Newborn Screening Tests

The purpose of newborn tests is to screen for serious treatable diseases. Most of the disorders are genetic (inherited). The tests are usually done before the baby leaves the hospital. If the tests are done earlier than 24 hours after the baby is born, a repeat test is recommended at 1 to 2 weeks of age.

The newborn screening tests which are done in the United States a are decided on a state-by-state basis. The most common newborn screening tests in the US include those for hypothyrodism (underactivity of the thyroid gland), PKU (phenylketonuria), galactosemia, and sickle cell disease. Testing for hypothyroidism and PKU is required in virtually all States. Screening for galactosemia and sickle cell disease is required in most states.

Some states in the US mandate tests for other conditions. These include: maple syrup urine disease (MSUD), homocystinuria, biotinidase deficiency, congenital adrenal hyperplasia, MCAD, tyrosinemia, cystic fibrosis, and toxoplasmosis. All these tests are usually done using the same sample of the baby's blood.

Congenital Hypothyroidism

Congenital hypothyroidism (low thyroid activity at birth) affects one in about every 4,000 babies. Most children with it who are not identified and treated promptly after birth develop mental retardation and growth failure, deafness, and neurologic abnormalities. Infants with congenital hypothyroidism who start receiving oral thyroid hormone in the first weeks of life perform normally or near-normally on intellectual testing at 4 to 7 years of age.