Screening Down Syndrome Prog

Question 1

Definition of Screening?

Answer 1

‘A process of identifying apparently healthy people who may be at increased risk of a disease or condition. They can then be offered information, further tests & appropriate treatment to reduce their risk and or any complications arising from the disease or condition’

UK NSC

Question 2

What is FASP?

Answer 2

NHS Fetal Anomaly Screening Programme: FASP is part of Public Health England & is overseen by UK NSC.

Offers screening to all pregnant women in England to assess risk of T21 & number of fetal anomalies.

Question 3

What is the Scottish Programme?

Answer 3

Scottish Down Syndrome and Fetal Anomaly Screening Programmes:

Scotland screening funded by National Service Division (NSD). & overseen bbt UK NSC

Question 4

What is UK recommended ‘screen positive cut off?

Answer 4

UK recommended cut off is 1:150

Question 5

Screening Terminology!

Prevalence
Sensitivity
Specificity
Detection Rate (DR)
Screen Positive Rate (SPR)
False +be rate (FPR)
False meg rate (FNR)

Answer 5

Prevalence: Number of individuals in a population with condition.

Sensitivity: Screens ability to refer individuals who have target condition (proportion of +bed which are correctly IDs as such)

Specificity: screens ability NOT to refer individuals who do NOT have condition (proportion of -bed who are correctly IFs as such).

Detection Rate: Proportion of affected individuals with positive screening result!

Screen Positive rate: Proportion of individuals who will be give a high risk following screening

False positive rate: Proportion of unaffected individuals with a positive screening result. Specificity = 100 - FPR

False negative rate: Proportion of women who are given a lower risk but have affected pregnancy!

Question 6

When is Nuchal Translucency measured & definition?

Answer 6

• Between 11 & 14 wks
• NT is the max. Thickness of the fluid under the skin at the back of the neck.
• If NT > or equal to 3.5mm pregnancy considered at increased risk.

Question 7

What is the combined Test?

Answer 7

Recommended test: Combines 1st trimester screening & NT!

• B-hCG, PAPP-A & NT
• DR approx 87% for 5% FPR

Preformed between 10-14wks (ideally 11+2)

Question 8

What is the recommended test for women who present too late for combined test?

Answer 8

• Quadruple screening: AFP, B-hCG, uE3 & Inhibin A
• Performed 2nd trimester (14+2-20wks).
• DR ~81% for 5% FPR

Question 9

Which test gives the best DR?

Answer 9

• Integrated rest: DR ~96% for 5% FPR
• PAPP-A, B-hCG, & NT in 1st tri, then AFP, uE3 & inhibit A in 2nd trimester!

However, integrated test NOT recommended as up to 25% women fail to attend 2nd component of test! Prefer single test… And integrated test provides result later than combined test.

Question 10

What factors affect serum testing?

Answer 10

• Markers tend to be decreased in heavier women.
• Higher In Afro-Caribbean than Caucasian
• IVF
• Insulin dependent diabetes
• Smoking
• Approx adjustments to MoM values are made for these factors!

Question 11

What test is recommended for twin pregnancies?

Answer 11

• NICE recommend the Quadruple test for twin pregnancies.

Question 12

Are T13,T18 included in combined test?

Answer 12

Yes: T13,T18 & T21 are all included in combined test.

If a NT was not possible, quadruple test can be performed which only screens for DS!!

Question 13

When is the Fetal Anomaly scan performed?

Answer 13

• Between 18&20wks!

Following should be reported & women referred for further assessment:
- Nuchal fold, ventriculomegaly, echogenic bowel, small measurements compared to dating scan.