Newborn Metabolic Screening Programme FAQs

The blood spot sample must be taken when baby is 24 hours old or as soon as possible after this before they are 72 hours old.

When a baby is in utero, they are nourished by the placenta. Many disorders do not show abnormal biochemical levels at birth because the placenta eliminated those chemicals as the baby’s system produced them. This is why babies may be affected by a disorder but born without signs or symptoms.

For effective newborn metabolic screening, the baby must be independent of the mother long enough for the indicator biochemicals to show an abnormality.

For fatty acid oxidation disorders, the catabolic state babies experience after birth - when they lose  weight because they are not yet feeding sufficiently - changes the indicator biochemicals. The fatty acid biochemicals normalise when baby starts eating well. In other disorders like amino acidopathies, the biochemicals will continue to be abnormal and some will rise to toxic levels.

The sample must be taken late enough for the disorders to be detectable, and early enough for the fatty acid oxidation indicators to still be raised.

Advances in technology have meant that high-quality screening can now be achieved in samples collected from 24 hours of age. Collection as soon as possible from 24 hours will support the early detection of time critical disorders.

Once the sample has been taken, the dried sample should be couriered to the screening laboratory so that testing can be carried out as soon as possible.

No, babies on antibiotics can be tested normally.

No.

None.

As babies lose birth weight, they break down body protein and this will raise the indicator metabolites in amino acid disorders. In addition, tandem mass spectrometry enables the measurement of more than one indicator for each disorder and this makes screening more sensitive and specific. For example, PKU screening measures both phenylalanine, the substrate, and tyrosine, the product of the enzyme, phenylalanine hydroxylase that is missing in PKU.

The baby needs to be old enough for the indicator metabolites to increase but doesn’t need any particular amount of protein feeding.

The laboratory which performs the screening for the programme must be IANZ accredited against the international standard ISO 15189. This is the highest accreditation programme available. Accreditation by International Accreditation New Zealand ensures that the laboratory that carries out these tests is technically competent, has appropriate processes and is using appropriate up-to-date technology. It is an internationally recognised process for assessing the technical competence and effective quality processes.

Accreditation involves checking that the laboratory has processes to ensure staff are adequately trained, that equipment is regularly maintained and has functional checks before each use, and that there are robust processes for tracking specimens, testing and reporting. Overseas experts are regularly brought in to ensure New Zealand processes are of a similar standard to elsewhere in the world.

Part of checking the quality of testing involves ensuring that the laboratory has satisfactory performance on external and internal quality assurance programmes. The laboratory we use for screening participates in programmes from the Centres for Disease Control in America. For further information see the IANZ website.

After testing, the residual blood spots are stored indefinitely in a secure locked area, or returned to parents or guardians, to the person tested if they ask. You can request the return of your baby's or your own blood spots at any time, using the 'Return of newborn metabolic screening samples (Guthrie Cards) to family' form.

Only authorised staff from the screening programme can access stored blood spots.

When a heel prick is performed information is provided on the card. This information includes demographic data like:

• name
• sex
• birth date and time
• weight
• mother's details
• Midwife or doctor's details

 This data is entered into a secure information system. Once screening is completed the results of the tests are also captured in the information system. The data is used for screening purposes and is only accessed by authorised personnel. Data is provided to Health NZ | Te Whatu ora for monitoring, evaluation and reporting.

Stored blood spots may be used:

• for repeat testing. If a baby has a disorder but did not have a positive screening result, the blood sample can be tested again to see why this happened
• to improve the screening programme
• to investigate a death or illness in a family
• for victim identification, governed by a Memorandum of Understanding with the New Zealand Police
• for research approved by an ethics committee.

Stored blood spot samples cannot be used for identification of criminals unless there is a court order. This has never occurred in the history of the Programme.

The Ministry of Health has a Memorandum of Understanding with the New Zealand Police regarding disclosure of this information. The Ministry of Health and the New Zealand Police first signed the Memorandum of Understanding in 2006. The Memorandum was reviewed in 2013 with the framework for police requests for access to the blood spots signed in May 2014, and reviewed in May 2019.

To date, blood spot cards have not been used for large scale population studies.

Testing for some screened disorders involves looking for a common change (variant) in a section of DNA (gene). These variants are known to be associated with the disorder.

The testing is limited to only a small number of genes known to be linked to specific screened disorders.

No other genetic testing is done on samples unless first discussed and authorised by the parents, guardians, individual or through legal avenues, for example a court order.

The Policy Framework sets out the requirements for population research studies. These include:

• The study must have ethics committee approval.
• The study must have Ministry of Health or Health NZ | Te Whatu Ora approval.
• The study must be presented to the Programme Governance Team/NMSP Technical Working Group.
• The research may not use up all the blood on an individual's card.
• The research must be considered an appropriate use of residual blood spot samples and contribute to the public good through increased scientific knowledge.

Babies are currently screened for

• amino acid disorders 
• fatty acid oxidation disorders
• congenital hypothyroidism
• cystic fibrosis 
• congenital adrenal hyperplasia
• galactosaemia
• biotinidase deficiency
• severe combined immune deficiency.

For more information about the individual disorders babies are screened for, go to Disorders screened for in the heel prick test