Baby’s Health: What Is the Guthrie Test
The Guthrie test detects five rare, invisible diseases in babies after birth. It requires a blood sample at the heel.
Let’s look in detail at how it’s done and why.
How the Guthrie test is performed
The Guthrie test is performed after 72 hours of your baby’s life because your baby must have been fed for a few days to avoid false positives. Nine drops of blood are taken from the baby’s heel, sometimes from the hand, which avoids the need to take blood. The drops of blood are put on a blotter and sent to the laboratory for analysis to look for certain diseases. The results are available by the end of the first week of life, which allows treatment to be started quickly if one of the tests is positive.
This test has been around for about 40 years. In the beginning, it only detected phenylketonuria. Now, it also sees:
congenital adrenal hyperplasia;
sickle cell disease.
Guthrie test and cystic fibrosis
The Guthrie test for this genetic disease has been available since 2002. If the test proves positive, it is confirmed by the sweat test and a genetic test with the parents’ authorization for the latter.
One child in 2,000 to 2,500 is born with cystic fibrosis. This disease is the leading cause of severe respiratory insufficiency in children (severe coughing, disturbing sleep, and eating). The viscosity of the glandular secretions causes these respiratory and digestive disorders. The diagnosis of the disease is difficult.
The Guthrie test measures the blood’s pancreatic enzyme called trypsin.
There is no specific treatment to cure this disease. Early management reduces the clinical signs.
Screening for phenylketonuria by the Guthrie test
It is a severe metabolic disease caused by the deficiency of a hepatic enzyme that allows the transformation of an amino acid, phenylalanine, into another tyrosine. Phenylalanine increases in the blood because it cannot be transformed and causes brain disorders. It concerns one birth out of 15 000. This disease is treated by a diet that must be started quickly to avoid mental retardation, behavioral disorders, psychosis, and epilepsy…
The Guthrie test allows for measuring phenylalanine. If the level is high, more advanced tests will confirm the diagnosis. The diet aims at limiting the level of phenylalanine in the blood. It is low in foods containing phenylalanine: meat, fish, milk, and eggs…
Guthrie test: congenital hypothyroidism
It is an endocrine disease caused by a lack of production of a thyroid hormone, thyroxine, which can cause mental retardation.
The Guthrie test measures the level of TSH in a drop of blood. When thyroxine is not sufficiently secreted, the pituitary gland produces too much TSH.
Daily treatment for life consists of taking oral thyroxine. However, not all children with confirmed hypothyroidism will receive treatment for life. Some have a brief form in a proportion that varies from 10 to 35%. International recommendations are to confirm the diagnosis of congenital hypothyroidism after the 2nd birthday, after a 4-6 week break in treatment.
Guthrie test: congenital adrenal hyperplasia
The Guthrie test for this disease has been available since 1996.
It is caused by an abnormal production of hormones in the adrenal glands, which leads to a defect in the secretion of cortisone and, in some cases, of hormones that retain water and salt in the body, as well as an excessive production of male hormones, which causes dehydration, growth problems…
The lifelong treatment is to take adrenal hormones to help the growth and normal development of the child.
The Guthrie test measures the level of 17-hydroxyprogesterone.
Guthrie test: sickle cell disease
The abnormal hemoglobin causes this disease, hemoglobin S. It is mainly found in Africa, the West Indies, and the Mediterranean basin.
Sickle cell disease causes pain, infections, and severe anemia, especially in children under 2 or 3 years of age.
The Guthrie test shows the presence of hemoglobin S. It is performed on newborns whose parents are from at-risk countries and babies born in overseas departments and territories.
Antibiotic treatment and vaccination against infections can prevent disorders in the first years of life.
Results of the Guthrie test
You will not be informed if the results are negative. However, your doctor will contact you if they are positive to perform additional tests to confirm the diagnosis and then begin treatment.