2024-10-30 10:11:00
Neonatal screening aims to screen all newborns for certain rare, severe diseases, most often of genetic origin. The challenge is to implement, before symptoms appearappropriate measures to avoid or limit the negative consequences of these diseases on the health of children.
When is this neonatal screening carried out? And where?
This screening is implemented thanks to the Guthrie testaccomplished at the maternity ward (sometimes at home) between 48 and 72 hours after birth.
It presents no danger to the child, is 100% supported by Health Insurance and requires parental consent. The High Authority for Health (HAS) recalls that if this test is not obligatory, a “refusal of screening would be highly detrimental for the child”.
What is the principle of the Guthrie test? How to do it?
The Guthrie test takes the form of a small blood test : doctors take a few drops of blood using a stitching at the heel or the hand of the newborn. These droplets are then placed on blotting paper at specific locations. Once dry, the blotter is sent to the relevant regional neonatal screening center, then sent to an analysis laboratory to check the presence (or absence) of serious and disabling diseases.
How to interpret the results of the Guthrie test?
Guthrie test results can be issued no earlier than the first eight days of the newborn’s life.
If they are negative (in the vast majority of cases), they are not sent to the parents, but will remain available at the secretariat of the Regional Neonatal Screening Center concerned.
In case of positive results
Only in the event of positive results from the Guthrie test do doctors inform the parents. A genetic test will be necessary in particular to confirm the diagnosis. Support is immediate: you will be contacted by the Regional Association for the Prevention of Childhood Disabilities, responsible for neonatal screening in your region. You will then be referred to a specialized medical service. This care is essential, because certain diseases (hypothyroidism, adrenal hyperplasia) benefit from specific early treatment.
What are the different pathologies detected using the Guthrie test?
Since January 2023, neonatal screening has been expanded to seven new diseases. Six diseases were already looked for during this examination. The Guthrie test can now detect thirteen rare and serious diseases.
Phenylketonuriaone of the most frequent and serious genetic diseases (1 in 15,000 newborns), due to the deficiency of an enzyme which transforms phenylalanine present in food. If left untreated, it can lead to severe mental retardation and neuropsychiatric complications.
Congenital hypothyroidism, an endocrine disease which affects 1 in 4,000 newborns, results from insufficient secretion of thyroid hormones by the thyroid gland. If left untreated, it can cause severe mental retardation in children.
Congenital adrenal hyperplasiaa genetic defect in the functioning of the adrenal glands which affects 1 in 12,000 newborns and results in a problem with the synthesis of cortisol (a hormone). If left untreated, this disease can lead to severe dehydration or problems with the development of the genital organs.
The cystic fibrosisa genetic disease that affects 1 in 4,000 newborns, causes severe respiratory infections and digestive complications.
The sickle cell anemiaa genetic hemoglobin abnormality which affects 1 in 3,000 newborns and can result in persistent anemia, vascular complications and repeated infections (a disease particularly prevalent in populations of Afro-Caribbean origin). Initially reserved for children at risk due to the origin of their parents, screening has been generalized to all newborns since November 1, 2024.
Medium-chain acyl-CoA dehydrogenase deficiency or MCAD deficit (Medium-Chain-Acyl-CoA Dehydrogenase), a metabolic disease which affects 1 to 5 newborns out of 100,000 and causes the body to have difficulty using fat as a source of energy. If left untreated, it can cause comas which can lead to the death of the child.
L’homocystinurie : a rare genetic disease characterized by the abnormal accumulation in the body of an amino acid called homocysteine that is toxic to the body. If left untreated, it can cause damage to the eyes, skeleton, vascular system, nervous system and sometimes developmental delay.
Leucinose or maple syrup urine disease: a rare hereditary disorder of branched-chain amino acid metabolism. In the absence of treatment, it is characterized by the rapid onset of eating difficulties, excessively prolonged sleep time, vomiting followed by neurological disorders, abnormal movements and respiratory failure.
Type 1 tyrosinemia : genetic disease linked to the deficiency of the liver enzyme, “fumaryl acetoacetate hydrolase” which allows the normal transformation of proteins contained in food. Without proper diet and treatment, toxic waste accumulates in the body and seriously damages the liver, kidneys and nervous system.
Isovaleric aciduria : genetic disease, also called isovaleric acidemia, linked to the deficiency of an enzyme, “isovaleryl-CoA dehydrogenase”, responsible in the absence of a suitable diet for acute disorders at birth (vomiting, convulsions) or later (delayed growth and/or development).
Glutaric aciduria type 1: genetic disease linked to the absence or insufficient functioning of an enzyme, “glutaryl CoA-dehydrogenase”. In the absence of a special diet, it is the cause of the accumulation of toxic products responsible for acute neurological disorders in infants.
Long-chain fatty acid 3-hydroxyacyl-coenzyme A dehydrogenase deficiency : genetic disease linked to the absence or insufficient functioning of this enzyme. In the absence of treatment and a suitable diet, it is characterized by the occurrence in early childhood of hypoglycemia, liver damage, cardiac and neurological disorders.
The primary carnitine deficiency : genetic disease linked to carnitine transporter deficiency. In the absence of carnitine administration, this deficiency leads to cardiac damage in early childhood, often associated with hypotonia, growth retardation, recurrent hypoglycemic attacks and/or coma.
These pathologies are detected from the same blood samplen, but via different analysis techniques. The arrival of tandem mass spectrometry, a molecular analysis technique, has made it possible to screen for many diseases from a single blood sample, notably the group of diseases known as inborn errors of metabolism. This is why seven new diseases have been newly detected since 2023.
The national newborn screening program started in 1972.At first limited to the detection of phenylketonuria, it extended to congenital hypothyroidism in 1978, to sickle cell anemia in Overseas Territories in 1985 and ten years later in a targeted manner in mainland France, to congenital hyperplasia of adrenal diseases in 1995, cystic fibrosis in 2002, MCAD deficiency in 2020, then seven new diseases in 2023. Since 1972, more than 35 million newborns have been screened as part of the national neonatal screening program and 23,500 newborns were taken care of.
Screening for neonatal deafness in addition to the Guthrie test
Systematic screening for permanent bilateral neonatal hearing loss (SPBN) is officially realized since 2012in addition to the Guthrie test. It is practiced for freewith parental consent and appears essential to the extent that deafness conditions language acquisition and, ultimately, social integration.
Since December 2014, it has been the subject of a separate national screening program which takes place in two phases.
The first phase involves checking the newborn’s hearing. In practice, screening is carried out on both ears at the earliest after the 24th hour of life. A first verification test (called Test1 or T1) is carried out. If there is any doubt about the child’s hearing, a second test (called Test2, T2 or Retest) must be carried out before leaving the maternity ward. “The role of these tests is not to estimate the severity or type of hearing loss but toidentify newborns who require specialist consultation in infant audiology”, specifies Santé Publique France in a report* published in November 2019. Depending on the region, a deferred test (T3) can be carried out after leaving the maternity ward for children for whom it was not possible to conclude with a normal hearing.
In case of anomaliesthe second phase of the program consists of confirming the diagnosis in a health establishment, in private practice or in specialized establishments. Doctors assess the hearing levels of suspected children, the type of deafness (transmission, perception), its nature (unilateral or bilateral) and its severity (mild, medium, severe, profound or total).
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**Interview with Dr. Clara Simon, Pediatric Geneticist, on the Evolution of Neonatal Screening in France**
**Interviewer:** Thank you for joining us today, Dr. Simon. Recent advancements in neonatal screening, particularly the expanded Guthrie test, seem to be a game changer. Can you briefly explain how the Guthrie test benefits newborns?
**Dr. Simon:** Thank you for having me. The Guthrie test is crucial because it allows for the early detection of several serious genetic diseases, which can significantly impact a child’s health if not addressed promptly. By screening newborns within 48 to 72 hours of birth, we can initiate early interventions that prevent severe complications, such as mental retardation in conditions like phenylketonuria and congenital hypothyroidism.
**Interviewer:** You mentioned phenylketonuria — can you elaborate on why it’s particularly important to detect this condition?
**Dr. Simon:** Phenylketonuria, or PKU, is one of the most common genetic disorders detected in newborns, affecting about 1 in 15,000 births. The body lacks the enzyme to process phenylalanine, an amino acid found in many foods. If undiagnosed and untreated, PKU can lead to severe cognitive impairment. Early treatment through dietary management can help affected children lead healthy lives.
**Interviewer:** The Guthrie test can now detect thirteen diseases, thanks to recent updates. What does this expansion mean for public health?
**Dr. Simon:** The expansion of the Guthrie test is a significant public health milestone. With the ability to screen for seven new diseases since January 2023, we’re identifying conditions that, without screening, would often go unnoticed until irreversible damage occurs. This proactive approach not only improves individual outcomes but also reduces the long-term healthcare costs associated with untreated diseases.
**Interviewer:** How are parents informed about the results of these tests, especially if there’s a positive diagnosis?
**Dr. Simon:** If a test result is positive, we contact the parents directly. The next steps would include confirming the diagnosis through additional genetic testing. It’s important that the communication is clear and supportive; these situations can be stressful for families. After diagnosis, immediate support is provided through regional associations specialized in childhood disability prevention.
**Interviewer:** Lastly, for parents considering the Guthrie test for their newborns, what would you advise?
**Dr. Simon:** I strongly encourage every parent to opt for the Guthrie test. It’s safe, painless, and 100% covered by health insurance. While participation is not mandatory, declining the test could significantly jeopardize a child’s future. Early detection is key to overcoming many of these serious health challenges.
**Interviewer:** Thank you, Dr. Simon, for your insights on this vital topic. It’s reassuring to know that advancements in neonatal screening are helping to ensure healthier futures for our children.
**Dr. Simon:** Thank you for having me. It’s essential that we continue to advocate for comprehensive neonatal screening for all newborns.
