Non-Invasive Prenatal Testing: For everyone?

REALLY???

Michelle Y. Owens, MD

Maternal Fetal Medicine

• I have no financial disclosures.

Objectives

• Differentiate between NIPT and other antenatal screening tests.

• Discuss the application of NIPT in the evaluation of high risk women.

• Discuss the limitations of NIPT.

Diagnostic versus screening tests

• A diagnostic test determines the presence or absence of a disease when a subject shows signs or symptoms of the disease.

• A screening test identifies asymptomatic individuals who may have the disease.

• The diagnostic test is performed after a positive screening test to establish a definitive diagnosis.

Simple Stats

• Sensitivity: Correctly identify affected individual (true positive rate)

• Specificity: Correctly identify disease-free individual (true negative rate)

Types of Prenatal Testing

• Invasive testing (Diagnostic)

– Chorionic villus sampling (CVS)

– Amniocentesis

– Percutaneous Umbilical Cord Blood Sampling (PUBS)

– Chromosomal Microarray

• Non-Invasive testing

– Maternal serum analyte screening

• First trimester

• Second trimester

– Cell free fetal DNA/RNA

– Ultrasound

• Nuchal translucency

• Targeted sonogram

Ultrasound screening options

• Nuchal translucency

– 10w4d-13w6d

– Increased NT: risk for aneuploidy, CHD, and adverse pregnancy outcomes

– DS DR: 60-82%

– T18 DR: 71-82%

– No ONTD risk assessment

• Fetal anatomic survey

– 18-20w6d (ideal)

– Structural defects, soft markers

– DS DR: 50-70%

– T18 DR: 80%

– ONTD risk assessment

First trimester aneuploidy screening options

• NT only

– 10 4/7-13 6/7

– Detection rates (DR): 80%

• First trimester analyte screening

– PAPP-A, free β-hCG

– 9-13 6/7weeks

– DR Down: 62-63%

– DR T18: 82%

– Does not address ONTD

• Combined first trimester screening

– NT plus analytes

– 9-13 6/7 weeks

– DSDR: 78-91%

– T18 DR: 91-96%

– No ONTD risk

Aneuploidy screening options

• Integrated

– 1st and 2nd trimester analytes (9-13w6d, 15-21w6d) + NT

– DS DR: 94-96%

– T18 DR: 91-96%

– ONTD risk assessment

– Results not given until second trimester

• Serum Integrated

– 1st and 2nd trimester analytes (9-13w6d, 15-21w6d)

– DS DR: 87-88%

– T18 DR: 82%

– ONTD Risk assessment

– Results not given until second trimester

Aneuploidy screening options

• Stepwise sequential

– All maternal serum analytes (9-13w6d, 15-21w6d) + NT

– 1st trimester result for highest risk patients

– DS DR: 91-95%

– T18 DR: 91-96%

– ONTD risk assessment

• Contingency

– All maternal serum analytes (9-13w6d, 15-21w6d) + NT

– 1st trimester results for high and low risk patients, low and moderate risk groups require second visits.

– DS DR: 91-92%

– T18 DR: 91-96%

– ONTD risk assessment

Aneuploidy screening options

• Multiple marker serum screening (Triple, Quad, Penta)

– AFP, hCG, uE3, DIA, +/-ITA (15-21w/6d)

– DS DR: 72-83%

– T18 DR: 60-70%

– ONTD risk assessment

• Non-invasive prenatal testing

– 10-21w6d

– Circulating cell free fetal DNA (cfDNA)

– DS DR: 99-100%*

– T18 DR: 97-100%*

– No ONTD risk assessment

NIPT: The Physiology Basics

• Fetal genetic material can be found in the maternal circulation.

– Fetal cells and cell-free fetal DNA/RNA (cfDNA).

• Fetal DNA comprises 10-15% of the total DNA in the maternal circulation.

Physiology

• The primary source of cfDNA is the placenta (syncytiotrophoblasts).

• The primary source of cfmDNA is apoptotic hematopoietic cells.

Physiology

• Can be detected from 4 weeks gestation.

• Rapid clearance

• Pure fetal DNA extraction from the maternal circulation is not currently possible.

NIPT – The basics

• Uses circulating cell free fetal DNA in maternal plasma to evaluate for T21, T18, and T13.

• Low FPR (<1% ) and very high DR for DS (99-100%), T18 (97-100%) and T13 (79-92%)

Applications of NIPT

• Fetal gender determination

• Rhesus typing

• Single gene disorders

• Aneuploidy testing

High Risk or Low Risk?

• Nicolaides, et al (Ultrasound Obstet Gyneol 2013) FMF

– 1005 women (37), 10 wks gestation, one center

– cfDNA superior to standard screening

• Song, et al (Prenat Diagn 2013)

– 1741 pregnant women <35 yo , 2 clinical sites

– cfDNA testing vs. standard screening

• Sensitivity (100% vs. 54.5%)

• Specificity (99.9% vs. 85.9%)

• PPV (91.7% vs. 2.4%)

High Risk or Low Risk?

• Comparison of Aneuploidy Risk Evaluations (CARE study) – NEJM 2014

– 1914 women (30) , 21 centers

– T21 and T18 Sensitivity (100% vs. 100%)

– T21 Specificity (99.7 vs. 96.4)

– T21 PPV (45.5% vs. 4.2%)

– T21 and T18 NPV (100% vs. 100%)

– T18 Specificity (99.8% vs. 99.4%)

– T18 PPV (40% vs. 8.3%)

Low Risk: Cell-free DNA Analysis for Noninvasive Examination of Trisomy (NEXT)

• 18,955 enrolled 15,841 analyzed

• Pregnant women of all risk levels (76% under 35) – Avg 12.5 weeks

• Testing had higher sensitivity and specificity than standard first trimester screening (FTS) detection of T21.

• FPR was over 90 times lower than that of standard FTS (0.06% vs. 5.4%).

The recommendations: ACOG

• NIPT that uses cfDNA offers tremendous potential as a screening tool for fetal aneuploidy.

• cfDNA testing should be an informed patient choice after pretest counseling and should not be a part of routine laboratory assessment.

ACOG recommendations

• Should not be offered to women with multiple gestations because it has not been sufficiently evaluated in these groups.

• A negative cfDNA test does not ensure an unaffected pregnancy. A patient with a positive result should be referred for genetic counseling and should be offered prenatal diagnosis for confirmation of test results.

SMFM 2014

• While NIPT is a promising new technology, [the available data] is not enough to change the current recommendations. Further evidence… is required to justify changing recommendations regarding population based prenatal screening from just high-risk pregnancies, to all pregnancies.

SMFM (October 2015)

• For front-line clinicians, challenges still exist for determining the most appropriate implementation of cell free DNA (cfDNA) aneuploidy screening. The purpose of this statement is to clarify that SMFM does not recommend that cfDNA aneuploidy screening be offered to all pregnant women, nor does it suggest a requirement for insurance coverage for cfDNA screening in women at low-risk of aneuploidy.

ISUOG (Consensus Statement)

• In very high risk women, NIPT should not replace invasive testing.

• In presence of fetal anomaly, NIPT should not change invasive indications.

• If normal NIPT, “genetic sonogram” should not be performed.

What constitutes “High Risk”?

• Advanced maternal age

• Positive maternal serum screen

• Positive family history

• Parent carrying balanced robertsonian translocation

• Fetal anomaly identified on ultrasound/increased risk of aneuploidy

The Challenges

• Need for professional standards and guidelines

• Non-informative results (NIPT), clinical meaning of copy number (CNV) variants in microarrays

• Resource allocation

• Advanced training and education for providers

• Direct-to-consumer testing

• Detection of mistaken paternity and incest

• Confidentiality of information obtained

• Coercion to have test

• Role of industry promoting research

• Legal concerns (IP)

Things to remember:

• NIPT is a screening test.

• Remember ONTD.

• Serum screening does not replace ultrasound screening.

The Future……

• Further expansion in single gene disorders

• Expansion to include additional chromosome abnormalities

• Potential use in microarray analysis

• Possibly as diagnostic testing

Summary

• Cell free fetal DNA found in maternal blood during pregnancy can be used for non-invasive prenatal diagnosis.

• NIPT is a screening test. Appropriate counseling and diagnostic testing for confirmation is needed for any positive result and should be considered in cases of “no call” test results.

Summary

• This technology offers safer, earlier, and easier antenatal testing than current standard practice.

• Research into non-invasive prenatal diagnosis is ongoing, and the public and healthcare professionals must be kept informed about the progress and limitations of this technology.

Summary

• NIPT does not replace ultrasound. However, ultrasound should not be used as a screen for aneuploidy when NIPT results are known.

• Likewise, the use of multiple serum screening tests is not recommended.

The End!!

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