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Screening

Testing people who do not have or have not recognised the signs or symptoms of the condition being tested for, either with the aim of reducing risk of an adverse outcome, or with the aim of giving information about risk.

Read more on the What is Screening? page of this website.

Screening procedure

See screening test, below.

Screening programme

The whole system of activities needed to deliver high quality screening. It ranges from identifying and informing those to be offered screening through to the treatment and follow up of those found to have abnormality, and support for those who develop disease despite screening.

Screening test

A test or inquiry used on people who do not have or have not recognised the signs or symptoms of the condition being tested for. It divides people into low and higher risk groups.

Secondary prevention

Treatments used in people with a disease in order to reduce the consequences of the condition. Screening is an example.

Sensitivity

This is a measure of test performance. High sensitivity means that the test ‘catches’ as many people with the condition as possible. It is measured as the proportion of those with the condition, who have a positive test result. It is the same as the detection rate.

Sensorineural hearing loss

Hearing loss due to a problem or disorder of the inner ear or of the auditory nervous system.

Serum Integrated Test

The serum integrated test is performed in two stages. In the first stage, at around 11 weeks of pregnancy, the gestation of the pregnancy is determined and a blood sample is taken from the mother to measure the concentration of serum pregnancy associated plasma protein-A (PAPP-A). The second stage involves a second blood sample, ideally taken at 15 or 16 weeks of pregnancy. Only after this second stage is a statistical result given. This blood sample measures four serum levels – alpha feto protein (AFP), unconjugated oestriol (uE3), free beta human chorionic gonadotrophin (freeß-hCG) and inhibin-A (inhibin). The measurement of the total six markers together with the mother’s age are used to estimate her chances of having a pregnancy with Down’s syndrome. Women with a chance greater than 1 in 200 are usually offered amniocentesis.

Severe hearing loss

Hearing loss of between 71 and 95 deciBels averaged across the main frequency range for speech.

Sex chromosomes

The X and Y chromosomes in humans that determine their sex. Females have two X chromosomes (XX); males have an X and a Y chromosome (XY). The sex chromosomes comprise the 23rd chromosome pair in a karyotype.

Sex-influenced

A disorder or characteristic whose expression or severity differs between the sexes. That is, it occurs more frequently or with greater severity in either males or females.

Sex-limited

A disorder or characteristic that is expressed in only one sex. That is, it occurs only in males or in females.

Sex-linked

A disorder or characteristic which is determined by genes carried on the X chromosome. eg Duchenne muscular dystrophy and haemophilia

Sickle cell anaemia (SS)

A usually severe sickle cell disorder (see definition below) caused by inheritance of two genes for haemoglobin S.

Sickle cell disease

The group of inherited conditions that are characterised by sickling of red blood cells when there is a shortage of oxygen. The commonest are sickle cell anaemia (SS), haemoglobin SC disorder, and haemoglobin S/beta thalassaemia. Sickle cell disorders can cause anaemia, increased risk of infections, chest problems and painful crises (unpredictable attacks of very severe pain, that can occur anywhere in the body.) They can be life-threatening, particularly for young children.

Sickle cell carrier (also known as trait)

The presence of one copy of the gene for sickle cell disorder and one unaffected copy in an individual. People with sickle cell trait are unaffected by the condition, but may pass it on to their children if the other parent also has sickle cell trait or sickle cell disorder.

Single-gene disease

A hereditary disorder caused by an altered allele of a single gene (eg PKU, cystic fibrosis, sickle cell disease).

Specificity

This is a measure of test performance. High specificity means the test has as few false positives as possible. It is measured as the proportion of those without the condition, who have a negative test result.

Spina bifida

See neural tube defect.

Stem cell

A precursor cell that can develop into more than one kind of cell. For example, early bone marrow cells can develop into red blood cells, white blood cells or platelets.

Surveillance

Ongoing observation of the health of individuals or populations.

Syndrome

Combination of symptoms and signs grouped together to form a disorder.