Screening and Diagnostic tests Flashcards
What trisomies do screening tests detect? (3)
21, 18 + 13
When are screening tests offered?
To all women at their booking visit
What is the recommended screening test in the UK?
Combined test
What does the combined screening test look for? (4)
- Nuchal transluscency (NT)
- hCG
- PAPP-A (pregnancy-associated plasma protein)
- women’s age
At what dates do you do the combined test? (2)
11 and 13 weeks + 6 days
What is good about the combined screening test? (2)
results available in the 1st trimester so allows surgical TOP.
it detects all aneuoploidies
What test is rarely used in the UK as it is expensive?
Integrated test
looks at:
1st trimester = NT + PAPP-A
2nd trimester = Quadruple test
What two tests are useful for women presenting in the second trimester?
Triple test and Quadruple test
15-20 weeks
What does the Triple test look for? (3)
AFP \+ unconjugated oestrodiol \+ hCG
What does the qaudruple test look for? (4)
AFP \+ Unconjugated oestrodiol \+ hCG \+ inhibin A
What does AFP screen?
Neural tube defects
At what weeks do you use an US to assess nuchal translucency?
11 - 13 weeks
When is nuchal transluscency raised?
in trisomy conditions
+
structural defects - congenital cardiac deformities
How can neural tube defects be picked up? (2)
on USS
or
by measuring AFP in the 2nd trimester
What does screening aim to identify
women at high risk (usually greater than 1 in 150) of a disorder:
higher risk diagnostic test can then be arranged
What are two types of diagnostic tests?
- Amniocentesis
2. Chorionic villous sampling
When is Amniocentesis performed?
16 weeks
What does amniocentesis involve?
what does it allow diagnosis of? (3)
removal of around 20ml of amniotic fluid using a fine gauge needle under US guidance.
Allows diagnosis of chromosomal abnormalities, NTDs and inborn errors of metabolism.
When is chorionic villous sampling carried out?
10-13 weeks
How is chorionic villous sampling done?
placenta is sampled by transabdominal or occoasionally transcervical approach under US
