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BusySpR MRCOG PART I - CLINICAL MX & DATA
MRCOG Part 1 , MRCOG I

1400 SBAs. ALL are recalls from last 10 years MRCOG 1 exams.

 
 
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Forum >> MRCOG Part I single best answers: Pre-natal diagnosis
MRCOG Part I single best answers: Pre-natal diagnosis Posted by Farrukh G.
Sun Jul 8, 2012 02:23 pm

 

1) Down’s syndrome is associated with

 

A) Lower maternal serum free beta-HCG in the first trimester

B) Lower maternal serum pregnancy associated plasma protein A in the first trimester  

C) Lower maternal serum AFP in the first trimester

D) Lower maternal serum unconjugated oestradiol in the first trimester

E) Higher maternal serum unconjugated oestradiol in the first trimester

 

 

2) In the second trimester

 

A) Serum AFP levels are lower in women with a fetus with Down’s syndrome  

B) Serum unconjugated oestradiol levels are higher in women with a fetus with Down’s syndrome

C) Fetal serum AFP levels are lower in fetus with Down’s syndrome

D) Fetal serum AFP levels are higher in fetuses with Down’s syndrome

E) Serum unconjugated oestradiol levels are lower in women with a fetus with Down’s syndrome

 

3) Which one is used as part of second trimester biochemical screening for Down’s syndrome?

 

A) Maternal serum unconjugated oestradiol

B) Maternal serum unconjugated oestriol  

C) Maternal serum oestradiol

D) Maternal serum conjugated oestriol

E) Maternal serum unconjugated oestrogen

 

4) Which one is used as part of first trimester screening for Down’s syndrome?

 

A) Maternal serum unconjugated oestriol

B) Maternal serum AFP

C) Maternal serum free beta-HCG  

D) Maternal serum inhibin-A

E) Maternal serum placental growth factor

 

5) Which one is used as part of first trimester screening for Down’s syndrome?

 

A) Maternal serum unconjugated oestriol

B) Maternal serum AFP

C) Maternal serum inhibin-A

D) Maternal serum placental growth factor

E) Maternal serum pregnancy-associated plasma protein A  

 

6) In normal pregnancies between 14 and 20 weeks gestation

 

A) Maternal serum AFP levels fall

B) Maternal serum unconjugated oestradiol levels fall

C) Maternal serum free beta-HCG levels fall  

D) Maternal serum unconjugated oestradiol levels fall

E) Maternal serum oestrogen levels plateau 

 

7) Which one is the most effective maternal serum marker for Down’s syndrome during the second trimester?

 

A) Unconjugated oestradiol

B) Unconjugated oestriol

C) Alpha-fetoprotein

D) Free beta-HCG  

E) Inhibin-A

 

8) Between 11 – 14 weeks gestation

 

A) Maternal serum pregnancy associated plasma protein A levels are unchanged

B) Maternal serum pregnancy associated plasma protein A levels decrease

C) Maternal serum free beta-HCG levels are unchanged

D) Maternal serum free beta-HCG levels decrease  

E) Fetal nuchal transluscency decreases

 

 

9) Maternal serum inhibin-A levels

 

A) Decrease with increasing gestation age after 17 weeks

B) Are higher in women with a fetus affected by Down’s syndrome  

C) Increase with increasing gestation age between 11 – 14 weeks

D) Are unaffected by fetal Down’s syndrome

E) Plateau after 20 weeks gestation

 

10) Increasing maternal weight is associated with

 

A) An increase in maternal serum AFP levels in the second trimester

B) An increase in maternal serum unconjugated oestriol levels in the second trimester

C) A decrease in maternal serum free beta-HCG levels in the second trimester  

D) No change in maternal serum AFP levels in the second trimester

E) No change in maternal serum free beta-HCG levels in the second trimester

 

11) Which one of the factors below is listed with the appropriate effect on maternal serum markers for Down’s syndrome?

 

A) Obesity – increased maternal serum AFP levels

B) Insulin-dependent diabetes mellitus – decreased maternal serum AFP levels  

C) Smoking – decreased maternal serum inhibin-A levels

D) Smoking – increased maternal serum free beta-HCG levels

E) Parity – increased maternal serum AFP levels with increasing parity

 

12) Which one of the factors below is listed with the appropriate effect on maternal serum markers for Down’s syndrome?

 

A) Black ethnic origin – higher maternal serum AFP levels  

B) Black ethnic origin – lower maternal serum free beta-HCG levels

C) Obesity – higher maternal serum free beta-HCG levels

D) IVF pregnancy – lower maternal serum free beta-HCG levels

E) IVF pregnancy – higher maternal serum unconjugated oestriol levels

 

13) Conception through IVF is associated with (TRUE / FALSE)

 

An increased risk of Down’s syndrome  

Higher rate of false positive screening for Down’s syndrome  

Higher maternal serum free beta-HCG levels in the second trimester  

Lower maternal serum unconjugated oestriol levels in the second trimester  

 

 

14) Which one is not used in the integrated screening test for Down’s syndrome

A) Nuchal transluscency

B) Pregnancy associated plasma protein A at 11-14 weeks

C) Free beta-HCG at 11-14 weeks  

D) AFP at 14-20 weeks

E) Unconjugated oestriol at 14-20 weeks

 

15) The integrated test to screen for Down’s syndrome is undertaken at

 

A) 11 – 14 weeks gestation

B) 9 – 11 weeks gestation

C) 14 – 20 weeks gestation

D) 11 – 14 and 14 – 20 weeks gestation  

E) 9 – 11 and 11 – 14 weeks gestation

 

16) Which one is not correct with reference to the Combined screening test for Down’s syndrome?

 

A) Measures nuchal transluscency

B) Measures free beta-HCG

C) Measures pregnancy-associated plasma protein A

D) Measures alpha feto-protein   

E) Is undertaken at 11-14 weeks gestation

 

17) Which one of the statements regarding the Quadruple screening test for Down’s syndrome is not correct?

 

A) Undertaken at 11 – 14 weeks gestation  

B) Measures maternal serum AFP

C) Measures maternal serum unconjugated oestriol

D) Measures maternal serum inhibin-A

E) Measures maternal serum free beta-HCG

 

18) The Triple test used to screen for Down’s syndrome

A) Should not be performed after 15 weeks gestation

B) Measures AFP, HCG and Inhibin-A

C) Measures AFP, HCG and oestrogen

D) Measures AFP, HCG and unconjugated oestriol  

E) Measures AFP, HCG and PAPP-A 

 

19) Which one of these conditions can be diagnosed using fluorescent in-situ hybridization?

 

A) Duchenne muscular dystrophy

B) Sickle cell disease

C) Patau’s syndrome  

D) Cystic fibrosis

E) Tay-Sach’s disease

 

 

 

 

Posted by PAUL A.
Sun Jul 15, 2012 02:19 pm

 

  1. B
  2. A
  3. B
  4. C
  5. E
  6. C
  7. D
  8. D

Serum screening for Down’s syndrome

  • Downs syndrome associated with raised first trimester free b-HCG and low Pregnancy associates plasma protein A (PAPP-A) in the first trimester
  • First trimester screening is undertaken at 11-14 weeks gestation and uses a combination of nuchal transluscency (NT), free beta-HCG and PAPP-A
  • Between 11 – 14 weeks, PAPP-A and NT increase, while free beta-HCG decreases.
  • On average, second trimester MSAFP is 25% lower in women with a fetus with Downs compared to those with a normal fetus
  • There is, however, no difference in fetal serum AFP concentration in Downs
  • Maternal second trimester serum unconjugated oestriol (MSuE3) ~ 25% lower in Downs
  • Second trimester serum free b-HCG is the most effective marker for Downs in maternal serum - concentrations ~2X normal in Downs

Note that MSAFP and MSuE3 rise between 14-21 weeks while HCG concentrations fall over this period. Inhibin-A decreases before 17 weeks and increases after 17 weeks.

9) B

  • Note that MSAFP and MSuE3 rise between 14-21 weeks while HCG concentrations fall over this period. Inhibin-A decreases before 17 weeks and increases after 17 weeks.
  • The placenta in Downs syndrome is thought to behave as a functionally immature placenta
  • Maternal second trimester serum Inhibin-A is increased (1.79 MoM) in Downs syndrome
  • Trisomy 18 (Edward’s syndrome) is associated with low maternal serum AFP, free beta-HCG and uE3
  • Need accurate dating of pregnancies to optimise sensitivity of second trimester screenin

10) C

11) B

12) A

 

FACTORS AFFECTING SERUM MARKERS

  • Maternal weight - 20kg increase in maternal weight associated with 17% decrease in MSAFP, 7% decrease in MSuE3 and 16% decrease in MSHCG
  • IDDM - MSAFP 10% lower (after correction for weight), MSuE3 7% lower, Inhibin-A 9% lower. Total MSHCG not significantly different
  • Twin pregnancy - serum markers 2X singleton pregnancies
  • Ethnic origin - MSAFP and MSHCG 10% higher in blacks (incidence of neural tube defects ~50% lower in blacks)
  • Smoking - inhibin-A levels 40% higher in smokers, MSHCG 20% lower in smokers. Adjusting for smoking makes little difference to screening performance
  • Parity - MSHCG falls with increasing parity - 3% for each previous birth

Assisted reproduction - IVF associated with higher false positive rate for Downs syndrome. MSHCG higher and MSuE3 lower

 

 

13) Conception through IVF is associated with

 

An increased risk of Down’s syndrome  F

Higher rate of false positive screening for Down’s syndrome  T

Higher maternal serum free beta-HCG levels in the second trimester  T

Lower maternal serum unconjugated oestriol levels in the second trimester  T

 

14) C

15) D

16) D

17) A

18) D

SCREENING TESTS

 

Integrated test

 

NT and PAPP-A at 10 completed weeks gestation + AFP, free beta-HCG, uE3 and Inhibin-A at 14-20 weeks gestation

Most effective screening test with a false positive rate of 1.2% (1.0 - 1.4) for an 85% detection rate

Serum integrated test

Integrated test without NT

Second most effective test with a 2.7% false positive rate (2.4 - 3.0) for an 85% detection rate

Combined test

NT, free beta-HCG and PAPP-A at 10 completed weeks gestation

6.1% (5.6 - 6.5) false positive rate for an 85% detection rate

Quadruple test

AFP, uE3, free beta-HCG and Inhibin-A at 14-20 weeks gestation

6.2% (5.8 - 6.6) false positive rate for an 85% detection rate

Triple test

AFP, uE3, free beta-HCG at 14 - 20 weeks gestation

9.3% (8.8 - 9.8) false positive rate for an 85% detection rate

Double test

AFP and free beta-HCG at 14-20 weeks gestation

13.1% (12.5 - 13.7) false positive rate for an 85% detection rate

NT measurement

At 12-13 completed weeks gestation

20% (18.6 - 21.4) false positive rate for an 85% detection rate

 

 

19) C

RAPID PRE-NATAL DIAGNOSIS: TECHNIQUES

 

The availability of rapid diagnostic techniques has led the UK National Screening Committee to recommend that screening programmes for Downs syndrome need no longer include karyotyping

 

Karyotype is typically available after 2-3 weeks while results of rapid diagnostic tests can be available within 24-48h. However, rapid tests only analyse specific chromosomes, typically 13, 18, 21 and X & Y if required

 

Fluorescence in-situ hybridisation (FISH)

 

• Uses non-dividing (interphase) cells in uncultured samples

 

• Fluorescently labelled chromosome-specific DNA sequences are used to identify chromosome copy number

 

• Three chromosomes can be detected at the same time (three flurochromes available - red, blue and green)

 

• Commercial kits are available for FISH and this is therefore a relatively inexpensive technique

 

• Designed to detect specific aneuploidies and will not detect other abnormalities or structural chromosomal defects

 

• False positive rate less than 1 in 30,000 cases

 

• False negative rate less than 1 in 4000 cases

 

• Misdiagnosis may be due to:

 

1) Maternal cell contamination - this will not be detectable if the fetus is female.

 

2) Structural chromosome anomalies

 

3) DNA polymorphism causing cross-hybridisation of DNA probe with other DNA locations

 

4) Mosaicism - this may only be detected if a sufficient cells (at least 100) are used for analysis