of complications.... diagnosis-related group (drg)

Prenatal screening of fetal abnormalities may be the result of screening tests carried out on most or all pregnant women, or as the result of speci?c diagnostic tests performed to detect speci?c conditions. Prenatal diagnosis is important as it will identify babies who might need medical or surgical treatment before or soon after birth. In addition, it may also detect severe abnormalities for which parents might decide to have a therapeutic ABORTION.

ULTRASOUND scanning is probably the most widely used diagnostic tool in obstetric practice. It can detect structural abnormalities such as SPINA BIFIDA and CLEFT PALATE and even cardiac and renal problems. A series of scans can assess whether the baby is growing at a normal rate; ultrasound may also be used to assist with other diagnostic tests (e.g. AMNIOCENTESIS – see below).

Tests on the mother’s blood can also diagnose fetal abnormalities. Alphafetoprotein (AFP) is produced by babies and ‘leaks’ into the AMNIOTIC FLUID and is absorbed by the mother. In spina bi?da and other neural-tube defects there is increased leakage of AFP, and a blood test at 16 weeks’ gestation can detect a raised level which suggests the presence of these abnormalities.

The triple test, also performed at 16 weeks, measures AFP and two hormones – HUMAN CHORIONIC GONADOTROPHIN and unconjugated OESTRADIOL – and is used in diagnosing DOWN’S (DOWN) SYNDROME.

Amniocentesis involves inserting a needle through the mother’s abdominal wall into the uterus to remove a sample of amniotic ?uid at 16–18 weeks. Examination of the ?uid and the cells it contains is used in the diagnosis of Down’s syndrome and other inherited disorders. The test carries a small risk of miscarriage.

Chorionic villus sampling may be used to diagnose various inherited conditions. A small amount of tissue from the developing PLACENTA is removed for analysis: this test has the advantages of having a lower incidence of miscarriage than amniocentesis and is carried out at an earlier stage (9–13 weeks).

Analysis of a blood sample removed from the umbilical cord (cordocentesis) may diagnose infections in the uterus, blood disorders or inherited conditions.

Direct observation of the fetus via a viewing instrument called a fetoscope is also used diagnostically and will detect structural abnormalities.

Most tests have a recognised incidence of false positive and negative results and are therefore usually cross-checked with another test. Counselling of the parents about prenatal tests is important. This allows them to make an informed choice which may not necessarily involve terminating the pregnancy if an abnormality is found. (See PREGNANCY AND LABOUR.)... prenatal screening or diagnosis

The medical condition that is ultimately determined to have caused a person’s need for medical care. The principal diagnosis is used to assign every person to a diagnosis-related group. This diagnosis may differ from the admitting and major diagnoses. See also “diagnosis”.... principal diagnosis

The period of pregnancy before childbirth.... prenatal

see prenatal diagnosis.... antenatal diagnosis

the coexistence of a severe mental disorder with a *substance misuse disorder.... dual diagnosis

a technique for improving the sensitivity and specificity of bladder cancer diagnosis at cystoscopy using a light-sensitive agent. This agent is instilled into the bladder, taken up by the epithelial cells, and converted into a porphyrin that accumulates only in malignant and premalignant cells. It fluoresces under light of a specific wavelength and is thus highlighted against normal bladder mucosa.... photodynamic diagnosis

*screening tests carried out to estimate the risk of chromosomal or other abnormalities being present in a developing fetus. They include blood tests to measure levels of *human chorionic gonadotrophin (hCG), *PAPP-A, *alpha-fetoprotein (AFP), inhibin (see activin), and *unconjugated oestriol (uE3) (see also triple test) and also ultrasound scanning for the presence of soft markers (see ultrasound marker; nuchal translucency scanning). If the results indicate a high risk of abnormalities being present, a diagnosis may be confirmed by more invasive procedures (see prenatal diagnosis).... prenatal screening

The use of computer technology in diagnostic tests and procedures.

Probability-based computer systems store information on thousands of cases of different disorders detailing exact type, location, duration, symptoms, medical history, and diagnosis.

A patient’s symptoms and medical history can be entered into a computer, which then compares the details with existing data and produces a list of the most likely diagnoses.

Such technology is not currently in common use in hospitals, but is of value for people isolated from medical services, such as oil-rig crews.

Computers programmed to interpret visual data, such as abnormal cells, have potential use in certain types of blood test and cervical smear tests.

Computers are also used in investigative procedures such as CT scanning and MRI.... computer-aided diagnosis

(NIV) mechanical assistance with breathing that does not require the insertion of an endotracheal tube (see intubation). In noninvasive intermittent positive-pressure ventilation (NIPPV) air is blown into the lungs through a close-fitting mask: designs range from helmet-like devices to nasal cushions and full-face or nasal masks (see also Nippy). A ventilator then applies positive pressure to the mask in a cyclical fashion. The technique simplifies the process of ventilation in respiratory failure and reduces or eliminates the need for paralysis and anaesthesia, which are required for endotracheal intubation. See also BiPAP; continuous positive airways pressure.

Negative-pressure ventilation involves the use of devices that draw air into and out of the lungs noninvasively by applying negative pressure in a cyclical way (see ventilator).... noninvasive ventilation

(PGD) a diagnostic procedure carried out on embryos at the earliest stage of development, before implantation in the uterus. Access to these early embryos requires the *in vitro fertilization of egg cells: three days after fertilization one or two cells are aspirated from the six-cell embryo; alternatively, tissue is removed from an embryo at five or six days, when it has reached the *blastocyst stage. Isolated cells can then be genetically analysed, allowing the transfer of selected embryos to the mother. One of the major applications of PGD is for the detection (using the *FISH technique) of chromosomal abnormalities, especially *aneuploidies (e.g. Down’s syndrome); the procedure is used mainly in women who have had repeated miscarriages or have failed to achieve pregnancy after several IVF treatment cycles, which could be due to the presence of such abnormalities in the embryo. PGD can also be used to detect defective genes responsible for hereditary disorders (e.g. the commonest form of cystic fibrosis, Huntington’s disease) and genes associated with susceptibility to certain cancers. When a defect is detected, *genetic counselling is offered.... preimplantation genetic diagnosis

(antenatal diagnosis) diagnostic procedures carried out on pregnant women in order to detect the presence of genetic or other abnormalities in the developing fetus. Ultrasound scanning (see ultrasonography) remains the cornerstone of prenatal diagnosis. Other procedures include chromosome and enzyme analysis of fetal cells obtained by *amniocentesis or, at an earlier stage of pregnancy, by *chorionic villus sampling (CVS). Noninvasive prenatal diagnosis involves a blood test to analyse cell-free fetal DNA in maternal blood. It can be performed during the first trimester and is used for fetal rhesus (Rh) determination in Rh-negative mothers, fetal sex determination in pregnancies at risk of sex-linked disorders, and for some single-sex gene disorders (e.g. achondroplasia). Compare prenatal screening.... prenatal diagnosis