Frequently asked questions
Newborn metabolic screening is a way of identifying babies with an increased risk of having rare but serious disorders known as metabolic disorders. Metabolic disorders do not usually show any signs or symptoms at birth, and are difficult to identify without a blood test. Babies identified through screening as having an increased risk of a disorder need diagnostic testing to confirm if they have a disorder.
Your Lead Maternity Carer (LMC) or midwife will discuss newborn metabolic screening with you and ask for your consent for it to be done. If you consent on behalf of your baby, a blood sample will be taken from them as soon as possible after they are 48 hours old. A few drops of your baby's blood will be taken from their heel and placed on a blood spot card. Information relating to your baby will be written on the card, and the sample will be sent to the laboratory to be tested for 23 metabolic disorders.
The ‘heel prick test’ is when a blood sample is taken from a baby’s heel so that the baby’s blood can be tested for certain metabolic disorders. The blood sample is taken using an automated device called a lancet. The lancet is used to make a small puncture on the side of the baby’s heel. The baby's foot is then allowed to hang down to increase the blood flow, and a blood spot card is used to collect the blood sample. After the 'heel prick test' is completed, gentle pressure is applied to the baby’s foot using cotton wool to stop the bleeding.
A blood spot card, or 'Guthrie' card, is a postcard-sized card with special paper (specimen collection paper) for collecting and holding four spots of blood. The blood spot card has two parts, a smaller part with the specimen collection paper for the blood sample, and a larger part for information about the baby. The two parts are separated by a perforation. When the card with the blood sample is received by the laboratory, a unique identification number is placed on both parts of the card and the laboratory separates the blood spot part from the rest of the card for testing.
The Newborn Metabolic Screening Programme screens newborn babies for 23 metabolic disorders:
- amino acid disorders (9 disorders, including PKU and MSUD)
- fatty acid oxidation disorders (8 disorders)
- Congenital hypothyroidism (CH)
- Cystic fibrosis (CF)
- Congenital adrenal hyperplasia (CAH)
- Biotinidase deficiency
- Severe combined immune deficiency (SCID).
For more information on the disorders see the pamphlet Your Newborn Baby's Blood Test
Almost all babies born in New Zealand have newborn metabolic screening (about 64,000).
Your Lead Maternity Carer will talk to you about the screening test and give you the opportunity to ask questions. Your Lead Maternity Carer will also give you a brochure containing information about the Newborn Metabolic Screening Programme . If you agree to the test being done, a few drops of blood will be taken from your baby's heel (sometimes called the 'heel prick test' or 'Guthrie test') and collected onto a blood spot card. The blood sample is dried and sent to the laboratory for testing.
The blood sample is taken by a Lead Maternity Carer, hospital midwife, or trained blood taker (phlebotomist).
Metabolic disorders often do not show any symptoms until damage has occurred. Screening can detect these disorders before symptoms appear, and early treatment can be available to your baby.
Yes. Most babies with the metabolic disorders screened by this programme show no obvious signs or symptoms immediately after birth. For each of these disorders there is a problem in one of the biochemicals which are produced naturally in the baby's body. Without a blood test these problems are hard to identify. Screening can detect these disorders before symptoms appear, and early treatment can be available to your baby.
The Ministry of Health strongly recommends screening for all newborns.
The blood sample should be taken when your baby is 48 hours old, or as soon as possible after this (and before they are 72 hours old). The sample may be taken either in hospital or at home.
When a baby with a metabolic disorder is in the womb, the placenta clears away any abnormal biochemical levels as the baby’s system produces them. When the baby is born, the baby’s own system takes over and if the baby has a metabolic disorder, the biochemicals can accumulate to toxic levels or cause other problems. The baby’s own system should be working properly at 48 hours of age, and this is therefore the best time to test the baby for metabolic disorders: when your baby’s system is working independently, and before your baby gets sick.
The LMC is responsible for:
- talking to parents/guardians about newborn metabolic screening
- answering any questions parents/guardians have about the programme
- ensuring that parents/guardians give informed consent for screening and to make a decision regarding storage
- documenting consent or decline to screening
- documenting consent or decline to storage and possible future uses of blood spot cards
- ensuring that other health professionals are aware of declines (when parents choose not to have screening)
- taking the blood sample (or ensuring it is taken)
- providing any follow-up required by the programme, such as taking repeat samples and reporting results.
Newborn metabolic screening is free to all eligible babies born in New Zealand. See the Ministry of Health website for eligibility criteria relating to publicly funded services.
Your LMC or midwife will have your baby's results within ten days if they are negative.
If a result is positive, the laboratory will telephone your LMC or midwife and they will let you know as soon as possible so that your baby can be referred to a specialist.
Yes, newborn metabolic screening is voluntary. Your Lead Maternity Carer or midwife can talk about any concerns or questions you have. Your health professionals (well child provider, doctor) should be advised if your baby has not been screened.
Yes, you can ask for your baby's blood spot card back after screening is complete or at any time in the future. If you would like to request your baby's blood spot card, please download and complete the form below and send it to the laboratory. You will be sent the top part of your baby’s blood spot card with the specimen collection paper holding the blood sample.
Parents/guardians or individuals of age can request the return of blood spot cards at any time using the 'Return of newborn metabolic screening samples ('Guthrie card' or 'blood spot card') to family request form'.
Seven small spots of blood are punched out of the card. One of these spots is used to test for the 17 amino acid and fatty acid oxidation disorders using the tandem mass spectrometer. The other punched spots are used to test for the other six disorders. The leftover blood is either tested again if there is a problem with the first result, held in secure storage or returned to the family/whanau at their request.
Any blood left over after screening 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 make improvements to the screening programme
- to investigate unexplained illness or death in a family/whanau
- for forensic use (identifying a deceased or missing person or assisting with enquiries such as identifying victims of a natural disaster or crime). This is governed by a Memorandum of Understanding with the New Zealand Police
- for research approved by an ethics committee. To date, blood spot cards have not been used for large scale population studies.
The Newborn Metabolic Screening Programme 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 approval
- the study must be presented to the Programme Governance Team
- 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.
When screening is complete, the blood spot card is either returned to the family/whanau if requested or stored indefinitely in a secure locked area. Parents/guardians or individuals can request the return of their blood spots at any time using the 'Return of newborn metabolic screening samples' form available on the NSU website. Only authorised staff from the screening programme can access stored blood spots.
Repeat samples are needed for about one in every fifty babies. Repeat samples are needed if there was too much or not enough blood collected, the sample was contaminated or took too long to reach the laboratory, or the result showed an increased risk for one of the disorders. If this happens with your baby’s sample, your Lead Maternity Carer will contact you and request another blood sample be taken from your baby's heel.
Most repeat samples are negative. This is usually because the first sample had too much or not enough blood, was contaminated (eg, with baby powder or lotion), or took too long to reach the laboratory, and the test result was not accurate. If the baby's metabolism is slightly delayed, this may also cause an inconclusive reading. In these cases the repeat sample will usually give a negative result.
There are a number of reasons for an abnormal result. The blood sample may have been contaminated, too much or not enough blood may have been taken, or the sample may not have reached the laboratory quickly enough. The sample may also have been 'borderline', which means it was not possible to tell whether or not there was a problem. In these cases, your Lead Maternity Carer will talk to you about taking a repeat sample.
The result may also have been abnormal because your baby has an increased risk of having one of the disorders screened for. If this happens, the laboratory will contact your Lead Maternity Carer. Diagnostic testing will be necessary to confirm the diagnosis. This will be managed by a paediatrician who will explain the process and results.
Many of the effects of disorders can be reduced, either by diet or medication. Treatment is best if started early.