Screening “the systematic application of a test procedure to identify individuals at sufficient risk to warrant diagnostic investigations” CVS 12wks Amniocentesis

Screening

“the systematic application of a test procedure to identify individuals at sufficient risk to warrant diagnostic

investigations”

• CVS 12wks

•Amniocentesis 16wks

•Morphology Ultrasound 18wks

Aim is to maximise detection of affected pregnancies and minimise false +ves

Biochemical Markers;2nd Trimester 1st TrimesterAFP free hCG free hCGuE3 Papp-A

Inhibin A

Other Markers; Nuchal Translucency

Maternal age Gestational age

Screening for trisomy 21Screening for trisomy 21

Marker Levels Change Significantly with Gestation

Measured levels are converted to Multiples Of the Population Median or MoM values.

Reference is therefore 1 MoM

beta hCG at 10 wks GA

Patient 120 IU/L = 2 multiples Median 60 IU/L

MoMs are independent of gestational age and concentration Units

LogMoM values are used in calculations as they exhibit a Gaussian distribution ( Mean +/- SD)

Maternal age Maternal age

Background RiskBackground Risk

0.0001

0.001

0.01

0.1

1

10

20 25 30 35 40 44

Years

Risk %

Trisomy 21Trisomy 21



xxx/xxy/xyyxxx/xxy/xyy

45x45x

TriploidyTriploidy

Snijders et al 1995Snijders et al 1995 Nicolaides et al., The 11-14-week scan, London 1999

Snijders et al 1995Snijders et al 1995

65% Trisomy 2165% Trisomy 21

00

2020

4040

6060

8080

100100

1010 1515 2020 2525 3030 3535 4040



<1% Triploidy<1% Triploidy

95% 47xxx/xxy/xyy95% 47xxx/xxy/xyy

20% 45x20% 45x

%%

Gestational age Gestational age

Background RiskBackground Risk

Nicolaides et al., The 11-14-week scan, London 1999

Assessment of RiskAssessment of Risk

Previous Chromosomal AbnormalityPrevious Chromosomal Abnormality

}}45XO45XO47XXY/XXX47XXY/XXXTriploidyTriploidy

Trisomy 21 Trisomy 21 Trisomy 18Trisomy 18Trisomy 13Trisomy 13 }} ++

0.50 - 0.75%0.50 - 0.75%

100100,,000 pregnancies000 pregnancies

Maternal age Maternal age 606030%30%

Serum biochemistry at 16 wksSerum biochemistry at 16 wks 13013065%65%

Nuchal translucency (NT) at 12 wksNuchal translucency (NT) at 12 wks 75%75% 150150

Fetal NT & ß-hCGFetal NT & ß-hCG & PAPP- A at 12 wks & PAPP- A at 12 wks 18018090%90%

Screening for trisomy 21Screening for trisomy 21

Effectiveness of different methods of screeningEffectiveness of different methods of screening

Method of screeningMethod of screening Number detectedNumber detectedDetection rateDetection rate

Screen positive 5%Screen positive 5%N=5,000N=5,000

Trisomy 21Trisomy 21N=200N=200

Nicolaides KH. Fetal nuchal translucency. Am J Obstet Gynecol 2004Nicolaides KH. Fetal nuchal translucency. Am J Obstet Gynecol 2004

SAMSAS©

Maternal Age Maternal Age Screening aloneScreening alone

Second trimester Second trimester biochemical biochemical

screeningscreening

First trimester First trimester combined combined screeningscreening

Amniocenteses Amniocenteses performed per performed per case detectedcase detected

250250 4400 2020

Fetal loss per case Fetal loss per case of Down of Down

syndrome syndrome detecteddetected

1 : 11 : 1 1 : 1 : 55 1 : 1 : 1010

SAMSAS©

1st trimester Risk Odds show better separation between Unaffected and Affected pregnancies when compared to 2nd trimester Risk Odds.

Risk Odds 1st Trimester vs 2nd Trimester

0

0.05

0.1

0.15

0.2

0.25

0.3

-14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0

- Log Risk Odds

Unaffected 1st

Affected 1st

Unaffected 2nd

Affected 2nd

Age Specific Performance Comparison of 1st and 2nd Trimester Screening.

Maternal Age vs Recall and Detection

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

100.0

15 20 25 30 35 40 45

Maternal Age at Delivery

%

%RR 2nd %DR 2nd %RR 1st %DR 1st

RR

DR

SAMSAS©

DS Risk = Mat. Age Risk x LR

Discriminatory Variable

3210-1-2

1.0

.8

.6

.4

.2

0.0

Unaffected Affected

Detection Rate

False -veFalse +ve’s

h1

h2

LRaff = h2/h1Y= 0.425*ln_beta_MoM – 0.631*ln_Papp-a_MoM +0.761*ln_NT_MoM

SAMSAS©

DS Risk =Mat. Age Risk × LR

• 20 yrs = 1 in 1600 × 2 = 1 in 800

• 30 yrs = 1 in 1100 × 2 = 1 in 550

• 35 yrs = 1 in 500 × 2 = 1 in 250

• 40 yrs = 1 in 156 × 2 = 1 in 78

• 45 yrs = 1 in 40 × 2 = 1 in 20

SAMSAS©Beta MoM's vs Weight Kg

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

40 50 60 70 80 90 100 110 120

Kgs

Mo

M

Pappa MoM's vs Weight Kg

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

40 50 60 70 80 90 100 110 120

KgsM

oM

Noveux 1996, Graaf/Cuckle 2000, SAMSAS/Murdoch 2002

490490490N =

Unaffected 1st Trimester

PAPP_A_MoMBHCG_MOMNT_MOM

3

2

1

0

SAMSAS©

196196196N =

Twins 1st Trimester


Mo

M

5

4

3

2

1

0

FMF software uses data as published by Spencer, Br J Obstet Gynaecol March 2003, Vol. 110, pp. 276-280. Median MoMs free B-hCG = 2.15 and Papp-A = 1.93 weight corrected.

Increasing Incidence of Twins

(1990–2003) 1:70 to 1:55

* Assisted reproduction

* Rate of twinning increases with age.

>17% of pregnancies are now to women 35yrs or over, up from <9% in 1990.

0

2

4

6

8

10

12

14

16

18

20

-3.5 -2.5 -1.5 -0.5 0.5 1.5 2.5 3.5

Free ßhCG (SD)

% Trisomy 21Normal

20

0

2

4

6

8

10

12

14

16

18

-3.5 -2.5 -1.5 -0.5 0.5 1.5 2.5

PAPP-A (SD)

% NormalTrisomy 21

Biochemistry and Screening for trisomy 21Biochemistry and Screening for trisomy 21

• In trisomy 21 pregnancies at 11-14 weeks, maternal serum free ß-hCG is increased and PAPP-A is decreasedIn trisomy 21 pregnancies at 11-14 weeks, maternal serum free ß-hCG is increased and PAPP-A is decreased• The alterations in maternal serum biochemistry are independent of fetal NT thickness The alterations in maternal serum biochemistry are independent of fetal NT thickness • Screening by fetal NT and serum free ß-hCG and PAPP-A identifies 90% of cases for FPR of 5% Screening by fetal NT and serum free ß-hCG and PAPP-A identifies 90% of cases for FPR of 5%

Maternal serum free ß-hCG & PAPP-A at 11-13+6 wks

Brizot et al 1994; 1995; Liao et al 2001; Noble et al 1995; Spencer et al 1999; 2000; 2001; 2002; 2003; 2004; 2005

• ß-hCG: higher in Africans & IVF pregnancy, lower in smokers; PAPP-A: higher in Africans, lower in IVF & smokers

Biochemistry and screening for trisomy 21Biochemistry and screening for trisomy 21

OSCAR: Fetal NT, maternal serum free ß-hCG OSCAR: Fetal NT, maternal serum free ß-hCG && PAPP-A at 11-13 PAPP-A at 11-13+6+6 wks wks

Nicolaides et al 2005

Normal

Risk Risk >>1 in 3001 in 300

3,909/75,277 ( 5.2%)

Trisomy 21 301/325 (92.6%)

Trisomy 18/13 108/122 (88.5%)

Other defects 83/97 (85.6%)

Singleton pregnancies n=75,821; Maternal age 31 (13-49) yrs

Down syndrome First Trimester


6

5

4

3

2

1

0

Trisomy 18 First Trimester


8

7

6

5

4

3

2

1

0

Turners syndrome First Trimester


8

7

6

5

4

3

2

1

0

Triploidy First Trimester


9

8

7

6

5

4

3

2

1

0

Digynic

Diandric

Combined or Integrated Screening?

CombinedCombined Integrated Integrated

11-13 weeks:11-13 weeks: NTNT NT NT

PAPP-APAPP-A PAPP-A PAPP-A

hCGhCG

15-20 weeks:15-20 weeks: hCG hCG

AFPAFP

UE3UE3

Inhibin AInhibin A

Biochemistry and Screening for Trisomy 21Biochemistry and Screening for Trisomy 21

Triple testTriple test 77%77%

66%66%

Quadruple testQuadruple test 83%83%

75%75%

77%77%

Nuchal translucencyNuchal translucency 34%34%

Integrated testIntegrated test 93%93%

Double testDouble test 71%71%

61%61%

DRDRFPR 5%FPR 5%

00 11 22 33 44 5 66 77 88 99 1010

FPR (%)FPR (%)

00

1010

2020

3030

4040

5050

6060

7070

80

9090

100100

DR (%)DR (%)

Double testTriple test

Quadruple test

Integrated test

90%90%

NT & ß-hCG/PAPP-ANT & ß-hCG/PAPP-A 83%83%

FPR for DR 85%FPR for DR 85%

WaldWald19991999

1.0%1.0%

1.2%1.2%

WaldWald20032003

2.8%2.8%

MaloneMaloneWaldWald20042004

Integrated Screening


CombinedCombined IntegratedIntegrated

Multiphase anxietyMultiphase anxiety

Increased default rateIncreased default rate

Delayed screening resultDelayed screening result

Delayed diagnosisDelayed diagnosis

Late terminationLate termination

High detection rateHigh detection rate

Single visit Single visit

Earlier screening resultEarlier screening result

Early reassurance (for most)Early reassurance (for most)

Early Diagnosis / ToPEarly Diagnosis / ToP

Combined or Integrated Screening?


0.0

20.0

40.0

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80.0

100.0

0.0 2.0 4.0 6.0 8.0 10.0

False Positive Rate (%)

De

tec

tio

n R

ate

(%

)

Comb / Int

NT / quad

tripledouble

Receiver Operator Curves for Down Screening Tests

Wald et al. 2003; Nicolaides et al. 2005


UKNSC ~ benchmark by April 2007 ~ 3% FPR 75% DR

http://www.nelh.nhs.uk/screening/dssp/model_bestpractice.pdf http://www.phgu.org.uk/info_database/diseases/downs_syndrome/downs.html#published http://www.ncchta.org

http://www.nelh.nhs.uk/screening/dssp/model_bestpractice.pdf

http://www.ncchta.org/

Monni:Monni: options of NT or triple testoptions of NT or triple test

information on CVS and Amnioinformation on CVS and Amnio

496 of 500 opted for NT496 of 500 opted for NT

Lancet ‘98Lancet ‘98

Kornmann:Kornmann:

109 2nd trimester screen - 76% would prefer 1st trimester109 2nd trimester screen - 76% would prefer 1st trimester

49 declined 2nd trimester screening - 2 would consider 49 declined 2nd trimester screening - 2 would consider earlierearlier

79 had CVS - 32% would have had 1st trimester screening79 had CVS - 32% would have had 1st trimester screening

Prenat Diagn ‘97Prenat Diagn ‘97

Women’s attitudes towards screening


Mulvey et al. BJOG 2000

Hypothesis: when informed about the rate of miscarriage of Downs

pregnancies, most women would prefer to delay screening.

Results: the clear majority of women wanted the earliest possible

test, even if this only identified pregnancies destined to

miscarry

Women’s attitudes towards screening


SAMSAS©

Fetal loss rate study Age Range First Trimester Fetal Second Trimester Fetal

Years Loss rate (cases) Loss rate (cases)

Hook et al (1995) 16-49 75% (8) 50% (168)

Halliday et al. (1995) 36-43 31% (39) 18% (73)

Macintosh et al. (1995, 1996) 35-48 48% (302) 24% (610)

Bray and Wright (1998) 35-50 31% (341) 12% (1159)

Morris et al. (1999) 16-49 31% (441) 24% (2035)

Snijders et al. (1999) 35-45 31% (221) 21% (317)

Rates of fetal death in Down syndrome pregnancies.

Assume 10% will abort before 2nd TR

(90% progress to 2TR).

OBS prevalence of T21 in 1st TR = 1:347

17,600 pregnancies x 1:347 = 50 cases

45 cases progress to 2nd TR

61.9% Detected in 2nd TR = 27 cases

77.8% Detected in 1st TR= 35 cases

or 8 more viable cases.

SAMSAS©

Spencer Spencer et al.et al. 2002 2002

-0.7-0.7

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00

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Lo

g1

0 P

AP

P-A

or

Fre

e ß

-hC

G (

Mo

M)

Lo

g1

0 P

AP

P-A

or

Fre

e ß

-hC

G (

Mo

M)

55 77 99 1111 1313 1515 1717 1919 2121

Gestation (wks)Gestation (wks)

ß-hCG in Tr21ß-hCG in Tr21

PAPP-A in Tr21PAPP-A in Tr21

NORMALNORMAL

At 10 wks PAPP-A is better

At 14 wks ß-hCG is better

Analytical error in biochemical screening

Gestational Changes in BhCG and PAPP-A in T21

Spencer et al, Ann Clin Biochem 2002;39:567-76.Spencer et al, Ann Clin Biochem 2002;39:567-76.

-0.7-0.7

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00

0.10.1

0.20.2

0.30.3

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0.60.6

Lo

g1

0 P

AP

P-A

or

Fre

e ß

-hC

G (

Mo

M)

Lo

g1

0 P

AP

P-A

or

Fre

e ß

-hC

G (

Mo

M)

55 77 99 1111 1313 1515 1717 1919 2121

Gestation (wks)Gestation (wks)

t-hCGt-hCG

ß-hCGß-hCG

PAPP-APAPP-A

56.365.1OverallOverall

55.660.11414

55.762.61313

55.864.91212

56.566.91111

58.468.81010

62.170.699

67.972.588

TotalFree ßGA (wks)GA (wks)

Detection Rates at 5% FPR(using correct variable separation model)

Screening by PAPP-A & hCG (free ß vs total)Screening by PAPP-A & hCG (free ß vs total)

Spencer et al, Ann Clin Biochem 2003 40;219-31.Spencer et al, Ann Clin Biochem 2003 40;219-31.

8.88.8

4.54.5

6.96.9

9.19.1

10.410.4

10.410.4

8.58.5

4.64.6NORMALNORMAL


Screening performance with difference types hCG


Impact of analytical error in risk assessment

Marker CV LR CV 1 2.5% 7%2 1.5% 4% 3 4-5% 15%4 6-7% 25%

Age 24yCRL 55mm NT 2.2mmfB-hCG 2.50MoM PAPP-A 0.55MoM

Spencer 2003 DS NewsKryptorKryptor DelfiaDelfia Imm 2000Imm 2000

0

50

100

150

200

250

300

350

1 2 3 4

Risk: 1 in….

FMF risk calculation software has specific medians and distributions for Kryptor and Delfia. These systems meet the analytical imprecision criteria.

•Risk Calculation

•MoM values

•Maternal Age

•Gestational Age

•Recurrence Risk

•Singleton vs Twins

•Maternal Weight

•Ethnic Origin

•Smoking

•IVF

•Analytical Imprecision

•NT vs Biochemistry vs Combined vs Integrated

OUTCOME

Documents

Screening “the systematic application of a test procedure to identify individuals at sufficient risk to warrant diagnostic investigations” CVS 12wks Amniocentesis