Every parent anticipates the birth of a healthy baby. However, a minority of newborns (1 in 4000) may suffer from ‘inborn Errors of Metabolism’ (IEM), which if left undetected and untreated, could significantly affect the long term health and development of the child. To this end, The Chinese University of Hong Kong (CUHK) now offers an expanded newborn screening program which can provide early detection of an extensive range of metabolic diseases previously untested for in Hong Kong.
每個父母都期望一個健康寶寶的誕生。然而，少數的新生寶寶 (1/4000) 有可能患上被稱為「先天性代謝缺陷」的疾病 (Inborn Errors of Metabolism; 簡稱代謝病或IEM)，若未能及早被發現和治療，可以對寶寶的健康和發展帶來嚴重的長期影響。為此，香港中文大學現提供一項新生兒篩查計 劃，旨在早期廣泛診斷出這類未曾在香港地區測試過之代謝病。
Latest Update December 2019
More than 67,899 babies had been screened in JHF-Newborn Metabolic Screening Programme since July 2013.
自2013年7月起到目前為止已經有多於 67,899 名嬰兒參與新生兒代謝病篩查計劃
From November 2017 onwards, we accept all newborn babies including preterm babies, to join the newborn metabolic screening programme.
IEMs are genetic defects which prevent some essential enzymes in the body from being produced. As a result, there is deficiency of certain essential components, or accumulation of toxic substances in the body. If these disorders are untreated, they can lead to serious outcomes including learning difficulties, mental retardation, organ dysfunction and even death. Some of these conditions are however potentially treatable nowadays, with effective screening test performed as early as few days after birth.
What kinds of IEM are screened?
The test screens for 30 IEMs belonging to the following categories:
Amino acid disorders
Fatty acid oxidation disorders
Organic acid disorders
Please note that not all IEMs can be screened.
Who needs to be screened?
Every newborn baby is recommended to be screened unless the baby’s health condition is not suitable.
How to screen for and diagnose IEM?
A few drops of blood are collected onto a card by pricking the baby’s heel after completing oral feeding for 1 day, and up to the 7th day of life. Results will be available within a few days.
How accurate is the screening?
The accuracy for the screened IEMs is high. Similar to any laboratory screening test, there is a small chance that some affected infants may be missed (false negatives), while some unaffected infants may be wrongly identified (false positives). Therefore, it is extremely important that all abnormal screening results should be followed by standard diagnostic tests for confirmation.
代謝病篩查的準確性很高。可是，與其他任何一種化驗室篩查技術一樣，在極少的情況下，有些患病的寶寶未能被檢出 (假陰性)，而有些健康的寶寶則會被懷疑患病 (假陽性)。所以，對於所有異常的篩查結果，我們都要進行診斷性的檢測來確認寶寶是否患病。
How are results reported?
Results from the screening will be reported as either:
This indicates that the baby has a very low chance of having one of the 30 IEMs. The majority of babies (98-99%) will have a normal result.
This indicates that the baby is at risk of having an IEM. Immediate referral to a Paediatrician for clinical evaluation, further diagnostic workup and management are needed.
This indicates that the sample analysis is inconclusive and a new sample is needed. This may happen in about 1% of all screened babies. Parents of babies with an ‘uncertain result’ will be contacted to arrange for another sample to be taken.
Why do we do it on blood?
International gold standard
Large worldwide databases of reference ranges and decision cut-offs
We may see slightly abnormal newborn screening results in healthy babies. We call them false positives. Babies with such results have to undergo further confirmatory investigations including blood tests and urine tests to rule out the condition. Therefore false positive results create enormous anxiety to parents.
Proper selection of target diseases is crucial, because
Some IEMs have onset later in life and are untreatable. Making the diagnosis too early only creates insurance issue and psychological burden to the family.
Some IEMs are very mild and does not require treatment or long-term follow-up.
Some important IEMs (e.g. carnitine uptake defect) only produce abnormal metabolites in blood.
The CUHK-BCM Joint Centre for Medical Genetics
The Chinese University of Hong Kong
(852) 5600 1970 (office hours 辦公時間內)
(852) 3505 4219 (voice mail service available during non-office hours 辦公時間以外設有留言服務)