GEN 658 General Knowledge Deck Flashcards
what is the definition of screening?
identifying a small group from a large group to offer a more specific test
what is sensitivity in a screening test?
number of patients with a positive test who have a disease
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all patients who have the disease
what is the definition of specificity?
number of patients with a negative test and who do not have the disease
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all patients who do not have the disease
what is the screen positive rate?
the % of the population with a positive result (includes true and false positives)
what is the false positive rate?
proportion of people with a positive test result who are actually unaffected
what is the Negative Predictive Value (NPV)?
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)
what is the Positive Predictive Value (PPV)?
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)
in first trimester biochemical screens, what hormone profiles would you expect to see for trisomy 21?
high HCG, low PAPP-A
in first trimester biochemical screens, what hormone profiles would you expect to see for trisomy 18?
low HCG, low PAPP-A
how does maternal weight affect biochemical hormone levels like HCG and PAPP-A?
higher maternal weight = more blood volume. Therefore the hormones will be more diluted, and levels will be lower compared to people with lower weight
what are some confounding variables that affect hormone levels like HCG and PAPP-A?
- gestational age (after 9 weeks less HCG, more PAPP-A
- maternal weight
- fetal sex (more HCG and PAPP-A in females than males)
- multiple pregnancies (twins = 2x hormone levels)
what are the incident rates of Turner syndrome
1 in 4000 female live births
what are some characteristics of Turner syndrome?
- webbed neck
- short stature
- wide spaced nipples, broad shield-like chest
what are the incident rates of Klinefelter syndrome?
1 in 1000 liveborn males
what is the incidence of Down’s syndrome?
1 in ~700 newborns
what are some clinical features of Down’s syndrome?
- hypotonia (low muscle tone)
- small stature
- hyperflexibility
- learning disability
what are some things about the hands and feet in Down’s syndrome?
- transverse palm crease in hands
- clinodactyly (curved pinky finger)
- wide gap between first and second toes
what are some common health problems in Down’s syndrome?
- cardiac malformations (50%)
- GI & anal atresia (can be fixed with surgery)
- thyroid problems (hypo = 30-40% lifetime risk)
- hypotonia (almost 100%)
what are the types and incident rates of Down’s syndrome?
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)
what are the incident rates of Edward’s syndrome (trisomy 18)?
1 in 7,000 live births
what are some features of Edward’s syndrome?
- clenched hands
- unusual ears
- prominent occiput
- cardiac problem: ventricular septal defects (holes in septum which is the heart wall)
what is the incident rate of Patau syndrome (trisomy 13)?
1 in 12,000 live births
what are some features of Patau syndrome?
- cleft lip/cleft palate
- clenched hands
- malformations of CNS
- CHD
- microcephaly
- rocker bottom feet
what is the most common microdeletion?
22q11.2
1 in 4000 live births
