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LMP301 > LMP301 Lecture 19: Newborn Screening > Flashcards

LMP301 Lecture 19: Newborn Screening Flashcards

1
Q

when does newborn screening happen?

A

first 1-2 days of life

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2
Q

what is used for newborn screening?

A

blood from heel of infant

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3
Q

newborn screening procedure

A
  1. collect blood from heel of infant
  2. dot on filter paper
  3. send to newborn screening program along with baby/family info (usually in country capital)
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4
Q

PKU

A

phenylketouria

= phenylketones in the urine

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5
Q

can PKU be treated?

A

yes

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6
Q

symptoms of PKU

A
  • mental retardation
  • blond hair (even if not in family)
  • low IQ (35)
  • smell (phenylpyruvate, phenylketones in urine)
  • decreased pigmentation
  • seizures
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7
Q

what is the toxic material in PKU?

A

Phe

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8
Q

Phe causes acute toxicity if greater than…

A

1300 uM

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9
Q

what is the consequence of excess Phe?

A
  • build up in blood
  • acute toxicity
  • affect brain development
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10
Q

PKU is a ___ disorder

A

Phe metabolism

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11
Q

PKU is caused by…

A

deficiency of phenylalanine hydroxylase (PAH)

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12
Q

pheylalaline hydroxylase

A

Phe -> Tyr

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13
Q

“-emia”

A

in the blood

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14
Q

what happens when Phe can’t be converted to Tyr?

A

converted to phenylketones instead

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15
Q

what type of disease is PKU (genetics)

A

autosomal recessive

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16
Q

incidence of PKU

A

1 in 10 000

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17
Q

incidence of PKU carrier

A

1 in 50

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18
Q

why is decreased pigmentation in those with PKU?

A

lack of Tyr, which is metabolized to produce melanin

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19
Q

why is there decreased mental capabilities in those with PKU?

A
  • Phe is toxic to brain development

- missing many NT due to lack of Tyr

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20
Q

what can be used to examine amount of Phe in the blood?

A

ultra-performance liquid chromotography

  • separate all AA in blood and see levels of each
  • see if Phe exceeds normal level
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21
Q

what type of testing is used to determine PKU?

A

chromotography

NO genetic testing

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22
Q

is genetic testing used to diagnose PKU?

A

no

23
Q

treatment of PKU

A

dietary: limit Phe in diet

this will prevent mental retardation

24
Q

when should treatment for PKU begin?

A

during first 10-12 days of life, and is lifelong

25
Q

which foods should PKU patients avoid?

A
  • protein (meats, fish, eggs, poultry)

- bread, potatoes, vegetables (restricted based on individual tolerance)

26
Q

which group really needs to watch their Phe intake if they have PKU?

A

pregnant women: may affect baby brain development

27
Q

what is it called when a baby is mentally retarded due to mom not taking care of diet during pregnancy?

A

Maternal PKU

  • mental abilities affected
  • baby does not necessarily have PKU
28
Q

beside defects in PAH, what may also cause PKU?

A

biopterin defects (problems with co-factors that help PAH)

29
Q

mutations/defect in ___ will result in cofactors that cannot support action of PAH

A
  • GTPCH
  • PTPS
  • DHPR
  • PCD
30
Q

PTPCH

A

GTP cyclohydrolase

31
Q

PTPS

A

pyruvoyltetrahydropteridin synthase

32
Q

DHPR

A

dihydropteridine reductase

33
Q

PCD

A

pterin 4 alpha-carbinolamine dehydratase

34
Q

symptoms of individuals with PKU due to biopterin defects

A
  • mental problems
  • abnormal levels of serotonin & dopamine
  • epileptic crisis
  • seizures
  • lower levels of Phe accumulation (not primary PKU), but equally bad symptoms
35
Q

Biopterin defects account for…

A

5% of all PKU cases

36
Q

how to treat those with PKU due to biopterin defects?

A
  • give biopterin

- will not respond to Phe-restricted diet

37
Q

What is the most common disorder tested for in newborn screening?

A

PKU

38
Q

difference between newborn screening (NBS) and testing

A

NBS is performed on every newborn, but testing is only for those who are suspected of having a disease (results from screening, family history, symptoms)

39
Q

define: NBS

A

testing of ALL newborn children in order to detect diseases for which early intervention is available, necessary, and alters course of the disease

40
Q

there is no point testing for which types of diseases?

A

diseases with no treatment options

41
Q

about how many diseases are screened?

A

30

42
Q

criteria for the type of disease screened

A
  1. high frequency disease
  2. know disease history (what happens if disease is untreated)
  3. disease causes significant morbidity/mortality
  4. treatable, and treatment improves outcome
  5. testing is safe, simple, sensitive, fast
  6. confirmatory testing is available
  7. cost-effective
43
Q

what technique is used for newborn screening?

A

tandem mass spectrometry

  • inject plasma into mass spec
  • ionized
  • AA separated based on weight (look at combined weight of elements that make up that AA)
44
Q

MW of Phe

A

165.08

45
Q

benefits of using mass spec as testing method

A
  • fast (results out in 24-48h)
  • sensitive, specific
  • automated
  • many samples examined at same time
  • many disorders examined at same time
46
Q

are NBS tests diagnostic?

A

no

47
Q

NBS process

A
  1. obtain sample
  2. send to neonatal screening program
  3. test
  4. results
  5. contact family (if needed)
  6. direct to physician
  7. confirmatory testing
  8. follow-up
  9. counselling
48
Q

what has to be considered if NBS screen tests positive?

A
  • test family members (because all diseases screened are of genetic origin)
  • counselling
  • management of disease
  • risk in future pregnancies
  • alternative methods of future reproduction
49
Q

congenital hypothyrodism causes…

A

mental retardation

50
Q

MCAD

A
  • high frequency disorder
  • sudden infant death due to inability to break down FA
  • hypoglycemic
  • can’t break down FA to ketones, so no energy to brain when fasting (e.g. sleep)
51
Q

treatment for MCAD

A

wake up kid every few hours to eat

52
Q

which type of screening is performed for cystic fibrosis?

A

both biochemical & genetic screening

  • 2 types of screening
  • only for this disorder
53
Q

TMS

A

tandem mass spectrometry

LMP301 (18 decks)

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