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Prenatal Risk Profiles

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

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  1. Prenatal Risk Profiles Joseph Breuner, MD 5/6/03

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

  3. Objectives • 1. Understand the testing strategy • 2. Counsel your patients right the first time • 3. Understand the results

  4. Understand the testing strategy • Definitive diagnostic tests for down syndrome exist, but they’re expensive and can cause harm.

  5. Understand the testing strategy: amniocentesis

  6. 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.

  7. Understand the testing strategy: chorionic villus sampling

  8. 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

  9. Understand the testing strategy • A screening test is necessary to sort out who will benefit from amnio or cvs • 3 screening strategies are available

  10. Understand the testing strategy • 1. Age related-- • 2. triple or quad screen • 3. Integrated screen

  11. Understand the strategy • All 3 strategies use a cutoff near 1/200 to offer amnio

  12. 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

  13. 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.

  14. 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%

  15. Understand the strategy: triple screen • U.S. Preventive Services Task Force (USPSTF) recommends triple analyte screening for all pregnant women.

  16. Understand the strategy: triple screen • Miscarriages From Amniocenteses perCase of Down Syndrome Detected • 0.25-0.45

  17. Understand the strategy: triple screen • Cost per Case of DownSyndrome Detected$22,000-45,000

  18. 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

  19. 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

  20. Understand the strategy-costdynacare 4/02 • Triple screen 130 • 1st trimester only 150 • Quad screen 170 • Combined (no US) 265 • Integrated 415

  21. 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.

  22. 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

  23. 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

  24. Counsel your patients right the first time-1st element Down • 1. Describe Down syndrome • Down syndrome is a genetic cause of mental retardation.

  25. 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

  26. 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%).

  27. 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.

  28. 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.

  29. Counsel your patients right the first time-5th-Incite a decision • Ask the patient what they would like to do.

  30. 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

  31. Counsel your patients right the first time • 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

  32. Counsel your patients right the first time • 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?’

  33. Understand the results: down syndrome • 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

  34. Understand the results: down syndrome • 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

  35. Understand the results: down syndrome • Check these before calling patient • Incorrect gestational age? • Weight correct? • Race correct? • No multiple gestation or IDDM?

  36. Understand the results: down syndrome • 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

  37. Understand the results: down syndrome • 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

  38. Understand the results: NTD • high AFP. • Consider neural tube defect. • Dx confirmed with amniotic fluid AFP (also high) and 2nd trimester anatomic survey ultrasound showing defect.

  39. Understand the results: low AFP syndrome • 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

  40. Understand the results:amnio • What is a karyotype? • How is it reported? • What other trisomies can be reported? • Any other results possibilities?

  41. Understand the results--karyotype

  42. Understand the results: other trisomies • Trisomy 18 • incidence 1/5000 • 20 - 30% die in the first month 90% die by age oneTrisomy - 95%Translocation - 2%Mosaic - 3%

  43. Understand the results: other trisomies • Trisomy 13 • incidence 1/5000 • Congenital hearts - 80%Dextrocardia - (reversed) - 20-50%Omphalocele - 10%Holoprosencephaly - 66%(early brain defect)

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

  45. Objectives • 1. Understand the testing strategy • PRP is a screening test which will benefit some patients

  46. Objectives • 2. Counsel your patients right the first time DALAI • give yourself 10 minutes • do it < or at 12 weeks • include 5 elements

  47. Objectives • 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

  48. Thank you!

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