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Disease & prevention > Case 6 Down syndrome > Flashcards

Case 6 Down syndrome Flashcards

1
Q

What is down syndrome?

A
  • Genetic disorder that occurs when there is an extra copy of the chromosome 21 in a person’s cells = total of 47 chromosomes instead of 46.
  • Extra genetic material disrupts normal development and functioning of the body and brain.
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2
Q

What are the 3 types of DS?

A
  • Trisomy 21
  • Transolcation DS
  • Mosaicism
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3
Q

Briefly explain type trisomy 21

A
  • most common type of Down syndrome, accounting for about 95% of cases.
  • extra copy of chromosome 21 in all cells.
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4
Q

Briefly explain transolcation DS type

A

a part of chromosome 21 breaks off during cell division and attaches to another chromosome.

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5
Q

Briefly explain mosaicism

A

extra copy of chromosome 21 is present in only some cells, rather than all cells.

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6
Q

What are risk factors for chromosomal anomalies?

A
  • maternal age
  • higher maternal age = higher risk of chromosomal anomalies
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7
Q

What is a monogenic disorder?

A

cause is a single change in the DNA strand in 1 base pair that is missing/changed, etc.

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8
Q

What is a risk for monogenic disorders?

A

paternal age

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9
Q

*What is the prevalence of DS?

A
  • Due to life style and health care, women are getting children later, but because of tests and medical care you would expected the prevalence to rise, but it does not, so maybe they get abortion
  • Look at number of births with DS in NL, see lower than few years ago
  • Look at number that would have been born if there werent any options for abortion, you would expect the #’s to increase coz maternal age is a risk factor for getting child with DS, women getting children at older ages nowadays, so if abortion was not an option, you would see increase in # of children born with DS.

see graph in docs

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10
Q

What is the incidence of DS?

A
  • In the Netherlands 1 in a 1000 newborns with DS.
  • 35 years old mother: 1 in 350
  • 45 years old mother: 1 in 45
  • Incidence world wide is 1 in 800
  • Because women are getting children later on, there is a higher risk for DS
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11
Q

What are the risk factors for DS?

A
  • Maternal age
  • Certain exposures to certain substances (alcohol, smoking), chemicals
  • Family history
  • When you have a previous child with DS there is a higher risk to get another child with DS (due to age)
  • Most cases happen spontaneously (pure bad luck)
  • Translocation carrier (if parent carries transolcation of chr 21 = at higher risk).
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12
Q

*What are the diagnostics of DS?

karyotype a diagnostic or screening

A
  • Chronic villus sampling (CVS) (sample of cells from placenta & analyse chromosomes)
  • Amniocentesis (sample of cells from amniotic fluid & analyse chromosomes)
  • Ultrasound: nuchal fold → you see how thick it is (by children with DS it is thinner because the neck is closer to the body)
  • karyotyping?
  • Physical appearence when baby is born
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13
Q

What are the symptoms of physical features of DS?

A
  • Round of face
  • Flattened face (and nose)
  • Shorter
  • Different disproportions
  • Straight hair
  • Different eyes (slanted eyes)
  • Small ears
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14
Q

What are the symptoms of mental problems of DS?

A
  • intellectual disabilities
  • mental issues
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15
Q

What are the symptoms of developmental delays of DS?

A
  • Walk differently (because very hypotonic - low muscle town = very flexible)
  • Developmental delays in sitting up, crawling and walking.
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16
Q

What are the symptoms of developmental delays of DS?

A
  • Walk differently (because very hypotonic - low muscle town = very flexible)
  • Developmental delays in sitting up, crawling and walking.
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17
Q

What are the biological symptoms of DS?

A
  • Heart defects
  • Respiratory infections
  • Immune system problems
  • Low muscle tone: why people with DS are very flexible.
  • Vision & hearing problems
  • Thyroid
  • Seizures
  • Premature ageing (Alzheimers disease) - often seen around 50 yrs old but get at earlier age than others.
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18
Q

What is the prognosis of DS?

A
  • Very dependable on symptoms & severity symptoms
  • Average life expectancy is about 50-60 years (but if have heart disease, mortality is very high = die earlier)
  • Can live a happy life & have sometimes independence (due to medical care, education, social support and connected to the severity of symptoms)
  • With early intervention and educational support, many people with Down syndrome are able to achieve developmental milestones, such as sitting, crawling, walking, and communicating.
  • Can also be able to attend school, work, and live independently, depending on their individual abilities and needs.
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19
Q

What is the difference between prenatal screening and prenatal diagnosis?

A
  • Screening tests can help identify pregnancies that may be at higher risk for DS
  • Diagnostic tests can provide a definitive diagnosis of DS
  • If your screening test (NIPT test) is negative, they won’t make a diagnosis test. So only if your screening test is positive, they do a diagnosic test
  • Diagnosis is more invasive & screening is not invasive
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20
Q

What are the types of screening tests?

A
  • NIPT test & cell free DNA, ultrasound
  • Cannot provide a definitive diagnosis and may result in false positives or false negatives.
  • Ultrasound less often performed because relatively non-specific.
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21
Q

What are the types of diagnostic tests?

A
  • Chronic villus sampling
  • Amniocentesis
  • Ultrasound???
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22
Q

When are diagnostics offered?

A

to pregnant woman with risk factors → family history/ genetic condition (positive screening test)

23
Q

What is NIPT?

A

Non-invasive prenatal testing → type of prenatal screening test that uses a small sample of the mother’s blood to detect risk of certain genetic conditions in the fetus, including Down syndrome, trisomy 18, and trisomy 13.

24
Q

*How does NIPT work?

A
  • During pregnancy, small amounts of the baby’s DNA are released into the mother’s bloodstream.
  • NIPT works by analyzing this fetal DNA, which is present in the mother’s blood, to detect any abnormalities.
  • Cell free foetal DNA (from placental) in bloodstream so very non-invasive
  • Broken down fairly quick because for mothers body it is foreign material, so low amount of cell free foetal DNA
25
Q

When is NIPT done?

A

Between 10-13 weeks of pregnancy

26
Q

Benefits of NIPT?

A
  • It is very reliable (for only 3 diseases: trisomy 13, 18 and 21)
  • 99% detection rate and low false positive rate
  • informed reproductive decisions
  • less invasive testing
  • reassurance
27
Q

Limitations of NIPT

A
  • False positive and false negative results do occur.
  • only 3 diseases tested
28
Q

What do results look like/mean for NIPT?

A

See graph
If results abnormal = colour changes → green means too much chromosome 21 present, if red = less

29
Q

When is NIPT not possible in NL?

A
  • <18 years
  • No informed consent because of communication problems
  • No Dutch health insurance
  • Dichorial twin or vanishing twin
  • Known maternal malignant disease
  • Maternal blood transfusion or transplantations or immunotherapy
  • Anomalies on prenatal ultrasound
  • Parental chromosomal anomalies
30
Q

What are the follow-ups for a NIPT test?

A

Positive NIPT = additional testing but depends on circumstances. Otherwise options are:
* Diagnostic testing
* ultrasound (e.g. nuchalfold)
* genetic counselling

31
Q

Why genetic counselling with NIPT?

A
  • provide information and support for parents who receive a positive NIPT result.
  • Can explain results of test, discuss risks & benefits of follow-up testing, & provide guidance for making informed decisions about the pregnancy.
  • Counselling is very focussed on what parents want and need to know. Prepare the parents for a child with DS (both medical and social)
32
Q

What happens when the NIPT is abnormal?

A

NIPT abnormal = abnormal screening → not diagnosis of trisomy 21 but highly likley that there is trisomy 21 therefore diagnostic testing is offered

33
Q

**Why don’t use chronic villus sampling after NIPT?

idk if this is correct

A
  • has to do with technique
  • if you find foetal DNA in mothers blood, it can be from foetus itself but sometimes there is a trisomy which is only present in the placental cells and not in the baby.
  • If you do chorionic villus sampling which is placental material, you could get a false positive result because the baby does not have trisomy 21
34
Q

What are the benefits of screening in general?

A
  • Reduced anxiety
  • Preparation for birth
  • Better medical management
  • Early detection and treatment = early intervention and treatment, which may improve health outcomes.
  • Peace of mind: Provide reassurance & peace of mind for individuals who are concerned about their health.
  • Preventive care: can help identify individuals at increased risk for certain health conditions = allowing them to take steps to prevent or reduce their risk.
35
Q

What are the risks of screening in general?

A
  • False positives => unnecessary follow-up testing = additional risks and anxiety.
  • False negatives => false sense of security & delay diagnosis and treatment.
  • Overdiagnosis: Screening can detect health conditions that may never cause symptoms or harm = unnecessary treatment and potential harm.
  • Physical harm: Some screening tests e.g. invasive diagnostic tests (CVS, amniocentesis) carry small risk of infection, bleeding, and miscarriage.
  • Emotional harm: + screening result = anxiety & emotional distress, even if further testing reveals that no condition is present
36
Q

What would be the benefits of making the NIPT-Test a routine for screening?

A
  • Increased detection of genetic conditions: could increase # of cases detected & earlier diagnosis and treatment.
  • Decreased need for invasive diagnostic testing: NIPT is non-invasive & does not carry same risk of miscarriage as invasive diagnostic tests. Reduce # of women who need to undergo invasive diagnostic testing.
  • Improved patient outcomes: Earlier detection = improved patient outcomes, incl better management of health conditions and improved QoL.
  • Reduction in healthcare costs: by avoiding unnecessary invasive testing and identifying health conditions earlier.
37
Q

What would be the risks of making the NIPT-Test a routine for screening?

A
  • Stress
  • social pressure to have a perfect child
  • Higher chance of abortion if everybody gets screened = less children with DS
  • false positives
  • overdiagnosis
  • ethical concerns - discrimmination against individuals with genetic conditions & selective termination of prgenancies based on presence of a genetic condition.
  • Increase in ggenetic counselling and support services.
  • Impact on healthcare resources incl lab capacity & genetic counselling services.
38
Q

What is validity?

A
  • Validity test ability to distinguish those who do and don’t have a disease.
39
Q

What is sensitivity?

A
  • measure of a test’s ability to correctly identify individuals with a condition.
  • highly sensitive test will correctly identify almost all individuals with the condition & have a low false-negative rate.
40
Q

What is specificity?

A
  • Specificity is a measure of a test’s ability to correctly identify individuals without a condition.
  • A highly specific test will correctly identify almost all individuals without the condition and will have a low false-positive rate.
41
Q

What is positive predictive value?

A
  • probability that subjects with a positive screening test truly have the disease.
  • affected by both the sensitivity & specificity of test & prevalence of the condition in the population being tested.
42
Q

What is positive predictive value?

A
  • probability that subjects with a positive screening test truly have the disease.
  • affected by both the sensitivity & specificity of test & prevalence of the condition in the population being tested.
43
Q

What is negative predictive value?

A
  • probability that subjects with a negative screening test truly don’t have the disease.
  • affected by both the sensitivity & specificity of test & prevalence of the condition in the population being tested.
44
Q

What are some struggles as a genetic counsellor?

A
  • Lots of general information - what is applicable for which couple?
  • Not much (or not) certainty
  • Non-directive counselling - have to be very objective
  • Put emphasis on things that are normal
  • When is it too much or not enough
  • Future: stigma / view on children with DS
  • a lot of parents dont care about #’s but if child is affected or not.
45
Q

What is categorical objection?

A
46
Q

What are arguments of critics for the categorical ethical objections to prenatal screening for DS?

A
  • possible aims of prenatal screening: “all problematic”?
  • abortion
  • ‘disability rights’ critique
  • ‘radical’ feminist critique
47
Q

What do the critics mean by aims of prenatal screening being problematic?

A
  • Aim linked with serving public health/ cost reduction
  • Aim is preventing serious suffering of affected child → not all affected suffer seriously/as bad as someone else.
  • Promoting repdroductive autonomy → but then sex-selection for non-medical reasons.
48
Q

What are the arguments given about abortion?

A
  • View 1: absolute moral value: abortion = murder
  • View 2: no moral value: abortion is morally neutral / indifferent
  • View 3: relative moral value (dominant view): abortion may be the less of 2 evils → all depends on the reasons, context that there may be to terminate pregnancy.
49
Q

What are the arguments about disability rights critique?

A

want to get rid of all peopel with DS?

50
Q

What are the arguments about ‘radical’ feminist critique?

A
  • Value of natural pregnancy - makes it almost impossible for pregnant women to bond with their future child before having a test result
  • Dangers of so-called “medicalisation”:
    Disproportionate concerns/anxieties regarding future children’s health
    Lack of respect for women’s autonomy
51
Q

what are ethical issues with reagrds to NIPT prenatal screeing?

A
  • ‘Routinisation’ of prenatal screening → people may wrongly consider NIPT to be a simple test and part of prenatal care because for couple can still confront them with challenging, controversial dilemmas.
  • Costs of prenatal screening → inequity/unequal access
  • What about incidental findings?
52
Q

What are similarities among countires regarding NIPT?

A
  • Cost as a barrier to equitable access
  • Shortage of resources that promote informed choice
53
Q

What are differences among countries with regards to NIPT?

A
  • Highly different regulations of pregnancy termination
  • Different attitudes towards ‘disability rights’
  • A revival of ‘eugenics’/the ‘prevention paradigm’? - making use of NIPT with a clear message of wanting to get rid of DS
  • Different regulations and attitudes regarding sex selection/’family balancing’
  • Impact of commercialization on ethical care.

Disease & prevention (10 decks)

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