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Molecular Diagnostics > Prenatal Screening > Flashcards

Prenatal Screening Flashcards

1
Q

“identifying a small group of individuals from a large group to offer a more specific test”

A

Screening

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2
Q

Sensitivity is:

A

the number of people w/ a positive test divided by number of people the the disease

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3
Q

Specificity is:

A

of people with negative test and don’t have the disease divided by people who don’t have the disease

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4
Q

A screen’s detection rate =

A

% of people with disease that the screen will idnetify

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5
Q

The screen positive rate is:

A

% of population that screens positive

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6
Q

False positive rate:

A

proportion of individuals with a positive screen that are actually unaffected

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7
Q

The screen positive rate includes:

A

includes true and false positives

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8
Q

What is the negative predictive value (NPV)?

A

probability that someone with a negative screening test actually does not have the condition

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9
Q

What is the positive predictive value (PPV)?

A

probability that someone with a positive screening test will truly have the condition

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10
Q

Are PPV and NPV static?

A

No, they depend on how high a person’s initial risk was.

PPV for a women that’s 35 and screen positive for t21 going to be much higher than 20yo women with screen positive result

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11
Q

What is MoM? What is it important?

A

multiple of the median

allows us to compare to the median value for race, ethnicity, gestational age, etc.

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12
Q

AMA is considered:

A

women over the age of 35

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13
Q

When is 1st trimester screening completed?

A

btwn 11-13wks

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14
Q

What analytes are evaluated in first trimester screens? What other measurement is taken?

A

PAPP-A
hCG
nuchal translucency

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15
Q

What crown rump length is ideal for NT measurement?

A

45-84mm

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16
Q

What effect does maternal BMI have on analytes?

A

all concentrations are decreased

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17
Q

What sorts of causes do we see with increased NT?

A 
50% t21
25% trisomy 13 or 18
10% turner syndrome
5% triploidy
10% other
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18
Q

When does the Quad screen typically occur?

A

15-22wks

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19
Q

What proteins are analyzed in the Quad screen?

A

AFP
hCG
Inhibin A
uE3

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20
Q

What produces AFP? When does it peak? What is considered elevated?

A

yolk sac then GI tract and liver of fetus

peaks from wk 10-13 (maternal leves peak in 3rd trimester)

> 2.5MoM

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21
Q

What produces hCG? When does it peak?

A

produced by syncytiotrophblasts

increases rapidly in 1st 8wks, decreases through wk20 then levels off

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22
Q

Which analyte is the most sensitive marker of Down syndrome?

A

hCG

detects 25-50% if used alone

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23
Q

What produces uE3? When does it peak?

What conditions is it seen with?

A

produced by the placenta

steadily increases throughout pregnancy

very low levels in SLO and X-linked ichthyosis

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24
Q

What produces Inhibin A?

A

gonads, corpus luteum, decidua, and placenta

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25
Q

What trend do we see on a Quad screen for a pregnancy affected by Down syndrome?

A

low AFP
low uE3
high hCG
high Inhibin A

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26
Q

What demographic is absolutely critical when screening?

A

gestational age/ estimated due date

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27
Q

When would we recalculate a quad screen result?

A

if date is off by 10-14 days

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28
Q

What is integrated screening?

A

1st trimester NT and PAPP-A

then 2nd trimester Quad screen -> report

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29
Q

What is studied in NIPS?

A

cell-free DNA

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30
Q

Where does cfDNA come from?

A

results from apoptosis

roughly 10% is placental

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31
Q

cfDNA requires a certain % of placental DNA. This is known as the ______. What % is ideal?

A

fetal fraction

10%

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32
Q

what happens if the fetal fraction is too low?

A

there is a no-call result

those individuals have an increased risk of abnormalities

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33
Q

What are the current detection and false positive rates of T21, 13, 18, and monosomy X using cfDNA?

A

T21: 99.7% DR, ;0.04% FPR

t18: 97.9% DR, 0.04% FPR
t13: 99% DR, 0.04% FPR

Monosomy X: 95.8% DR, 0.14% FPR

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34
Q

What are the primary methods of invasive prenatal dx?

A

CVS

amniocentesis

35
Q

When is amniocentesis performed?

A

16-20wks

36
Q

What risks are associated with aminocentesis?

A

1:300-1:500 chance for miscarriage

leakage of amnio. fluid, infection, fetal injury by needle

37
Q

What are potential causes of high AFP?

A

contamination, fetal death, multiple gestations, ventral wall defects, nephrosis, miscalculation of GA

38
Q

When is CVS performed? What is sampled?

A

10-13wks

chorionic villi that originate from trophoblasts (should match fetus DNA)

39
Q

What methods of PGD exist?

A

blastomere biopsy

blastocyst bopsy

40
Q

What protein trends do we see in Trisomy 21 in 1st and 2nd trimester?

A

1st: increased NT, decreased PAPP-A, increase hCG
2nd: decreased uE3, decreased AFP, increased Inhibin A, increased hCG

41
Q

What protein trends do we see in Trisomy 18 in 1st and 2nd trimester?

A

1st: increased NT, decreased PAPP-A, decreased hCG
2nd: decrease uE3, AFP, and hCG; no change to Inhibin A

42
Q

What protein trends do we see in Trisomy 13 in 1st and 2nd trimester?

A

1st: increase NT, decreased PAPP-A and hCG
2nd: 2nd: decrease uE3, AFP, and hCG; no change to Inhibin A

43
Q

What protein trends do we see in a NTD in 1st and 2nd trimester?

A

1st: no change
2nd: highly elevated AFP

44
Q

What level of testing should be offered to all prenatal patient?

A

screening and diagnostic testing

45
Q

What are the limitations seen with Integrated screening?

A

test results are later along in pregnancy

significant drop out (often due to lack of 2nd blood draw)

46
Q

Embryonic age begins:

A

at the point of conception (38wk is full term)

47
Q

Why is full term in gestational age 40 wks vs. 38wks?

A

Dated from LMP (includes two weeks before conception)

48
Q

Antepartum =

A

prenatal period

49
Q

Intrapartum =

A

period of time during labor and delivery

50
Q

Peripartum =

A

last month of gestation and first few months after delivery

51
Q

What is the time range of the 1st trimester?

A

0w1d through 13w6d

52
Q

What is the time range of the 2nd trimester?

A

14w0d through 27w6d

53
Q

What is the time range of the 3rd trimester?

A

28w0d through end of pregnancy 42w0d

54
Q

What the first period of development?

A

Germinal: fertilized egg -> implanted blastocyst (end of week 2)

55
Q

What is the second period of development? What vital process occurs in this period?

A

embryonic (3rdwk-8/10th wk gestation)

Gastrulation and neural tube formation occurs
creation of germ cell layers and neural tube

56
Q

What is the third period of development? What vital process occurs in this period?

A

Fetal (9/11wk-end of pregnancy)

organogenesis occurs in this period

57
Q

When are embryos typically transferred in IVF? Why is this helpful?

A

3-5 days after fertilization

allows us to determine gestational age (2w3d-2w5d)

58
Q

How often are women seen during pregnancy?

A

every 4wks from beginning to wk28

every 2wks btwn 38-36wks

every wk from 36 to delivery

59
Q

Gestational diabetes can be associated with what outcomes?

A

preeclampsia, C-section, respiratory distress

60
Q

What is the purpose of 1st trimester ultrasound?

A

determine viability and accurately date

may help determine chronicity if multiple gestations

61
Q

When and why are 2nd trimester ultrasounds performed?

A

ideally 18-20wks

used to eval anatomy (“anatomy scan”)

62
Q

What is the purpose of 3rd trimester US?

A

re. eval fetal anatomy

may also check fetal growth, well-being, amniotic fluid levels, and fetal position for delivery

63
Q

Gravida means:

A

woman who is pregnant

64
Q

Gravidity is:

A

total # of confirmed pregnancies, regardless of outcome.

65
Q

Parity is divided into ___ sections. They are:

A

4

Term
Preterm
Abortion
Living children

66
Q

Term pregnancies are considered:

A

live or stillbirth @ 37w0d or later

67
Q

Preterm pregnancies are considered:

A

live or stillbirth btwn 20w0d-36w6d

68
Q

Abortions (in pregnancy hx) are considered:

A

SAB, elective termination, and ectopic preg. 19w6d or earlier

69
Q

Living children includes:

A

all living, twins and multi. count individual here unlike others

this doesn’t include adopted children

70
Q

a test with 90% sensitivity would identify:

A

90% of people with the condition

71
Q

The higher the specificity, the less likely you are to get:

A

a false positive

72
Q

How do we describe clinical utility?

A

how useful a test is in determining/changing clinical management of the pt completing the test

73
Q

What analyte pattern might you expect with intrauterine growth restriction?

A

high AFP, inhibin A, and hCg in 2nd trimester

74
Q

What analyte pattern might you expect in a spontaneous miscarriage?

A

very low hCG in 1st trimester

75
Q

what analytes might you expect in confined placental mosaicism trisomy 16?

A

high AFP and hCG in second trimester

76
Q

What would low AFP in the second trimester lead you to believe?

A

preterm birth, stillbirth, miscarriage

77
Q

What outcome is consisten with a cystic hygroma? in first trimester? second?

what other conditions are high on the differential w/ cystic hygroma?

A

aneuploidy

1st: Down syndrome
2nd: Turner syndrome
other: Noonan syndrome

78
Q

If a pt elects cfDNA testing, what should you also offer and why?

A

2nd trimester AFP

look for OTND because cfDNA doesn’t look for hormone/protein levels

79
Q

When can CVS be performed in 2nd trimester?

A

to evaluate for oligohydramnios

80
Q

Why isn’t CVS recommended before 9-10wks?

A

risk of limb reduction

81
Q

What are some of the limitations of CVS?

A

confined placental mosaicism

maternal cell contamination

82
Q

What is a common cause of confined placental mosaicism? What may be a reflex?

A

trisomy rescue

follow up fro potential UPD

83
Q

Why would a pt be given RhoGAM? Why?

A

if they are Rh-

prevent alloimmunization

Molecular Diagnostics (6 decks)

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