Newborn screening tests look for serious developmental, genetic, and metabolic disorders so that important action can be taken during the critical time before symptoms develop. Most of these illnesses are very rare.

In the United States, individual states regulate newborn screening, so the diseases screened for vary considerably from state to state. Most states require three to eight tests, but organizations such as the March of Dimes and the American College of Medical Genetics suggest more than two dozen additional tests.

The most thorough screening panel checks for about 40 disorders. All 50 states screen for congenital hypothyroidism, galactosemia, and phenylketonuria (PKU).

Screening tests do not diagnose illnesses. They identify which babies need additional testing to confirm or rule out illnesses. Good screening tests have a low false-negative rate (if the test is normal, the child should be healthy), but may have a high false-positive rate (as many affected children as possible should test positive, even if this means many healthy children also test positive).

If follow-up testing confirms that the child has a disease, appropriate treatment can be started right away, before symptoms appear.

Screening tests are used to detect a number of disorders, including:

• Amino acid metabolism disorders:
  • Arginosuccinic acidemia
  • Citrullinemia
  • Homocystinuria
  • Maple syrup urine disease
  • Phenylketonuria (PKU)
  • Tyrosinemia type I
• Biotinidase deficiency
• Congenital adrenal hyperplasia
• Congenital hypothyroidism
• Cystic fibrosis (see also: Neonatal cystic fibrosis screening)
• Fatty acid metabolism disorders:
  • Carnitine uptake deficiency
  • Long-chain L-3-hydroxyacyl-CoA dehydrogenase deficiency
  • Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency
  • Trifunctional protein deficiency
  • Very long-chain acyl-CoA dehydrogenase deficiency (VLCAD)
• Galactosemia
• Glucose-6-phosphate dehydrogenase deficiency (G6PD)
• Human immunodeficiency disease (HIV)
• Organic acid metabolism disorders:
  • 3-Hydroxy-3-methylglutaric aciduria (HMG)
  • 3-Methylcrotonyl-CoA carboxylase deficiency (3MCC)
  • Beta ketothiolase deficiency
  • Glutaric acidemia type I
  • Isovaleric acidemia
  • Methylmalonic acidemia
  • Multiple carboxylase deficiency (MCD)
  • Propionic acidemia
• Sickle cell disease and other hemoglobinopathy disorders and traits
• Toxoplasmosis

See also: Hearing loss - infants

Blood tests: A health care professional will prick the baby’s heel to obtain a few drops of blood. The blood is sent to a lab for analysis.

Hearing test: An audiologist will place a tiny earpiece or microphone in the infant’s ear or stick electrodes on the baby’s head.

There is no preparation necessary for newborn screening tests. The tests are performed when the baby is between 24 hours and 7 days old, typically before the baby goes home from the hospital.

The baby will most likely cry when his or her heel is pricked to obtain the small blood sample. The hearing test should not cause the baby to feel pain, cry, or respond.