Neonatal Screening Flashcards
What is the definition of screening?
the process of identifying apparently healthy individuals who may be at increased risk of a disease or condition
What is the purpose of screening?
by identifying people at an increased risk of a condition, they can be offered information, further tests and/or treatment to reduce their risks and/or complications
What is meant by screening never being 100% sensitive or specific?
sometimes there are false positives/negatives not every person with a condition is identified and sometimes they are identified incorrectly
What criteria are screening programmes based on?
Wilson and Jungner criteria
What are the 5 principles introduced in the Wilson and Jungner Criteria?
- disease must be sufficiently common 2. natural history must be known 3. early therapeutic intervention must be beneficial 4. screening test must be acceptable and affordable 5. there must be a diagnostic confirmatory test
When are babies in the UK screened?
5 days after birth (5 to 8 days in exceptional circumstances)
What details on the neonatal screening card allow the card to be booked in correctly?
- NHS number 2. name 3. address 4. date of birth 5. GP details 6. mother’s details
What details on the neonatal screening card ensure that accurate results are reported?
- date of birth 2. date of sample 3. gestation (premature?) 4. transfusion status 5. hospital status 6. repeat status
Why is hospital status included on a neonatal screening card?
it allows you to find the child if a repeat test is needed
How is a neonatal screening test performed?
blood spots are collected and 3mm discs are punched from the spots usually 4 samples are taken
Why are these examples of poor quality spots?
- too small
- many small spots have been dropped to make a larger spot
- not fully penetrated onto the other side of the paper
Why are these examples of good quality spots?
they have fully permeated through to the other side of the paper and they fill the entire circle
What are the screening standards relating to being timely?
- timely collection of samples
- timely collection of repeats
- timely processing of samples and reporting data
What are the other 2 screening standards that define best practcie?
- all positive cases to be on treatment with referral within 3 days and by a set time frame
- all babies to be tested, including those identified as missed or coming into the country, up to one year of age
What are the 5 conditions on the UK screening programme that have been screened for for a long time?
- phenylketonuria (PKU)
- congenital hypothyroidism
- sickle cell and Hb disorders
- cystic fibrosis (CF)
- Medium-chain acyl-coenzyme A dehydrogenase deficiency (MCADD)
What are the 4 expanded screening conditions on the UK neonatal screening programme?
- maple syrup urine disease (MSUD)
- isovaleric acidemia (IVA)
- homocystinuria
- Glutaric aciduria type 1 (GA1)
How many births are affected by phenylketonuria?
What happens if it is left untreated?
1 in 10,000 caucasian births
it leads to severe intellectual disability if untreated, but there is an excellent prognosis if treated from birth
What is the screening test for phenylketonuria?
bloodspot phenylalanine
How is a diagnosis of phenylketonuria confirmed?
through plasma phenylalanine measurements
(there is no need to measure enzyme or DNA)
What are the 5 main symptoms involved in the natural history of untreated PKU?
- severe intellectual disability
- seizures and tremors
- spasticity
- behavioural problems and irritability
- eczema in childhood
What is the main treatment for PKU?
low phenylalanine diet with careful monitoring
What are the risks with a low phenylalanine diet?
- risk of tyrosine insufficiency
- risk of vitamin and trace element deficiencies
Why might biopterin in the form of saproterin be given to patient’s with PKU?
biopterin is the cofactor for phenylalanine hydroxylase (the deficient enzyme)
if there is any residual enzyme activity left, this will stimulate enzyme activity and increase the amount of protein that the patient can eat
What types of amino acids need to be supplemented in PKU?
large neutral amino acids involved in brain development
Val, Leu, Ileu