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Early Risk Assessment Program: Performance Update 2008. Photo: courtesy Travel Alberta. Screening for Fetal Aneuploidy 11-13+6 weeks. Objectives:. The provision of information for individuals. 32 nd RCOG Study Group.

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Early Risk Assessment Program:

Performance Update 2008

Photo: courtesy Travel Alberta


Screening for Fetal Aneuploidy 11-13+6 weeks


  • The provision of information for individuals

32nd RCOG Study Group

  • Women have the right to access information about the health of their fetus

SOGC Statement on Access to Genetic Screening

January 2007



J Obstet Gynaecol Can 2007;29 (2):146-161

1. All pregnant women in Canada, regardless of age, should be offered through an informed consent process, a prenatal screening test for the most common clinically significant fetal aneuploidies in addition to a second trimester ultrasound for dating, growth and anomalies. (I-A)



2. Maternal age screening is a poor minimum standard for prenatal screening for aneuploidy and should be removed as an indication for invasive testing. Amniocentesis/chorionic villi sampling (CVS) should not be provided without multiple marker screening results except for women over the age of 40. Patients should be counseled accordingly. (I-A)


3. In 2007, as a minimum standard, any prenatal screen offered to Canadian women should have a 75% detection rate with no more than a 5% false positive rate (3% by 2008) for Down syndrome. The performance should be substantiated by annual audit. (III-B).

Wald et al. 2003; Nicolaides et al. 2005


11. By 2008, screening programs should aim to provide a screen that, as a minimum, offers women who present in the first trimester a detection rate of 75% for Down syndrome, with no more than a 3% false positive rate. (III-B)


4. First trimester nuchal translucency should be interpreted for risk assessment only when performed by sonographers/sonologists trained and accredited to provide this service and with ongoing quality assurance.(II-2A)

It should not be offered as a screen without biochemical markers except in the context of multiple gestation pregnancies (I-A).


Principles of Screening

Characteristics of Screening Test

Sensitivity (Detection rate): Abn screen, abn result

False Positive Rate*: Abn screen, normal result

False Negative Rate: Normal screen, abn result

Specificity: Normal screen, normal result = 100-FPR

Likelihood Ratio: Proportn Abn / Proportn Normal

* Also called initial positive rate, is used interchangeably with amniocentesis rate


Background risk

Adjusted risk =


Background- (a priori) risk

Nuchal Translucency



LR of screening test



Adjusted risk = a priori risk x LR1 x LR2 x LR3…

New Marker

Screening for trisomy 21


Prenatal Screening in Alberta

  • Maternal age alone
  • MSS 1990’s
    • Not a funded program, no audit or follow-up

In Calgary

  • Nuchal translucency screening* 2002
    • No MSS after NT, unless with genetic counseling
    • 18-20 week scan

Nuchal Translucency Screening*


Maternal Serum Screen (MSS)


Detailed Anatomy

Genetic Sonogram*

Pregnancy Outcome



11-14 15-17 18-20

*Southern Alberta Center for

Maternal Fetal Medicine (MFM Centre)


Prenatal Screening in Calgary

Nuchal Translucency Screening Clinic* (2002-March 2006)

  • Pre- and post-NT counselling
  • 18 “NT certified” technologists
  • # of patients given NT-adjusted risk n= 9,971
  • DR 75%, FPR 9 % at 1/300 (mid-TM risk)
  • 32% ≥ 35 years of age



*Southern Alberta Center for

Maternal Fetal Medicine (MFM Centre)


Screening for Trisomy 21

Fetal NT + maternal free ß-hCG & PAPP-A (FTS)

  • The best marker is NT
  • Inclusion of ß-hCG and PAPP-A improves DR by 15-20%
  • Five prospective studies of FTS (n=76,977), DR of Tr21 362/409 (89% for 5% FPR)

The Early Risk Assessment (ERA) Program:

First Trimester Screening and

Early Detection of Pregnancy Complications


“To promote the health and well-being of pregnant women through a collaborative and multidisciplinary prenatal risk assessment program that would enable early, more accurate identification and management of pregnancies at increased risk for adverse perinatal health outcomes”.


Early Risk Assessment Program : Prenatal Screening for Chromosome Disorders

First Trimester Combined Screening

  • Purpose:
  • To introduce FTS (OSCAR model)
  • To develop patient and physician educational materials
  • To evaluate program performance and patient satisfaction
  • Maternal age
  • NT
  • Free-bHCG
  • PAPP-A

Early Risk Assessment Program: Earlydetection ofPregnancies at risk of Adverse Outcome

1. To examine the predictive value certain biochemical/US markers (11 -20 w) in detection of women at increased risk of poor pregnancy outcome (pre-eclampsia, IUGR, preterm labor),

2. To identify risk factors and interventions that may improve pregnancy outcome in this group





10 12 14 16 18

why point of care
Why “Point of Care?”

One Stop Clinics

  • One stop clinics have developed in several clinical areas
    • breast cancer screening, menopausal clinics, oncology assessment, cardiovascular risk clinics, one-stop surgical clinics
  • Benefits:
    • integration of clinical and diagnostic services
    • better use of clinical time, improved diagnostic efficiency
oscar one stop clinic assessment of risk
OSCAR: “One-Stop Clinic Assessment of Risk”
  • Patient advantages:
    • Maximizes patient satisfaction
    • Reduced number of patient visits
    • Decreased patient travel costs, (missing work, babysitting, parking), anxiety, and stress especially that associated with waiting for results
    • Allows for timely, qualified interpretation of results

Evidence and Innovations leading to OSCAR

  • Ultrasound markers of chromosomal anomalies - fetal nuchal translucency thickness at 11-14 weeks.
  • Maternal serum Biochemical markers of chromosomal anomalies - free b-hCG & PAPP-A at 10-14 weeks.
  • Development of new rapid assay technology for biochemical marker measurement leading to Point of Care testing.
oscar in calgary
OSCAR in Calgary*

One Stop Clinic for Assessment of RiskSouthern Alberta Centre for MFM

(NT clinic + Astraia) + (DELFIAXpress + Lifecycle) = OSCAR

Woman arrives

Woman departs

Post-test counselling

Pre-test counselling*

Free b HCG



Blood sample

Risk Assessment


Examination (11-13+6 weeks scan)

U/S data

* Mean T/O time 92 minutes

*1-1 Counselling, video, pamphlets

Invasive testing usually not same day

oscar in calgary1
OSCAR in Calgary

FTS Uptake March 2006-2007

non oscar in calgary 2 step model
Non-OSCAR in Calgary(2-Step Model)

Woman arrives

“-ve screen”

Report mailed

“+ve screen”

Nurse/ counsellor calls,

appointment arranged

Step 1

  • Demographics reviewed
  • Counselling as needed
  • Consent signed

Risk Assessment

Same day report

NT Ultrasound


2 MFM sites

Woman departs

Blood sample


OSCAR facility

U/S data

*Own MD, website, pamphlets

Step 2

first trimester serum screening detection
First Trimester Serum Screening Detection

1/250 Risk cut-off

Biochemistry Works Better Earlier

Spencer et. Al Ann. Clin. Biochem. 2003; 40: 219-231

non oscar

One Stop Clinic for Assessment of RiskSouthern Alberta Centre for MFM

Woman departs

Woman referred for FTS

Directed to educational materials*

Post-test counselling

Free b HCG


NT Scan

Blood sample at any CLS facility

starting at 9 weeks gestation

Risk Assessment

NT Ultrasound

At Beddington or Southport EFW MFM Clinics

Free b HCG


mean maternal age
Mean Maternal Age

(* 18% in the CHR ≥ 35 years)

fts performance
FTS Performance

March 13 2007- March 13 2008

Total number screened 6984

Initial positive rate (or False Positive rate):T21

fts performance1
FTS Performance

March 13 2007- March 13 2008

  • Screening for Trisomy 21
  • DR Trisomy 21 93% (29/32), FPR 6.5% (1/300)
  • 2 “false negative” cases:
    • 1 negative screen for T21, +ve T13,18 (had invasive)
    • Other case: no blood obtained, NTS alone.
  • Characteristics of the T21 cases
  • 27/ 31 Trisomy 21 (87%) detected prenatally
      • CVS 17/27 (63%), amnio10/26 (38.4%)
    • 3 LB T21 in screen +ve group (declined invasive)
    • 1 had no invasive (FN result)
      • Risk assessment on NT alone due to unsuccessful phlebotomy
fts performance2
FTS Performance

March 13 2007- March 13 2008

  • Invasive testing in FTS screened patients
  • Overall invasive rate: 292/6983 = 4.1 %
  • Invasive rate among screen +ve patients: 229/439 = 52%
    • Average risk of screen positive patients who had invasive testing 1:90
    • Average age 34 years, 53% over 35,13% over 39
    • Average risk of screen positive patients who did not have invasive testing 1:151
    • Average age 34 years, 53% over 35, 20% over 39
fts in calgary 2006 7
FTS in Calgary 2006-7

Characteristics of the true +ve (T21) screens (n=20)

Mean GA 60 mm

Mean T21 risk: 1:22

Mean NT: 3.6 (range 1-8.2 mm)

Average age 36.3 years (range 22-45, 68% over 35 years)

Average fβ-HCG 2.5 MOM (range 0.7-4.24)

Average PAPP-A 0.5 MOM (range 0.12-0.95)

OAPR: 1:16

fts in calgary 2007 8
FTS in Calgary 2007-8

Characteristics of the true +ve (T21) screens (n=29)

Mean GA 66 mm

Mean T21 risk: 1:43

Mean NT: 3.9

Average age 36.7 years (range 22-45)

Average fβ-HCG 2.5 MOM (range 0.5-6.0)

Average PAPP-A 0.6 MOM (range 0.1-2.1)

OAPR: 1:15

fts in calgary 2006 8
FTS in Calgary 2006-8

Characteristics of the Trisomy 21 cases (n=23)

  • Average age 36.5
  • Average risk in true positives: 42
    • 26/49 (53%) had 1:2,
    • 37/49 (77%) 1:10 or higher.
    • 44/49 (89%)1:150 or higher
fts program in calgary
FTS Program in Calgary
  • Key Points
  • One-stop multidisciplinary approach associated with high patient satisfaction
  • Operationally efficient (few call backs, demographic and ultrasound information available, collaborative atmosphere between disciplines (MFM, genetics, ultrasound, lab, nursing).
  • Established infrastructure for efficient high quality ultrasound as well as audit and research (linked to Alberta Perinatal Health database)
  • Ability to introduce new markers/ protocols
  • Performance excellent and within expected range
province of alberta proposed program
Province of Alberta: Proposed Program
  • For women presenting for prenatal care before 13 weeks and 6 days of pregnancy, there would be two options:
    • Where Nuchal Translucency available:
      • First trimester Combined Screening (FTS, GOLD STANDARD)
    • Where Nuchal Translucency not available:
      • Early Contingent Screening
      • Combines maternal age with blood test (biochemical markers: PAPP-A and free beta HCG )
      • If risk assessment is above the predetermined risk cut-off, a nuchal translucency ultrasound would be recommended (estimate10- 20% of population).
  • For women presenting for prenatal care after 14 weeks and before 19 weeks and 6 days:
    • Second trimester Quad Maternal Serum Screening
Community-based screening for Down’s Syndrome in the first trimester using ultrasound and maternal serum biochemistry
  • 2 year pilot study in Western Australia, a geographically isolated state with an annual birth rate of 25,000.
  • Outcomes linked to State wide birth and anomaly information systems.
  • FTS is largely community based with women accessing a variety of independent ultrasound practices and local collection centres served by one central laboratory with distances in some instances over 1000 Km away.

Narelle Hadlow et al, BJOG 2005:112; 1561-1564

Community-based screening for Down’s Syndrome in the first trimester using ultrasound and maternal serum biochemistry
  • In the study period NT was only concentrated in the Perth Metro area.
  • Women had blood collected at their local collection centre in their rural community (over 100 sites). Separated, frozen and sent by air or land transport in frozen state.
  • Women travelled to Perth for NT, biochemistry result available on day of scan in 96% of cases, and after the NT in 4% of cases.
  • Study screened over 10,000 women and detection rate was 90.6% with a false positive rate of 3.6% (Mean age 30.7 )
  • All sonographers/obstetricians FMF approved and either trained in London or via the FMF delegated RANZCOG program

Narelle Hadlow et al, BJOG 2005:112; 1561-1564

delivery of screening
Delivery of Screening
  • Multidisciplinary !!
  • Numerous stakeholders:
    • Pregnant women, MFM, obstetrics, family medicine, midwives, radiology, sonography, lab services, genetics, pathology………
  • Direction of flow

Ultrasound Biochemistry

oscar in calgary2
OSCAR in Calgary

Number of abnormal cytogenetic results n= 39 (Ascertainment: electronic linkage with Alberta perinatal health database and cytogenetic lab; outcome not complete)

+ve screen

-ve screen

Total detected prenatally 37/39 (95%)


Uterine Arteries

NB, TC, DV, FMF Angle

Placental hormones

Anatomic Survey

11-13 weeks 6 days scan


Nuchal Screening

The First Trimester Scan (11-13 weeks 6 days)

biochemical screening centralized vs poc
Biochemical Screening: Centralized vs POC

Centralized laboratory services

  • Minimizes costs
  • High standards
  • Can serve locally, regionally, nationally
  • “Point of Care”
    • Not as common in non-private HC systems
    • Costs offset by operational efficiency, consolidation of services, fewer patient visits, better care

Prospective 1st Trimester Screeningsingleton pregnancies over a 5 year period

NT alone would have picked up 70% of cases at a 5% FPR,

Biochemistry alone would have picked up 70% at a 5% FPR

but combined a further 22% are identified



Satisfaction with OSCAR program

These results were independent of maternal age, parity, education and screen result, except women with lower education levels were significantly more likely to be satisfied with pre-test counseling than women with higher education levels (p=0.0071)

satisfaction with overall service by service delivery model
Satisfaction with Overall Serviceby Service Delivery Model
  • Although satisfaction with overall service was high for both the one-stop and two-stop service delivery models, women who had the one-stop service were more likely to be satisfied than women who had the two-stop service (p<0.0001).

Missing Responses: 135

oscar satisfaction study
OSCAR Satisfaction Study
  • Uptake of invasive testing in women attending the OSCAR clinic:
    • Positive screen (T21): 49.1%
    • Negative screen: 2.7%
  • Invasive uptake related to level of risk

1/100 1/100-1/1000 >1/1000

*DR of T21 87% at 5% FPR


Early Prenatal Risk Assessment:

More Than an Aneuploidy Screen



Fetal anatomy

UA Doppler

Placental morphology

1st TM Volume (3D)

Maternal Serum


Free beta hCG

Store sample


Fetal echo

Uterine artery Doppler

Placental morphology

Timing of scan

Maternal Serum



Contingent screening

Store sample

TV cervix clinic

U/A Doppler

Cervical length

(c/w 18-20 week)

11-14 15-17 18-20 22-24


PHASE 2: Pregnancy complications




1.) To evaluate women’s satisfaction with first trimester combined screening (FTS),

2.) To compare delivery models (one-stop (OSCAR*) versus 2-stop screening).

*March 13, 2006- March 13, 2007

# Women screened n= 5013

# Completed surveys n= 3763 (75%)

Eligible OSCAR patientsn=2670/3763 (71%)

  • The Calgary FTS OSCAR model meets women’s expectations, is associated with a high degree of satisfaction and was preferred over the 2-stop model
  • Receiving results early in pregnancy and same day is important
  • A high proportion of women were reassured by their results regardless of whether they were screen negative or positive.
  • Uptake of invasive prenatal diagnosis among screen positive patients correlated with level of risk
conclusions cont d
  • These results may imply that
    • Women favor individualized risk assessment versus being categorized as screen negative or positive
    • Immediate access to 1-1 post-test counseling with a health professional, as in the OSCAR model, has important impact on perception of test results
    • Further research to evaluate this is under consideration
  • The 2 stop model has been revised …