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Prenatal Risk Profiles. Joseph Breuner, MD 5/6/03. Goal. Competence in screening your prenatal patients for down syndrome (DS). Objectives. 1. Understand the testing strategy 2. Counsel your patients right the first time 3. Understand the results. Understand the testing strategy.

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Prenatal risk profiles

Prenatal Risk Profiles

Joseph Breuner, MD

5/6/03


Prenatal risk profiles
Goal

  • Competence in screening your prenatal patients for down syndrome (DS)


Objectives
Objectives

  • 1. Understand the testing strategy

  • 2. Counsel your patients right the first time

  • 3. Understand the results


Understand the testing strategy
Understand the testing strategy

  • Definitive diagnostic tests for down syndrome exist, but they’re expensive and can cause harm.



Understand the testing strategy amniocentesis1
Understand the testing strategy: amniocentesis

  • Purpose:karyotype and amniotic fluid AFP.

  • Gestational age 14 wks to term

  • Miscarriage rate 1/200 to 1/500,

  • results take 10-21 days depends on lab

  • useful for down, cystic fibrosis, tay-sachs, neural tube defect.



Understand the testing strategy chorionic villus sampling1
Understand the testing strategy:chorionic villus sampling

  • Obtains chorionic villi from the placenta

  • Gestational age 10-12 wks

  • higher miscarriage rate--1-1.5%

  • results are chromosomes, no amniotic fluid AFP. Takes about 10 d.

  • Useful for down syndrome, cystic fibrosis, tay-sachs


Understand the testing strategy1
Understand the testing strategy

  • A screening test is necessary to sort out who will benefit from amnio or cvs

  • 3 screening strategies are available


Understand the testing strategy2
Understand the testing strategy

  • 1. Age related--

  • 2. triple or quad screen

  • 3. Integrated screen


Understand the strategy
Understand the strategy

  • All 3 strategies use a cutoff near 1/200 to offer amnio


Understand the strategy age related risk
Understand the strategy: age-related risk

  • Age-related risk is 1/1700 at age 20, 1/400 at age 35 and 1/30 at age 45.

  • Beginning in 1987, amnio was offered to all women over age 35

  • this strategy misses 65% of down syndrome cases

  • PPV 0.5%, FP=% women over 35


Understand the strategy triple screen
Understand the strategy: triple screen

  • Triple or quad screen uses HCG, estradiol, alpha-fetoprotein (afp) +/- inhibin drawn between 15-21 weeks

  • Invalid for twins and diabetic

  • Predicts down’s risk using ‘multiples of the median’ (MOM) of analytes and age-related risk.


Understand the strategy triple screen1
Understand the strategy: triple screen

  • With positive test defined at 1/200, triple detects 65% of cases, quad detects 80% of cases.

  • PPV=.5%, FP rate =5%


Understand the strategy triple screen2
Understand the strategy: triple screen

  • U.S. Preventive Services Task Force (USPSTF) recommends triple analyte screening for all pregnant women.


Understand the strategy triple screen3
Understand the strategy: triple screen

  • Miscarriages From Amniocenteses perCase of Down Syndrome Detected

  • 0.25-0.45


Understand the strategy triple screen4
Understand the strategy: triple screen

  • Cost per Case of DownSyndrome Detected$22,000-45,000


Understand the strategy integrated screen
Understand the strategy: integrated screen

  • Combine 3 separate measurements

  • 1. Serum PAPP-A and free estradiol at 8-12 weeks

  • 2. Nuchal translucency at 10-13 weeks, requires certified US tech.

  • 3. Quad screen at 15-20 weeks.

  • Risk reported as a single ratio after quad screen


Understand the strategy integrated screen1
Understand the strategy: integrated screen

  • Will diagnose 90-95% of down syndrome cases with same false positive rate 5%.

  • Logistics and Cost issues a problem


Understand the strategy cost dynacare 4 02
Understand the strategy-costdynacare 4/02

  • Triple screen 130

  • 1st trimester only 150

  • Quad screen 170

  • Combined (no US) 265

  • Integrated 415


Counsel your patients right the first time intro
Counsel your patients right the first time-intro

  • Tips: good to check prenatal risk questionnaire now if you didn’t do so at first visit---family history of any birth defects, CF, Tay-sachs?

  • Patients will miss much of what you tell them. Be open to questions as you go.

  • Timing: ideal is 12 weeks, so they can think about it prior to visit.


Counsel your patients right the first time the setup
Counsel your patients right the first time--the setup

  • Tell the patient you’re going to help them decide whether to get a blood test available to them


Counsel your patients right the first time 5 elements
Counsel your patients right the first time-5 elements

  • 1. Describe Down syndrome

  • 2. Describe Age-related risk

  • 3. Describe Limitations of testing

  • 4. Describe Amniocentesis

  • 5. Incite a decision.

  • The dalai lama is a pretty good counselor, if you like acronyms


Counsel your patients right the first time 1st element down
Counsel your patients right the first time-1st element Down

  • 1. Describe Down syndrome

  • Down syndrome is a genetic cause of mental retardation.


Counsel your patients right the first time 2nd element age
Counsel your patients right the first time-2nd element-Age

  • 2. Describe Age-related risk

  • Convey a sense of patient’s age related risk.

    • all 9/10000 1/1111 1/1100

    • 20 6/10000 1/1666 1/1700

    • 30 11/10000 1/909 1/900

    • 35 26.5/10000 1/377 1/400

    • 45 330/10000 1/30 1/30


Counsel your patients right the first time 3rd limitations
Counsel your patients right the first time-3rd -Limitations

  • Describe Limitations of testing

  • This is not a perfect test. The test identifies only some of the babies with Down syndrome (65-80%) and there is a small risk of a false positive test (5%). The test is good at ruling out Down syndrome (negative predictive value 99.5%).


Counsel your patients right the first time 4th amniocentesis
Counsel your patients right the first time--4th-Amniocentesis

  • 4. Describe Amniocentesis

  • the blood test is not diagnostic. If your blood test is positive, I’ll ask you to see a counselor to talk about amniocentesis.


Counsel your patients right the first time 4th amniocentesis1
Counsel your patients right the first time--4th-Amniocentesis

  • A needle will go through your abdomen and draw off some fluid around the baby. There is a small chance of miscarriage(1/200-1/500) from the procedure.


Counsel your patients right the first time 5th incite a decision
Counsel your patients right the first time-5th-Incite a decision

  • Ask the patient what they would like to do.


Counsel your patients right the first time 5 elements1
Counsel your patients right the first time-5 elements decision

  • 1. Describe Down syndrome

  • 2. Describe Age-related risk

  • 3. Describe Limitations of testing

  • 4. Describe Amniocentesis

  • 5. Incite a decision.

  • The dalai lama is a pretty good counselor, if you like acronyms


Counsel your patients right the first time
Counsel your patients right the first time decision

  • takes an average of 10 minutes.

  • discuss abortion if the patient asks about it.

  • I also avoid NTD, ‘low AFP’, which you’ll test for, and CF, tay-sachs which you don’t


Counsel your patients right the first time1
Counsel your patients right the first time decision

  • Try this out in pairs. Use the handout as a reference if necessary, DON’T READ IT

  • The patient in the dyad should be a little difficult--don’t get some things, ask questions about something from 2 minutes ago. ‘are you trying to make me get an abortion?’


Understand the results down syndrome
Understand the results: down syndrome decision

  • Your triple or quad screen result will come back in 3-5 days.

  • Each analyte will be reported as a multiple of the median,

  • patient’s down syndrome risk is more likely with: AFP low, estradiol low, HCG high, inhibin high

  • Overall DS risk reported as a fraction


Understand the results down syndrome1
Understand the results: down syndrome decision

  • Things to think about before you call your patient:

  • Think of results as positive (>1/200) and negative(<1/200). This is simpler for patients and works better


Understand the results down syndrome2
Understand the results: down syndrome decision

  • Check these before calling patient

  • Incorrect gestational age?

  • Weight correct?

  • Race correct?

  • No multiple gestation or IDDM?


Understand the results down syndrome3
Understand the results: down syndrome decision

  • Positive results obligate you to call the patient. Don’t ask your nurse to do this

  • Document the call.

  • positive result = an increased risk of down syndrome.

  • I suggest they see the genetics counselors to discuss whether or not to have amnio


Understand the results down syndrome4
Understand the results: down syndrome decision

  • Timing: 3-7 d to see genetics counselor, 5-7 d to schedule amnio, 10-18 d for amnio results

  • terminations in washington state to 24 weeks, either here at swedish through perinatal or at cedar river

  • genetics counselors can access info for patients on down syndrome resources


Understand the results ntd
Understand the results: NTD decision

  • high AFP.

  • Consider neural tube defect.

  • Dx confirmed with amniotic fluid AFP (also high) and 2nd trimester anatomic survey ultrasound showing defect.


Understand the results low afp syndrome
Understand the results: low AFP syndrome decision

  • Patients with low AFP have in increased risk of oligohydramnios, fetal distress, PIH, and stillbirth

  • standard of care is to monitor at 32 wks with weekly NST and NST/AFI at 36 wks

  • Unsupported by evidence


Understand the results amnio
Understand the results:amnio decision

  • What is a karyotype?

  • How is it reported?

  • What other trisomies can be reported?

  • Any other results possibilities?



Understand the results other trisomies
Understand the results: other trisomies decision

  • Trisomy 18

  • incidence 1/5000

  • 20 - 30% die in the first month 90% die by age oneTrisomy - 95%Translocation - 2%Mosaic - 3%


Understand the results other trisomies1
Understand the results: other trisomies decision

  • Trisomy 13

  • incidence 1/5000

  • Congenital hearts - 80%Dextrocardia - (reversed) - 20-50%Omphalocele - 10%Holoprosencephaly - 66%(early brain defect)


Prenatal risk profiles
Goal decision

  • Competence in screening your prenatal patients for trisomies and neural tube defects


Objectives1
Objectives decision

  • 1. Understand the testing strategy

  • PRP is a screening test which will benefit some patients


Objectives2
Objectives decision

  • 2. Counsel your patients right the first time DALAI

  • give yourself 10 minutes

  • do it < or at 12 weeks

  • include 5 elements


Objectives3
Objectives decision

  • 3. Understand the results

  • Dating and other factors affect lab interpretation

  • consider results + or - for DS

  • encourage pts to see genetics counselor

  • DS, NTD, ‘low AFP’ syndrome


Thank you
Thank you! decision