prenatal(screening(in(2017— the(dos(and(the(don’ts...t18 t13 sca rare(trisomy translocation...

Prenatal Screening: Biggio UAB Progress in OBGYN 2017

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Prenatal Screening in 2017—The DOs and the DON’Ts

Joseph R. Biggio, MDUniversity of Alabama at BirminghamMaternal Fetal Medicine and Genetics

Disclosures

• No financial conflicts to report

Learning Objectives

• Discuss differences between cfDNA screening and conventional screening

• Review performance and limitations of cfDNAscreening compared to conventional screening for common aneuploidies and all chromosome abnormalities

• Identify key components of informed consent as well as pre-‐ and post-‐test counseling

ACOG Practice Bulletin #163

• Maternal age should not be sole factor in offering diagnostic test• Aneuploidy screening or diagnostic testing should be offered to all women early in pregnancy

Integrated Screening

• A combination of 1st and 2nd trimester screening tests• 11-‐13 weeks: NT, PAPP-‐A• 15-‐17 weeks: AFP, hCG, estriol, & inhibin

• Final result provided once Quad screen completed

• All testing combined into a SINGLE result

Malone et al., NEJM, 2005;; 353:2001-11


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68 69

8185 86

95

NT Triple Quad NT + PAPPA + hCG

PAPPA + Quad

NT + PAPPA + Quad

Detection Rate for 5% Screen Positive Rate

Integrated tests

Non-‐Invasive Prenatal Testing (NIPT)OR

Non-‐Invasive Prenatal Screening (NIPS)OR

Cell-‐free DNA Screening for Aneuploidy

Placenta Maternal plasma Maternal blood cells

•Cell-free fetal AND maternal DNA fragments in maternal plasma •Placenta→ Fetal DNA•Reliably detected >10 weeks gestation•Gone by 2 hr postpartum

•Blood cells, soft tissue, tumors→Maternal DNA•Fetal DNA: 5-25% (~15%) total cell-free DNA

Lo, Lancet 1997;350:485-‐487

Using cf-DNA screening in your practiceThe DOs and the DON’Ts

The DOs

1. Provide patients with appropriate pre-‐test and post-‐test counseling

2. Refer patients who receive a high-‐risk result for counseling and possible diagnostic testing

3. Order AFP only, NOT a QUAD, in the second trimester for assessment of NTD risk in patients who have had cf-‐DNA screening

4. Offer cf-‐DNA to high risk groups as an option for screening

The DON’Ts1. Don’t tell patients that cf-‐DNA will detect all chromosome

abnormalities and that their fetus is normal if the result is normal

2. Don’t order cf-‐DNA screening in low-‐risk groups just so the patient can finder out gender earlier

3. Don’t order microdeletion panels as part of cf-‐DNA screening

4. Don’t ignore ’No call’ or ‘equivocal’ results; refer patients for counseling and further evaluation

5. Don’t use cf-‐DNA as a replacement for diagnostic testing, especially in the setting of U/S abnormalities

6. Don’t order a targeted U/S in AMA patients if the patient has a low-‐risk cf-‐DNA result and there are no other indications for scan.


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DO order AFP only, NOT a QUAD, in the second trimester for assessment of NTD risk in patients who have had cf-‐DNA screening

Origins of Maternal Serum Screening

• Neural tube defects–1970s elevated AFP in amniotic fluidàserum• Brock et al, 1973; Wald et al, 1974

• Aneuploidy screening a result of serendipity and ingenuity•Merkatz et al, 1984

AFP• Elevated– Disruption of fetal-‐maternal-‐placental barrier– Placental vascular damage– Impaired integrity of fetal skin

• Disorders– Neural tube defects– Ventral wall defects– Dermatologic disorders – Congenital nephrosis

AFP for NTD and VWD

• Unclear incremental benefit with modern US for NTD detection–Questionable need in severe lesions–Potential role for distal or difficult to visualize lesions• 9 out of 12 missed cases of NTD, AFP not done—Racusin et al, Am J Perinatol, 2015

• US identifies most VWD

DO offer cf-DNA to high risk groups as an option for screening

DON’T order cf-DNA screening in low-risk groups just so the patient can finder out gender earlier

WHAT IS THE APPROPRIATE POPULATION FOR CELL-FREE DNA TESTING?


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• Appropriate Populations:• AMA• Prior affected• Abnormal screen • Ultrasound abnormality• Robertsonian translocation involving 13 or 21

• Pre- and post-test counseling• Need more information for multiples

Comparison of prenatal screening and diagnostic test options

Test Detection rate for DS

(%)

Screenpositive rate

(%)

PositivePredictive Value (%)

First trimester screen 80 5 ~3

Sequential/Integratedscreen

93 5 ~4-‐6

Cell-‐free DNA screen 99 1-‐9

(in cludes no cal l /test

fai lu res)

40-‐88%

Chorionic Villus Sampling >99 1 (in cludes mosaicism)

Amniocentesis >99 0.2 (in cludes mosaicism)

Adapted from SMFM Consult Prenatal aneuploidy screening with cfDNA. Am J Obstet Gynecol 2015.

Test Comparison: High vs Low Risk

• Prevalence 1 in 1,000–10 will have aneuploid fetus

• Detect 10 aneuploid • 9 false positive

PPV=10/19=53%

• Prevalence 1 in 100–100 will have aneuploid fetus

• Detect 99 aneuploid• 9 false positive

PPV=99/108=92%

In a population of 10,000 womenDetection rate 99.7%, false positive rate 0.1%

DON’T ignore ’No call’ or ‘equivocal’ results; refer patients for counseling and further evaluation

“No call” results (screening failure)

• Not reported, indeterminate, or uninterpretable results

• Occurs in 1-‐8% of patients• 50-‐60% of repeat screens will provide a result

No result significance

• Uninterpretable results associated with• Aneuploidy• Vanishing twin• Maternal malignancy• Mosaicism• Low fetal fraction

• Increased risk of aneuploidy• 20-‐25% prevalence

Pergament et al, O&G 2014; Norton et al, NEJM, 2015


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• Follow-‐up• Genetic counseling• Targeted ultrasound• Repeat cfDNA testing consideration• 50% get interpretable result• Gestational age and options considerations

• Offer diagnostic testing

DON’T tell patients that cf-‐DNA will detect all chromosome abnormalities and that their fetus is normal if the result is normal

DON’T use cf-‐DNA as a replacement for diagnostic testing, especially in the setting of U/S abnormalities

Current cf-‐DNA platforms: Conditions routinely screened for

• Down syndrome• Trisomy 18 (Edward syndrome)• Trisomy 13 (Patau syndrome)• Sex chromosome aneuploidy (most labs)• Turner syndrome• Klinefelter syndrome• XXX• XYY

Limitations of cf-‐DNA for detection of chromosome abnormalities

• Proportion of chromosome abnormalities due to common trisomies (13,18, 21) depends on population risk, especially maternal age• Ranges from 60-‐75%

• Cannot differentiate mode of inheritance and recurrence risk• Non-‐disjunction trisomy• Translocation• Mosaic

53%

13%

5%

8%

5%

16%

T21T18T13TurnerSex trisomyOther

Distribution of chromosome abnormalities: Livebirths, Fetal death >20

weeks, TOP for anomalies

Adapted from Wellesley et al. , Eur J of Hum Gen, 2012

1st Trimester/Integrated Screening vs cf-‐DNA: Performance in a high-‐risk cohort

• 68,990 screen-‐positive• 26,059 (38%) diagnostic testing• 2,993 (11.5%) abnormal result•83.1% (n=2487) Trisomy 13, 18, 21, sex chromosome aneuploidy—DETECTABLE•16.9% (n=506) UNDETECTABLE—mosaic, triploid, translocation, marker, other

Norton et al, Obstetrics & Gynecology, 2014


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Distribution of chromosome abnormalities (n=2,993)

53%

17%

5%

8%

5%3% 3% 1%

5%T21T18T13SCAMosaicRare trisomyTranslocationTriploidyOther

16.9% 1st Trimester/Integrated Screening vs cf-‐DNA: Performance in a high-‐risk cohort

• 2% of screen positive patients had an abnormal result not detectable by cf-‐DNA

Norton et al, Obstetrics & Gynecology, 2014

1st Trimester/Integrated Screening vs cf-‐DNA: Population-‐based performance

• California prenatal screening program 2009-‐12• All singletons with either 1st or Integrated result

• Karyotypes tracked through California Chromosomal Defect Registry

Norton et al, AJOG, 2016


• cf-‐DNA detection modeled• Trisomy 13, 18, 21 and sex chromosome aneuploidy—DETECTABLE

• Mosaic, triploidy, other trisomy, translocations, other rearrangements—UNDETECTABLE

• Performance adjusted for condition-‐specific• No-‐call rate• Detection rate

• “No-‐call” as “screen positive” also modeled Norton et al, AJOG, 2016

Distribution of chromosome abnormalities

49%

13%

6%

10%

3%1%3% 15%

T21T18T13SCARare trisomyTranslocationTriploidyOther

22%1st Trimester/Integrated Screening vs cf-‐DNA:

Population-‐based performance% “No-‐Call”

DR cf-‐DNA % detected by cf-‐DNA

% detected by 1st/Int

T21 (n=1275) 3.3 99.2 95.9 92.9T18 (n=336) 10.3 96.3 86.3 93.2T13 (n=143) 12.5 91.0 79.7 80.445, X (n=161) 17.2 90.3 74.5 80.1Other SCA (n=95) 17.2 93.0 76.8 58.9Other (n=601) 4.3 0 0 53.7All (n=2575) 5.0 70.7 70.7* 81.6

Adapted from Table 2 Norton et al, AJOG, 2016*“No-‐call” results treated as normal


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% “No-‐Call”

DR cf-‐DNA % detected by cf-‐DNA

% detected by 1st/Int

T21 3.3 99.2 99.2 92.9T18 10.3 96.3 96.7 93.2T13 12.5 91.0 92.3 80.445, X 17.2 90.3 91.9 80.1Other SCA 17.2 93.0 93.7 58.9Other 4.3 0 4.3 53.7All 5.0 70.7 77.1* 81.6

Adapted from Table 3 Norton et al, AJOG, 2016*“No-‐call” results treated as Screen Positive

Impact of the “others”

• 2.6-‐3.3% of screen-‐positive women have an abnormality not detected by cf-‐DNA• Raises question of utility of using as a reflex test following abnormal conventional screening test

DON’T use cf-‐DNA as a replacement for diagnostic testing, especially in the setting of U/S abnormalities

cf-‐DNA detection: Examination in a cohort with diagnostic testing and CMA

• cf-‐DNA detection modeled• 3,140 karyotypes• 208 with karyotype changes• 173 clinical significant (83%)

• 1,037 array CGH• 100 abnormal results• 53 reflected abnormal karyotype• 47 clinically significant with normal karyotype

• TOTAL 220 clinically significant abnormalitiesShani et al, AJOG, 2016


Shani et al, AJOG, 2016

% “No-‐Call”

DR% cf-‐DNA % detected by cf-‐DNA

T21 (+mosaic) 6.9 99.2 92.4T18 6.9 96.3 89.7T13 6.9 91.0 84.745, X 17.2 90.3 74.8Other SCA 17.2 93.0 77.0Rare trisomy/ mosaic/rearrangement

0

aCGH abnormalities 0


Shani et al, AJOG, 2016

• 99 (45%) of 220 clinical significant changes undetectable with cf-‐DNA• 42% due to structural anomaly• 21% due AMA/anxiety


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DON’T order microdeletion panels as part of cf-‐DNA screening

What if cfDNA screens for “others”?• Some labs offer screening for: • Triploidy• Trisomy 16 • Trisomy 22• Trisomy 9• Vanishing twin• Specific microdeletion syndromes

• 22q, 1p36, 4p, 5p, 8q, 11q, 15q

• Genome-‐wide screening for imbalances >5-‐7 Mb

Microdeletion screeningRoutine screening by cfDNA not recommended

• Population-‐based studies unavailable• Majority do not show ultrasound findings• Are not related to maternal age• Are rare• Low PPV

Microdeletion screening PPV

MicrodeletionSyndrome

Prevalence PPV*

22q11 (DiGeorge) 1/4,000 4%1p36 1/5,000 3%5p (Cri-‐du-‐chat) 1/20,000 1%4p (Wolf-‐Hirschhorn) 1/20,000 1%15q (Angelman) 1/21,000 1%15q (Prader-‐Willi) 1/23,000 <1%

Zhao C et al, PLoSone, 2016

Does adding microdeletions help?• Common panel• 22q11• 1p36• 15q11.2-‐q13• 5p15

• Represents only 6-‐11% of clinically relevant deletions

• Reduces residual risk of significant abnormality from 1.7à1.6%

Yaron et al, Obstetrics & Gynecology, 2015

DO Provide patients with appropriate pre-test and post-test counseling


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Develop standard approach to counseling

• Pre-‐test counseling for all patients is imperative

• Can be challenging due to •Time constraints•Rapid advances •Patients’ focus on fetal sex

Important Counseling Topics

• Reasons why patients would choose to accept screening

• To help them, and healthcare providers, prepare for the birth of a child with special needs

• Because they might choose not to continue a pregnancy with a diagnosed condition

• Reasons why patients would decline screening

• They do not want this information during pregnancy and would not do anything differently

• They feel the possibility of abnormal results (whether true or false positive) would ruin the experience of pregnancy

Informed consentPatients need to know:• They can decline all screening or diagnostic testing for aneuploidy

• cfDNA is a screening test • What conditions are (and are not) being screened for• What the accuracy is re: detection rate, false positive rate

• The possibility of a “no call” result• Their options if results indicate an increased risk or are “no call”

Post-‐test counseling

• Normal results:• Should be disclosed by a medical professional designated to review this information

• “Low risk”, not “no risk”• Patients still have option to have diagnostic testing

• Abnormal results:• Ideally should be disclosed by the ordering provider

• Not diagnostic• Refer to genetic counseling or MFM specialist with expertise in this area for further evaluation

Post-test counseling


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• “No call” results:• Consider repeat testing depending on GA• Refer for genetic counseling and further evaluation

• Offer comprehensive ultrasound evaluation and diagnostic testing because of an increased risk of aneuploidy

Post-test counseling 2015 ACOG/SMFM Committee Opinion 640: Cell-‐free DNA screening for fetal aneuploidy

• Conventional screening methods remain the most appropriate choice for first-‐line screening for most women in the general obstetric population due to • Limited data on cost-‐effectiveness in low-‐risk population

• Option for any women who desires after counseling on risks, benefits and limitations

Summary

• Cf-‐DNA screening for aneuploidy can provide high detection rates and low false positive rates for common chromosome abnormalities

• Imperative to remember that these are still screening tests

• Patients need appropriate pre-‐ and post-‐test counseling

• Current cf-‐DNA screening is targeted to specific aneuploidies and does not identify 15-‐20% of karyotype abnormalities

Summary

• Microarray abnormalities may represent nearly 50% of the undetected abnormalities, or 25% of the total abnormalities, especially in the setting of an anomaly

• Following an abnormal conventional screening result, there remains a 2-‐3% residual risk of a chromosome abnormality even with a normal cf-‐DNA result

Question to ponder:

• Why are we doing prenatal screening?• To identify pregnancies at risk for a finite number of well-‐defined conditions

OR• To identify pregnancies at increased risk for any condition associated with adverse perinatal and childhood outcomes

Questions?

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