Non-Invasive Prenatal Testing

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Non-Invasive Prenatal Testing
Developed by Dr. June Carroll, Ms. Shawna
Morrison and Dr. Judith Allanson Special thanks
to the Childrens Hospital of Eastern Ontarios
Prenatal Genetics Team Last updated April 2014
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Disclaimer

• This presentation is for educational purposes
  only and should not be used as a substitute for
  clinical judgement. GEC-KO aims to aid the
  practicing clinician by providing informed
  opinions regarding genetic services that have
  been developed in a rigorous and evidence-based
  manner. Physicians must use their own clinical
  judgement in addition to published articles and
  the information presented herein. GEC-KO assumes
  no responsibility or liability resulting from the
  use of information contained herein.

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Objectives

• Following this session the learner will be able
  to
• Refer to their local genetics centre and/or order
  genetic testing appropriately for prenatal
  screening
• Discuss and address patient concerns regarding
  prenatal screening
• Facilitate patient informed decision making
  regarding prenatal screening options
• Find high quality genomics educational resources
  appropriate for primary care

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Case 1

• A 32 year old woman has had a positive Integrated
  Prenatal Screening Test (IPS) result for Down
  syndrome. She is about 17 weeks gestation.
• Is NIPT a good option?

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Case 2

• A 40 year old G1 woman is about 9 weeks
  gestation. She is in your office to discuss
  prenatal testing options in this pregnancy
  conceived by IVF.
• Is NIPT a good option?

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Case 3

• A 36 year old G1P0 woman is very anxious about
  Down syndrome in this pregnancy because she had a
  second cousin with Down syndrome who passed away
  as a child.
• Is NIPT a good option?

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Case 4

• A 29 year old patient had a nuchal translucency
  (NT) of 4.4mm at 125 weeks gestation
• You offered NIPT and she accepted
• NIPT results were normal. She is now 142 weeks
  gestation
• What are the next steps?

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Prenatal Screening tests forDS, T18, T13 and
ONTD
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What is Non-Invasive Prenatal Testing?

• Screening test to prenatally detect Down syndrome
  and other aneuploidies (extra or missing
  chromosomes)
• trisomy 21, 18, 13
• trisomy of sex chromosomes (XXX, XXY, XYY)
• Turner syndrome (monosomy X)
• triploidy (extra copy of all chromosomes)

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Non-Invasive Prenatal Testing (NIPT)

• NIPT measures circulating cell-free DNA (cfDNA)
  from placenta present in maternal blood
• Comprises 10 of DNA in maternal blood
• Increases with gestational age
• Companies offering NIPT use various technologies
  to analyze cfDNA and determine chromosome
  quantities
• Performed on maternal blood sample
• As early as 9 weeks gestation (company specific)
• Dating U/S viability, accurate GA, exclude
  multiples

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How good is Non-Invasive Prenatal Testing?

• Moving target
• Currently literature is primarily from companies
  or those holding patents

Overall ranges Overall ranges Overall ranges
T21 T18 T13
Specificity () 99-100 99-100 99-100
Sensitivity () 98-100 97-100 79-100
Positive Predictive Value PPV () 90-95 84 52
Negative Predictive Value NPV () 99.9 99 100
ASHG Oct 2013 platform presentation data from
BGI China 63,543 pregnancies
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What is the evidence for Non-Invasive Prenatal
Testing (NIPT)?

• Studies emerging in low-risk population
• Performance of NIPT in a general obstetrical
  population
• False Positive Rate (FPR) for T21 and T18
  combined was 0.5 vs 4.2 for standard screening
• Positive Predictive Value (PPV) was
  significantly higher than that for standard
  screening, for both trisomy 21 (45.5 vs. 4.2)
  and trisomy 18 (40.0 vs. 8.3)

Bianchi et al, NEJM 2014 3709
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What is the evidence for Non-Invasive Prenatal
Testing (NIPT)?

• 7 studies of high risk women
• High risk
• Screen (IPS, FTS) positive
• AMA (35 yrs)
• Ultrasound findings suggestive of aneuploidy
• Previous pregnancy with aneuploidy

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What is the evidence for Non-Invasive Prenatal
Testing (NIPT)?

• By far most accurate performance for T21/18

Benn et al, Ultras Obstet Gynecol 2013, 42 15-33
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What do the experts say?

• Society of Obstetricians Gynecologists of
  Canada 2013
• Non-invasive prenatal testing using massive
  parallel sequencing of cell-free DNA to test for
  trisomies 21, 18, and 13 should be an option
  available to women at increased risk in lieu of
  amniocentesis. Pre-test counselling of these
  women should include a discussion of the
  limitations of non-invasive prenatal testing.

Genetics Ctte Technical Update JOGC Feb 2013
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What do the experts say?

• Society of Obstetricians Gynecologists of
  Canada 2013
• No irrevocable obstetrical decision should be
  made in pregnancies with a positive non-invasive
  prenatal testing result without confirmatory
  invasive diagnostic testing.

Genetics Ctte Technical Update JOGC Feb 2013
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Recommendations

• Offer all women
• Prenatal screening using either FTS, IPS or MSS
  (SIPS or Quad)
• Fetal morphology scan at 18-20 weeks gestation

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Consider discussing Non-Invasive Prenatal
Testing (NIPT) as an option for women who

• Are of advanced maternal age , defined as 40
  years of age or older at estimated date of birth
• Have an abnormal multiple marker screen i.e.
  FTS/IPS/MSS
• Have fetal nuchal translucency (NT) measurement
  of 3.5mm or greater 
• Have had a previous pregnancy or child with
  aneuploidy
• Have other high risk factors
• Fetal congenital anomalies on ultrasound highly
  suggestive of trisomy 13, 18 or 21
• Soft markers on ultrasound which are highly
  suggestive of aneuploidy Refer to SOGC
  guidelines, 2005.
• At risk of carrying a male fetus with an X-linked
  condition (NIPT would be used for sex
  determination)
• In Ontario, MOHLTC funding applications for the
  indications above marked by an asterisk () must
  be submitted by a geneticist or maternal fetal
  medicine (MFM) specialist. In other provinces
  circumstances may be different. Consult your
  local genetics centre or MFM specialist.

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Non-Invasive Prenatal Testing (NIPT) results

• Results will be reported differently and may be
  worded as
• positive or negative
• aneuploidy detected, no aneuploidy detected or
  aneuploidy suspected/borderline value
• high risk or low risk

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Non-Invasive Prenatal Testing (NIPT) results

• If the result is negative, this is reassuring
• Your patient should still be offered
• MS-AFP between 15 and 206/7 weeks to screen for
  open neural tube defect, as NIPT does not screen
  for this physical anomaly
• fetal morphology scan at 18-20 weeks gestation
• referral for genetic and/or maternal fetal
  medicine consultation, which may be indicated for
  additional counselling and testing, depending on
  the reason your patient qualified for NIPT (e.g.
  increased NT, other soft markers, congenital
  anomalies)

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Non-Invasive Prenatal Testing (NIPT) results

• If the result is positive
• Genetic counselling
• Confirmation by diagnostic testing
• No irrevocable obstetrical decisions should be
  made in pregnancies with abnormal NIPT results
  without confirmatory invasive testing (CVS or
  amniocentesis) - SOGC

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Benefits of Non-Invasive Prenatal Testing (NIPT)

• Fewer women having diagnostic tests with
  associated risk of pregnancy loss
• Early test result (drawn at 9-10 weeks at
  earliest)
• No risk of miscarriage
• Detects the most common chromosomal aneuploidies
• Higher detection rates and lower false positive
  rates than IPS or MSS

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Limitations of Non-Invasive Prenatal Testing
(NIPT)

• NIPT cannot
• Detect chromosome differences other than
  aneuploidy of chromosomes 13, 18, 21, X and Y
• some companies are now adding screening for other
  trisomies and certain microdeletion syndromes
• Completely rule out aneuploidy
• Detect single gene conditions
• Detect congenital anomalies
• Failed results
• 6.1 untested for insufficient sample quality
• 2 no result after testing (rarely happens with
  conventional screening)
• cfDNA decreases with increased maternal BMI, twin
  pregnancies and where trisomy 18 and 13 are
  present
• Limited data on performance in IVF pregnancies

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Limitations of Non-Invasive Prenatal Testing
Confined placental mosaicism

• False positives (and negatives) are possible
• Confined placental mosaicism

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Non-Invasive Prenatal Testing (NIPT) Landscape

• Increasing demand from women
• Increasing uptake in most (urban) centres
• 3 separate companies, 3 separate technologies
• Has NIPT become standard of care?
• Costs between 795 and 1200
• 8-10 days for result

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Where does Non-Invasive Prenatal Testing (NIPT)
fit with respect to the 11 to 14 wk scan?

• 11 to 14 week scan has value to pregnancy care
• Raised NT may suggest other chromosomal, genetic
  and structural disorders
• Accurate dating/establishment of live fetus
• Multiples/chorionicity affects management
• Detects structural abnormalities

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Non-Invasive Prenatal Testing (NIPT) and
counselling

• Pre- and post-test counselling is important
• Consult genetics if unsure
• Refer for genetic counselling when appropriate
• Company websites
• Harmony Prenatal Test by Ariosa Diagnostics
  through Gamma-Dynacare
• Panorama by Natera through Lifelabs
• Verifi Prenatal Test by Verinata

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Ordering Non-Invasive Prenatal Testing (NIPT)

• In Ontario, to order NIPT, first determine your
  patients funding eligibility by looking at the
  MOHLTC checklist, then
• Complete the checklist and pages 2 and 4 of the
  MOHLTC out-of-country testing prior approval form
  
• Download and complete the requisition from the
  NIPT company of your and your patients choice
• Selection may be based on the patients personal
  research and preference, your experience with a
  particular company, ease of access to a blood
  draw location
• Send all three completed forms to the fax number
  613 536-3181 or 1 866 221-3536 and be sure to
  indicate the patient is pregnant so approval can
  be prioritized accordingly
• Once approval has been received, give the patient
  the approval letter and the NIPT requisition and
  she can then have her blood drawn

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Case 1

• A 36 year old woman has had a positive
  Integrated Prenatal Screening Test (IPS) result
  for Down syndrome. She is about 17 weeks
  gestation.
• Is NIPT a good option?

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• Yes
• She is eligible for NIPT with MOH funding
• But consider
• More rapid result from amniocentesis
• What is her IPS risk?
• 1 in 2 versus 1 in 120
• She is at 17 weeks gestational age
• If NIPT is positive, guidelines recommend
  confirmatory diagnostic testing by amniocentesis
  delays timing for diagnosis
• In the event of an abnormal result, is
  termination of pregnancy an option for the
  couple?

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Case 2

• A 40 year old G1 woman is about 9 weeks
  gestation. She is in your office to discuss
  prenatal testing options in this pregnancy
  conceived by IVF.
• Is NIPT a good option?

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• Yes
• Advanced maternal age (greater than 40 years at
  EDB) is an appropriate indication for NIPT
• Covered by MOH funding
• Better screen than IPS
• Earlier result
• Decreased chance with NIPT that patient would
  receive screen positive result

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Case 3

• A 36 year old G1P0 woman is very anxious about
  Down syndrome in this pregnancy because she had a
  second cousin with Down syndrome who passed away
  as a child.
• Is NIPT a good option?

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Case 3

• She does not meet MOH criteria for coverage of
  NIPT
• You can reassure her that having a second cousin
  with Down syndrome does not increase her risk to
  have an affected child
• If she is very anxious, you can proceed with NIPT
  and she can pay out of pocket
• If the patient herself had a previous affected
  pregnancy then she would be eligible for MOH
  funded NIPT

P
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Case 4

• A 29 year old patient had an NT of 4.4mm at 125
  weeks gestation
• You offered NIPT and she accepted
• NIPT results were normal. She is now 142 weeks
  gestation
• What are the next steps?

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• Genetic counselling is recommended
• Patient likely to be offered
• Chromosomal microarray
• Genetic testing for other single gene conditions
• Level II ultrasound
• Fetal echocardiogram

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Prenatal Screening Summary

• Offer all pregnant women, regardless of age
• PN screening for fetal aneuploidy (trisomy 13,
  18, 21) through FTS, IPS, SIPS or Quad screening
• Second trimester ultrasound for dating,
  assessment of fetal anatomy and detection of
  multiples
• Maternal age should not be used as a basis for
  recommending invasive testing when non-invasive
  PN screening is available
• Non-Invasive Prenatal Testing (NIPT)
• Consider offering NIPT to high risk women
• Consider NIPT as a screen of higher sensitivity
  if your patient is willing to pay for the test
• Best for Down syndrome (trisomy 21) (but can be
  wrong!)
• so far, others not as good (T13 and sex
  chromosomes)
• Effectively sampling the placenta (not fetal
  cells directly)
• It is not a diagnostic test
• Not an all purpose genetic test, only gives info
  on specific chromosomes, and so not indicated in
  all circumstances

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Dont forget

• Take a family history to identify familial and/or
  ethnicity-specific disorders and screen
  accordingly
• Consider consanguinity and screen and test
  accordingly
• Refer or consult genetics when in doubt

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Useful Genetics Resources

• GEC-KO website Genetics Education
• www.geneticseducation.ca
• NIPT fact sheets
• http//www.mountsinai.on.ca/care/family-medicine-g
  enetics-program/prenatal
• Prenatal Screening Ontario Website
• http//www.prenatalscreeningontario.ca/
• Society of Obstetricians and Gynaecologists of
  Canada (SOGC) national clinical guidelines in
  prenatal genetics visit http//sogc.org/clinical-p
  ractice-guidelines/ and scroll down to Genetics.