GEN 658 General Knowledge Deck

Question 1

what is the definition of screening?

Answer 1

identifying a small group from a large group to offer a more specific test

Question 2

what is sensitivity in a screening test?

Answer 2

number of patients with a positive test who have a disease
_________________________________________________

all patients who have the disease

Question 3

what is the definition of specificity?

Answer 3

number of patients with a negative test and who do not have the disease
_________________________________________________

all patients who do not have the disease

Question 4

what is the screen positive rate?

Answer 4

the % of the population with a positive result (includes true and false positives)

Question 5

what is the false positive rate?

Answer 5

proportion of people with a positive test result who are actually unaffected

Question 6

what is the Negative Predictive Value (NPV)?

Answer 6

the probability that someone with a negative screening test will truly not have the condition (not fixed, depends on the individual’s actual risk before the screen)

Question 7

what is the Positive Predictive Value (PPV)?

Answer 7

the probability that someone with a positive test will actually have the condition (not fixed, depends on the individual’s actual risk before the screen)

Question 8

in first trimester biochemical screens, what hormone profiles would you expect to see for trisomy 21?

Answer 8

high HCG, low PAPP-A

Question 9

in first trimester biochemical screens, what hormone profiles would you expect to see for trisomy 18?

Answer 9

low HCG, low PAPP-A

Question 10

how does maternal weight affect biochemical hormone levels like HCG and PAPP-A?

Answer 10

higher maternal weight = more blood volume. Therefore the hormones will be more diluted, and levels will be lower compared to people with lower weight

Question 11

what are some confounding variables that affect hormone levels like HCG and PAPP-A?

Answer 11

1. gestational age (after 9 weeks less HCG, more PAPP-A
2. maternal weight
3. fetal sex (more HCG and PAPP-A in females than males)
4. multiple pregnancies (twins = 2x hormone levels)

Question 12

what are the incident rates of Turner syndrome

Answer 12

1 in 4000 female live births

Question 13

what are some characteristics of Turner syndrome?

Answer 13

1. webbed neck
2. short stature
3. wide spaced nipples, broad shield-like chest

Question 14

what are the incident rates of Klinefelter syndrome?

Answer 14

1 in 1000 liveborn males

Question 15

what is the incidence of Down’s syndrome?

Answer 15

1 in ~700 newborns

Question 16

what are some clinical features of Down’s syndrome?

Answer 16

1. hypotonia (low muscle tone)
2. small stature
3. hyperflexibility
4. learning disability

Question 17

what are some things about the hands and feet in Down’s syndrome?

Answer 17

1. transverse palm crease in hands
2. clinodactyly (curved pinky finger)
3. wide gap between first and second toes

Question 18

what are some common health problems in Down’s syndrome?

Answer 18

1. cardiac malformations (50%)
2. GI & anal atresia (can be fixed with surgery)
3. thyroid problems (hypo = 30-40% lifetime risk)
4. hypotonia (almost 100%)

Question 19

what are the types and incident rates of Down’s syndrome?

Answer 19

95% nonfamiliar trisomy 21 (random nondisjunction in mitosis or meiosis)

3-4% Robertsonian translocations (of which 75% are de novo)

1-2% mosiacism (mitotic nondisjunction)

Question 20

what are the incident rates of Edward’s syndrome (trisomy 18)?

Answer 20

1 in 7,000 live births

Question 21

what are some features of Edward’s syndrome?

Answer 21

1. clenched hands
2. unusual ears
3. prominent occiput
4. cardiac problem: ventricular septal defects (holes in septum which is the heart wall)

Question 22

what is the incident rate of Patau syndrome (trisomy 13)?

Answer 22

1 in 12,000 live births

Question 23

what are some features of Patau syndrome?

Answer 23

1. cleft lip/cleft palate
2. clenched hands
3. malformations of CNS
4. CHD
5. microcephaly
6. rocker bottom feet

Question 24

what is the most common microdeletion?

Answer 24

22q11.2

1 in 4000 live births

Question 25

what are some clinical features of 22q11.2?

Answer 25

1. cardiac defects
2. cleft palate
3. thymus hypo/hyperplasia
4. developmental delays

Question 26

which chromosomes are acrocentric?

Answer 26

13, 14, 15, 21, 22