Antenatal and newborn screening: Flashcards
Outline the WHO criteria for screening programme and its 4 main areas:
Knowledge of the disease:
- Condition should be important
- There should be a latent or early symptomatic stage
- The natural course of the condition should be understood
Knowledge of test:
- Suitable test or examination
- Test acceptable to population
- Case-finding should be a continuous process
Treatment for disease:
- Accepted treatment for patients with recognised disease
- Facilities for diagnosis and treatment available
- Agreed policy concerning whom to treat as patients
Cost considerations:
- The cost of case finding (including diagnosis and subsequent treatment_ should be balanced by the expenditure on care as a whole
Define screening:
The process of identifying apparently health individuals who may be at an increased risk of a disease or condition. They can then be offered information, further tests and appropriate treatment to reduce their risk, and/or any complications from the disease or condition
Define ‘detection rate’:
Proportion of affected individuals who will be identified by screening test
Define ‘false positive rate’:
Proportion of unaffected individuals with a higher risk/screen positive results
Define ‘false negative rate’:
Proportion of affected individuals with a low risk/screen negative result
Outline the 7 steps of the screening pathway:
1) Identify individuals to be screened
2) Inviting individuals for screening
3) Giving information to individuals and encouraging uptake
4) Undertaking accurate screening
5) Acting of screening results (referral, diagnosis, intervention and treatment)
6) providing support and follow up
7) Optimising health outcomes
What pre-test information should be provided to an individual prior to screening?
- Condition being screened for
- When & how the test is carried out
- How reliable the test is
- Different possible results and their meanings
- Options if the test is positive
List the antenatal screening programmes:
- Foetal Anomaly (Down’s, Edwards, Patau’s)
- Infectious disease
- Haemoglobinopathies (Sickle cell and thalassaemia)
List the newborn screening programmes:
- Newborn blood-spot screening programme
- Newborn hearing programme
- Newborn and 6-8 week infant physical examination programme
What disease are typically covered in the ‘Newborn blood-spot’ screening programme:
- CF
- Congenital hypothroidism
- Sickle cell disease
- Inherited metabolic diseases:
- Phenylketonuria
- MCADD
- Maple Syrup disease
- Isovaleric Acidaemia
- Glutaric Aciduria Type 1
- Homocystinuria
In Downs Syndrome, what chromosomal abnormality is present? What health risks are those with Downs Syndrome at?
Extra copy of chromosome 21.
40-45% have heart defect. Increased incidence of childhood leukaemia, thyroid disorders and Alzheimers.
In Edwards syndrome, what chromosomal abnormality is present?
Extra copy of chromosome 18
What is the life expectancy of those with Edwards syndrome? What abnormalities are often present?
Most babies die before, during or shortly after birth.
Wide range pf medical problems:
- Heart problems
- Unusual facial features
- Major brain abnormalities
In Pataus Syndrome, what chromosomal abnormality is present?
Extra copy of chromosome 13.
What is the life expectancy of those with Pataus syndrome? What abnormalities are often present?
Most babies will die before, during or shortly after birth.
Multiple severe abnormalities:
- 80% congenital heart defect
- Abdominal wall defects
- Urogenital malformations
- Hand and feet abnormalities
Outline the weeks involved in each trimester:
1st: 0-13
2nd: 14-27
3rd: 28- birth
What screening is performed in the first trimester? And when is it offered?
- Nuchal translucency
- Serum testing
Offered when crown-rump length is 45-84mm (around 12 weeks).
What is the normal range of nuchal translucency?
2.5-3.5mm
What serum results from the 1st trimester indicate abnormalities?
PAPP-A:
- Abnormal if low
Free Beta hCG:
- Too high: Downs (T21)
- Too low: Edwards (T18)
When is 2nd trimester screening performed? What is the test called and what does is measure?
Offered when combined screening in first -trimester not available (late booker or NT not obtained)
Called the Quadruple test.
Offered around 17weeks.
Serum only:
- AFP (if high: ?neural tube defects, If low: ?Downs)
- Total Beta hCG
- Oestriol
- Inhibin A
What factors are taken into account with the results calculation?
- Scan measurements
- Mother DOB
- Serum markers
- Levels of some markers affected by ethnicity, smoking and diabetes
- Mothers weight
If a positive screening results is found on during the combined or quadruple tests, what should be done?
1) Telephone to screening midwives
2) Appointed to foetal medicine unit within 3 days
3) Offered Diagnostic tests: CVS and amniocentesis
When are scans scheduled during normal pregnancy and why are they performed?
First scan - 10-14 weeks:
- Dating of pregnancy
- Confirming viability
- Multiple pregnancy
- Nuchal Translucency test
Second scan - 18- 20+6 weeks:
- Structural abnormalities
- Gender
- Conditions which may benefit from treatment before birth
- Plan delivery in an appropriate hospital/centre
- Optimise treatment after the baby is born
- Provide choices for the woman and her family about continuance or termination of pregnancy
When can infectious disease screening be offered?
At any stage, but ideally taken at the earliest opportunity.
