Prenatal Screening for Genetic Conditions The tried-and-true and the Pretty new Kathy Morris, MSSW, LCGC Senior Genetic Counselor UNM Dept OB/GYN

Learning Objectives Name 4 available prenatal screening tests for Down syndrome and Trisomy 18 Be able to state at what gestational ages each of these tests are performed Name three differences between standard biochemical screening and non-invasive aneuploidy screening Be able to order all these screening tests in Power Chart

Why screen? Most babies with birth defects and genetic conditions are born to parents with NO RISK FACTORS Prenatal screening: historically designed for a LOW RISK population

Goals of Prenatal Screening Identify fetal abnormalities that would otherwise have been missed Identify “high risk” patients who should be offered more testing High detection rate with relatively low false positive rate

Prenatal Screening Can be used in a “known risk” population to adjust risk estimates and help patients decide about further testing

Case 1 Maria Maria is a G2P1 30 year old patient who comes to initiate prenatal care at 9 weeks’ gestation. You want to offer her prenatal screening. What is it important to tell Maria about prenatal screening so she can make an informed decision? What do you want to ask Maria to help her make an informed decision about screening?

Pre-test counseling Anyone can have a baby with a birth defect, regardless of age, exposures or family history Review disorders being tested for-this screen does not test for everything Screening tests do not tell for sure if fetus is affected Positive result does not mean baby is affected, only that more testing should be considered Negative result does not guarantee that baby is unaffected

Pre-test counseling Non-invasive, no risk to baby Other (invasive) tests available to tell for sure if baby has certain conditions Screening is optional- Make sure that patient wants testing Make sure she’s having the type of test she wants (screening vs. diagnostic) Genetic counseling available for patients who require more information, recommended for those who have known risk factors

UNM Screening Options “Standard” Screening: Maternal biochemistry, with or without US Ultrasound: NT and Anatomy Non-invasive aneuploidy screening (NIPS/NIPT) Should be offered to all patients with known risk for aneuploidy as alternative to standard screen

Standard Screening: Varied protocols exist 1st trimester screen-biochemistry only 1st trimester screen-biochemistry and nuchal translucency 1st trimester screen- biochemistry, NT, nasal bone 2nd trimester serum (multiple marker screen) Combined screen: Stepwise Sequential Integrated Serum integrated Contingent Combined screens have the highest sensitivity with lowest initial positive rate

Maria Part 2 Maria says she would like prenatal screening. How would you decide which test to order?

UNM Protocol: Stepwise Sequential Screen

Current UNM Protocol: Stepwise Sequential Screen First trimester ultrasound (Nuchal Translucency) Biochemistry (PAPP-A and hCG): 11 1/2-13 6/7 weeks Risk numbers calculated If not abnormal, second serum is drawn Revised DS and T-18 risk numbers after 2nd serum

Sequential Screen Final report gives risk estimates for Down syndrome Trisomy 18 Open neural tube defects (AFP, 2nd serum only) Most effective with singleton pregnancies

Sequential Screen: Risk cutoffs FOR DS AND T-18, RISK NUMBER, not MoM values, determine positive result 1st trimester 2nd trimester Down syndrome 1/50 risk 1/270 risk Trisomy 18 1/100 risk 1/100 risk Open NTD > 2.5 MoM

Sequential Screen Detection rates After Part I After Part II Down syndrome 77% 91% Trisomy 18 80% 90% Open NTD 80% Initial positive rate 3% after 1st tri

Sequential screen in twins Lower detection rate Down syndrome: 65% (1st) and 79% (2nd) Open NTD: 58% Cannot interpret for trisomy 18 Diagnostic testing possible, but what to do if one twin is affected and the other is not?

Biochemistry 1st trimester (11 3/7-13 6/7) PAPP-A hCG 2nd Trimester (15 0/7-24 6/7 at ARUP) MSAFP Unconjugated estriol (uE3) Inhibin A

Nuchal Translucency Nuchal translucency

Increased NT-A non-specific risk factor Other chromosome abnormalities (Turner, triploidy) Heart defect Noonan Syndrome Skeletal dysplasias Diaphragmatic hernia Chest mass Many other birth defects and genetic syndromes

The bigger the NT, the higher the risk of a poor outcome Chrom. Abnorm. Fetal death Major anomalies Alive & well < 95% 0.2 % 1.3 % 1.6% 97 % 95-99% 3.7 % 2.5% 93 % 3.5-4.4 mm 21.1 % 2.7 % 10.0 % 70 % 4.5-5.4 33.3 % 3.4 % 18.5 % 50 % 5.5-6.4 50.5 % 10.1 % 24.2 % 30 % > 6.5 mm 64.5 % 19.0 % 46.2 % 15 % Souka, et al, 2005, n=96, 127 singletons

Maria Part 3 You decide, since it is the standard procedure at UNM , that you will order a stepwise sequential screen for Maria. How do you go about ordering it?

Sequential Screen Process OB provider responsible for pre-test counseling To order: Power Chart Ad hoc Women’s Imaging-OB “First trimester, NT when appropriate” Not necessary to order genetic counseling unless a risk factor or concern Ultrasound clinic orders FIRST serum screen US clinic schedules 20 week anatomy scan

Sequential Screen Process STARTING JANUARY: Screen ordered by ultrasound clinic in name of referring provider Results come to ordering provider in Power Chart inbox If abnormal, YOU contact patient, review results, refer to genetics, discuss follow-up testing options If not abnormal, referring provider orders second sequential screen

What you see in Power Chart

“AFP4 maternal screen”

EER 1st trimester

Maria Part 4 You contact Maria about her screen results and tell her “so far so good.” You go into Power Chart to order Maria’s second screen. You type in the word “second” and you see two choices: Second sequential screen and Second integrated screen. You also know that the second part of the sequential is a quad marker screen which you can order as AFP MM 4 or AFP MS 4. Which of these orders do you place for Maria?

Sequential Screen Process- 2nd serum Order “Second sequential Screen” DO NOT order a quad screen/AFP MM4 DO NOT order a second integrated screen Results come to ordering provider

Sequential Screen process Results come to ordering provider If abnormal, YOU contact patient to discuss Refer to genetics to discuss follow-up testing options

Sequential Screen: Follow-up options Positive 1st trimester screen CVS may be possible Amniocentesis Non-invasive aneuploidy screening Second trimester anatomy ultrasound

Sequential Screen: Follow-up options Positive 2nd trimester screen for DS or T-18 Amniocentesis Non-invasive aneuploidy screening Second trimester anatomy ultrasound

Positive Sequential for NTD: 2nd Trimester Elevated MSAFP-differential diagnosis NTD Ventral wall defect Rare congenital nephrosis Risk of obstetric complications

Maria Part 5 Maria’s second sequential screen shows an elevated MSAFP of 3.25 MoM. What follow-up tests would you offer to find out the explanation?

Follow-up positive screen for NTD Amniocentesis for amniotic fluid AFP Anatomy ultrasound Skull, intracranial anatomy Spine views Lower extremities: club feet Abdominal wall

Second Trimester Multiple Marker Screen

Case 2, Brittany Brittany is a 28 year old G2P1 who presents for prenatal care at 17 weeks gestation. After your thorough discussion of screening, she says she would like to screen for birth defects and genetic conditions. What test do you order? How do you order the test in Power Chart?

2nd Trimester Multiple Marker Screen If patient is too far along for 1st trimester screen Multiple marker screen can be done between 15-21 6/7 weeks Ordered by primary OB provider who does pre-test counseling Requires patient history form Run by Tricore

2nd Trimester Multiple Marker Screen Triple: MSS 3 MSAFP hCG uE3 Quad: Order as AFPMS4 of AFPMM4 Inhibin-A

2nd trimester multiple marker screen DS detection- 60-70% with triple 70-80% with quad Trisomy 18 detection- 65% with triple or quad NTD detection: 80-85% 5% screen positive rate-most are false positive

Multiple marker screen DO NOT REPEAT if positive for chromosome abnormality Possibility of having false negative repeat screen Only redraw if dating error shows too early

Negative Quad Screen

What you see in Power Chart

Brittany, Part 2 Brittany’s quad screen report is faxed to you. See next slide

Brittany, Part 3 What do you say to Brittany to explain her test results? What follow-up testing should Brittany be offered? What do you do to facilitate a more in-depth discussion of Brittany’s test results and of follow-up testing options?

Standard Screening-Advantages Most fetuses with these abnormalities would not be identified based on family history or maternal age risk factors Non-invasive-no risk to fetus Less costly than diagnostic testing, NIPT/NIPS

Standard Screening-Disadvantages False positive results lead to patient anxiety High positive rate in AMA patients Not definitive: follow-up testing needed

Ultrasound

A completely separate lecture, but… Diagnostic test for structural malformations Anatomy scan: 50% sensitivity for Down syndrome 90% sensitivity for trisomy 13 and 18 Will not identify sex chromosome aneuploidy

Non-Invasive Aneuploidy Screening (NIPS)

Non-invasive aneuploidy screening (NIPS) aka Cell-free fetal DNA screening Clinically available since 2011 DNA-based screening

NIPS Cell-free DNA fragments in maternal serum analyzed, mostly trophoblastic in origin Lab does not separate maternal from fetal DNA Can be done after 9 or 10 weeks’ gestation NOT a karyotype or microarray

NIPS Identifies more conditions than standard screening Higher detection rate than standard screening Endorsed by several professional organizations for use in patients with known risk factors for aneuploidy

NIPS Risk factors for aneuploidy Advanced maternal age (35 at EDD) Positive standard screen Malformation or soft markers on US Previously affected child or pregnancy Parental translocation carrier

NIPS Sensitivity: 99% for Down syndrome 97% for Trisomy 18 ~90% for sex chromosome abnormalities Specificity: 99% for all

NIPS Menu of tests has expanded Triploidy Several microdeletions Trisomy 9, 16 and 22 Whole genome NIPS Expensive-insurance usually covers when known risk factor Genetic counseling recommended before testing

NIPS Positive Predictive Value: Better than standard screening Depends upon sensitivity and prevalence http://www.perinatalquality.org/Vendors/NSGC/NIPT/

NIPS- Performance compared to standard screening 15,841 patients underwent standard screen and NIPS Mean maternal age 30.7 years DS Detection False + PPV NIPT 100% (38/38) 0.06% 80.9% Standard 78.9% (30/38) 5.4% 3.4% Norton, et al, NEJM 2015

NIPS- Performance compared to standard screening 1914 woman underwent standard screening and NIPS (mean age 29.6 years) Trisomy 21 NIPT Standard Sensitivity N=5 100 False + 0.3% 3.6% PPV 45.5% 4.2% Trisomy 18 N=2 0.2% 0.6% 40% 8.3% Bianchi, et al, NEJM, Feb, 2014 (Vol 370, #9, 2-27-14)

NIPS-Sources of error Placental mosaicism “Vanishing twin” Maternal aneuploidy/mosaicism (e.g sex chromosome) Maternal neoplasm

NIPS limitations Will not detect many chromosome abnormalities Limited data about performance in multiple gestations Limited data about detection of microdeletions Low fetal fraction: indeterminate or “no call” result Some data to suggest an increased risk of aneuploidy in this population

NIPS Insurance companies may or may not cover, or may not cover completely Prior authorization usually required Cost effectiveness in the low-risk population is not documented

Ordering NIPS MFM recommends NT ultrasound in conjunction if pt in 1st trimester If NT is increased, patient may opt for diagnostic test Increased NT may be an indicator of a structural malformation not associated with a chromosome abnormality Ad hoc order for genetic counseling and NT ultrasound (or for genetics if patient is >14 weeks)

Review questions Which of the following screening tests has the highest sensitivity for Down syndrome? A. Quad marker screen B. Anatomy ultrasound C. Non-invasive aneuploidy screening D. Stepwise sequential screen

Review Questions Which of the following screening tests would be most likely to likely detect trisomy 13? A. Non-invasive aneuploidy screening B. Stepwise sequential screen C. Quad marker screen D. Triple marker screen

Review questions For which condition would the positive predictive value be highest with non-invasive aneuploidy screening? A. Trisomy 13 B. Trisomy 18 C. Trisomy 21 D. Monosomy X (Turner syndrome)

Review Questions In which trimester of pregnancy can each of the following screening tests be performed? A. First sequential screen B. Second sequential screen C. Quad marker screen D. Anatomy ultrasound E. Non-invasive aneuploidy screening 1st, 2nd, 3rd

Review questions NIPS result is positive for Down syndrome. In which situation is the baby most likely to really have Down syndrome? A. A 25 year old with negative family history, normal anatomy ultrasound. B. A 40 year old with fetal AV canal on ultrasound C. A 33 year old with positive quad screen, 1 in 150 risk for Down syndrome

ACOG Committee Opinion, Sept. 2015 “…conventional screening methods remain the most appropriate choice for first-line screening for most women in the general obstetric population.” “Although any patient may choose cell-free DNA analysis as a screening strategy for common aneuploidies regardless of her risk status, the patient choosing this testing should understand the limitations and benefits of this screening paradigm…”

ACOG Committee Opinion “…a diagnostic test should be recommend for a patient who has a positive cell-free DNA test result.” “Management decisions, including termination of pregnancy, should not be based on the results of the cell-free DNA screening alone.” Women whose results are not reported, indeterminate, etc…should receive further genetic counseling and should be offered comprehensive ultrasound…and diagnostic testing…”

ACOG Committee Opinion “If a structural abnormality is identified by ultrasound, diagnostic testing should be offered rather than cell-free DNA screening.” “Cell-free DNA screening is not recommended for women with multiple gestations” “Routine cell-free DNA screening for microdeletion syndromes should not be performed.”

Questions?