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The New Prenatal Screening Tests

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Obstetrics and Gynecology. pacificfertility.ca. Disclosure statement. I have no financial relationship with pharmaceutical or medical ultrasound ... – PowerPoint PPT presentation

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Title: The New Prenatal Screening Tests


1
The New Prenatal Screening Tests
  • St. Pauls Hospital CME Conference for Primary
    Physicians
  • November 22, 2007
  • Ken Seethram, MD, FRCSC, FACOG
  • Obstetrics and Gynecology

pacificfertility.ca
2
Disclosure statement
I have no financial relationship with
pharmaceutical or medical ultrasound corporations
associated with prenatal screening and/or
diagnosis.
3
  • ..wow, things have changed

4
Objectives
  • To make you current with 2007/08 guidelines from
    ACOG and SOCG with regards to Prenatal screening
    options
  • Help fully understand all options in order to
    better undertake counseling
  • Help understand how and when to get your patients
    screened once their options are known

5
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6
Outline
  • Definitions
  • Background and Evolution
  • Second Trimester Serum Screening
  • First Trimester Screening
  • Combined Screening
  • Guidelines
  • Final words and resources

7
Quick Definitions
  • DR Detection rate
  • the rate at which a test will pick up the
    problem. This is accuracy, not reliability
  • FPR False positive rate
  • the chance that the screening tool will be
    positive when the condition is absent
  • Screen positive
  • the literature term to describe the number of
    times the test will be positive (either truly or
    falsely)

8
Background
  • What are we screening for?
  • Aneuploidy majority of which is Trisomy 21,
    with T18, T13, and monosomy X (45X)
  • Secondary screening benefits?
  • Dating the pregnancy
  • Anatomy evaluation, placental evaluation, twins,
    early anomalies

9
Evolution of screening
  • 1887 John Langdon Down presented
  • 1930s first association made with maternal age
    and risk of major malformations
  • due to egg age, declining quality of spindle
    mechanism nondisjunction at meiosis I prior to
    fertilization aneuploidy results
  • late 1970s age was first put to use to triage
    women for amniocentesis

10
Evolution of screening
  • Age 35 became the high risk age
  • at which the rate of aneuploidy was equal to the
    rate of amniocentesis/CVS related miscarriage.
  • Therefore, maternal age was the first screening
    tool.
  • Bad news its the worst screening tool, with
    only 30-40 detection rate
  • Today dont use age 35 as a cut-off

11
1980s 2nd Trimester serum
  • AFP
  • Total hCG
  • Unconjugated estriol uE3

Inhibin A
Quad Screen (TMS/Quad multiple marker scrg
test, maternal serum screen)
12
TMS and Quad Screening
  • Nothing really has changed with multiple marker
    screening tools
  • Uses 2-4 biochemical markers to adjust the age
    related risks
  • Problem - specificity drops as disease prevalence
    increases
  • i.e. Many false positives

13
What has evolved in the first trimester? (11-14
weeks)
  • Nuchal Translucency (NT)
  • Serum biochemistry
  • Nasal Bone (NB)
  • Tricuspid regurgitation (TR)
  • Frontomaxillary facial angle (FMF Angle)

14
The First Trimester - NT
  • US measurement, 11-14w spine to skin
  • Fetal Medicine Foundation
  • Aneuploidy - a change in extracellular matrix and
    potential for cardiac/lymphatic changes causing
    increased NT
  • Congenital hearts, others

15
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16
What has evolved in the first trimester?
  • Nuchal Translucency (NT)
  • Serum biochemistry
  • Nasal Bone (NB)
  • Tricuspid regurgitation (TR)
  • Frontomaxillary facial angle (FMF Angle)

17
PAPP-A free beta hCG
  • Serum biochemistry
  • Free beta hCG (different than TMS/Quad)
  • PAPP-A (Preg Assoc. plasma protein-A)
  • relative levels are used to predict T21, T13, T18
  • Low PAPP-A
  • may be associated with a poorly developing
    placenta
  • Evolving method of screening for placental
    disease (IUGR, PIH)

18
What has evolved in the first trimester?
  • Nuchal Translucency (NT)
  • Serum biochemistry
  • Nasal Bone (NB)
  • Tricuspid regurgitation (TR)
  • Frontomaxillary facial angle (FMF Angle)

19
Nasal Bone (NB)
  • 60-70 of T21 absent Nasal bone
  • 99 of euploid fetuses have Nasal bone
  • tremendous increase in detection rates of FTS.
    High learning curve

20
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21
The First Trimester TR, FMF, Ductus Venosus
  • Tricuspid Regurge, DV, and FMF angle are somewhat
    experimental and not wide clinically used outside
    of research settings

22
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23
First Trimester Screening (FTS performance)
24
Screening Strategies
First Trimester Screening
Second Trimester Screening
  • Serum integrated
  • Integrated
  • Sequential
  • Contingency

Combined Screening
25
Screening Strategies
  • Serum Integrated Pregnancy Screening (SIPS)
  • 1st TM PAPP-A Quad (SURUSS trial, 2003)
  • Results disclosed at 17/18w
  • Integrated Pregnancy Screening (IPS)
  • 1st TM PAPP-A NT TMS/Quad
  • Same as SIPS but with NT
  • Results disclosed at 17/18w
  • SURUSS and FASTER trials 2003/2005

26
Screening Strategies
  • Sequential screening model
  • IPS but disclosed after 1st, and then 2nd TM
  • People may opt for testing after 1st TM
  • Contingency Screening models
  • FTS done - lt11000, no further testing
  • If risks gt150, CVS offered
  • If risks 150-1999 -
  • quad offered or
  • Nasal bone contingency offer NB to intermediate
    group
  • Probably best for high DRs in population based
    screening

27
Which test is best?
  • How does each model perform…

28
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29
Best performance
  • For a first trimester result
  • FTS with NT NB serum
  • Contingency screening programs
  • For a combined result
  • IPS/Contingency screening programs
  • For Late entry
  • Quad screen

30
What do the guidelines say?
  • ACOG released similar guidelines in January 2007,
    and SOGC in February
  • Basics
  • Triple screening is no longer good enough
  • Dont use age as a screening tool
  • Aim for highest DRs and lowest FPRs in any
    method
  • Consent and review all options
  • Quality assurance important in FTS programs

31
Quality Assurance?
  • Image and data audit
  • Initial certification, and on-going audit
  • FMF UK/USA
  • NTQR?
  • Importance on program based screening
  • Pre/post test counseling
  • Lab and clinical QA

32
ACOG
  • Regardless of which screening tests you decide
    to offer your patients, information about the
    detection and false-positive rates, advantages,
    disadvantages, limitations, and risks and
    benefits of diagnostic procedures, should be
    available to patients so they can make informed
    decisions.

33
SOGC
  • All women regardless of age, should be offered
    consented screening for the most significant
    aneuploidies, and a second trimester sonogram for
    dating, growth and anomalies
  • 2008 Minimum standard 75 DR, 5 FPR
  • Amnio/CVS can be offered to women over age 40,
    without screening, but screening should still be
    offered.

34
SOGC
  • The practice of using solely the previous cut-off
    of maternal age of 35 or over at the estimated
    date of delivery (EDD) to identify at-risk
    pregnancies should be abandoned

35
Whats the best test?
  • One size does not fit all
  • As long as the definitive diagnosis involves an
    invasive procedure which can cause miscarriage of
    a normal pregnancy, there is simply no substitute
    to explaining all the options, their benefits,
    and risks
  • best screen is the one which will service
    patients needs for time of results, and action
    depending on the results

36
Current Western Canada options
  • Alberta
  • Edmonton/Calgary FTS programs, provincially
    insured
  • British Columbia
  • TMS program (does not yet comply with SOGC)
  • SIPS for women over age 38
  • IPS for women over age 40
  • Private centre's for FTS with or without NB
    (complies)
  • MOH investigating new options

37
FMF Accredited FTS Centre's, BC
  • BCWH (block funding for special groups)
  • IPS (over age 40), SIPS (over age 38)
  • Prior aneuploidy, Twins
  • Pacific Ctr for Reproductive Medicine (495)
  • FTS - NT NB serum genetic counseling
  • o-s-c-a-r modeling after FMF
  • Genesis Fertility Centre (495)
  • FTS - NT serum genetic counseling

38
Resources
  • www.fetalmedicine.com
  • www.earlyriskassessment.com
  • www.mfmedicine.com
  • www.genesis-fertility.com
  • www.pacificfertility.ca
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