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Medical Care & Your Baby

Newborn Screening Tests

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About Newborn Screening

Newborn screening is the practice of testing every newborn for certain harmful or potentially fatal disorders that aren’t otherwise apparent at birth.

Many of these are metabolic disorders (often called “inborn errors of metabolism”) that interfere with the body’s use of nutrients to maintain healthy tissues and produce energy. Other disorders that screening can detect include problems with hormones or the blood.

In general, metabolic and other inherited disorders can hinder an infant’s normal physical and mental development in a variety of ways. And parents can pass along the gene for a certain disorder without even knowing that they’re carriers.

With a simple blood test, doctors often can tell whether newborns have certain conditions that eventually could cause problems. Although these conditions are considered rare and most babies are given a clean bill of health, early diagnosis and proper treatment can make the difference between lifelong impairment and healthy development.

Screening: Past, Present & Future

In the early 1960s, scientist Robert Guthrie, PhD, developed a blood test that could determine whether newborns had the metabolic disorder phenylketonuria (PKU). People with PKU lack an enzyme needed to process the amino acid phenylalanine, which is necessary for normal growth in kids and for normal protein use throughout life. However, if too much phenylalanine builds up, it damages brain tissue and eventually can cause substantial developmental delay.

If kids born with PKU are put on a special diet right away, they can avoid the developmental delay the condition caused in past generations and lead normal lives.

Since the development of the PKU test, researchers have developed additional blood tests that can screen newborns for other disorders that, unless detected and treated early, can cause physical problems, developmental delay, and in some cases, death.

The federal government has set no national standards, so screening requirements vary from state to state and are determined by individual state public health departments. Many states have mandatory newborn screening programs, but parents can refuse the testing for their infant if they choose.

Almost all states now screen for more than 30 disorders. One screening technique, the tandem mass spectrometry (or MS/MS), can screen for more than 20 inherited metabolic disorders with a single drop of blood.

Which Tests Are Offered?

Traditionally, state decisions about what to screen for have been based on weighing the costs against the benefits. “Cost” considerations include:

  • the risk of false positive results (and the worry they cause)
  • the availability of treatments known to help the condition
  • financial costs

So what can you do? Your best strategy is to stay informed. Discuss this issue with both your obstetrician or health care provider and your future baby’s doctor before you give birth. Know what tests are routinely done in your state and in the hospital where you’ll deliver (some hospitals go beyond what’s required by state law).

If your state isn’t offering screening for the expanded panel of disorders, you may want to ask your doctors about supplemental screening, though you’ll probably have to pay for additional tests yourself.

If you’re concerned about whether your infant was screened for certain conditions, ask your child’s doctor for information about which tests were done and whether further tests are recommended.

Newborn screening varies by state and is subject to change, especially given advancements in technology. However, the disorders listed here are the ones typically included in newborn screening programs.


When this disorder is detected early, feeding an infant a special formula low in phenylalanine can prevent mental retardation. A low-phenylalanine diet will need to be followed throughout childhood and adolescence and perhaps into adult life. This diet cuts out all high-protein foods, so people with PKU often need to take a special artificial formula as a nutritional substitute. Incidence: 1 in 10,000 to 25,000.

Congenital Hypothyroidism

This is the disorder most commonly identified by routine screening. Affected babies don’t have enough thyroid hormone and so develop retarded growth and brain development. (The thyroid, a gland at the front of the neck, releases chemical substances that control metabolism and growth.)

If the disorder is detected early, a baby can be treated with oral doses of thyroid hormone to permit normal development. Incidence: 1 in 4,000.


Babies with galactosemia lack the enzyme that converts galactose (one of two sugars found in lactose) into glucose, a sugar the body is able to use. As a result, milk (including breast milk) and other dairy products must be eliminated from the diet. Otherwise, galactose can build up in the system and damage the body’s cells and organs, leading to blindness, severe mental retardation, growth deficiency, and even death.

Incidence: 1 in 60,000 to 80,000. Several less severe forms of galactosemia that may be detected by newborn screening may not require any intervention.

Sickle Cell Disease

Sickle cell disease is an inherited blood disease in which red blood cells mutate into abnormal “sickle” shapes and can cause episodes of pain, damage to vital organs such as the lungs and kidneys, and even death. Young children with sickle cell disease are especially prone to certain dangerous bacterial infections, such as pneumonia (inflammation of the lungs) and meningitis (inflammation of the brain and spinal cord).

Studies suggest that newborn screening can alert doctors to begin antibiotic treatment before infections occur and to monitor symptoms of possible worsening more closely. The screening test can also detect other disorders affecting hemoglobin (the oxygen-carrying substance in the blood).

Incidence: about 1 in every 500 African-American births and 1 in every 1,000 to 1,400 Hispanic-American births; also occurs with some frequency among people of Mediterranean, Middle Eastern, and South Asian descent.

Biotinidase Deficiency

Babies with this condition don’t have enough biotinidase, an enzyme that recycles biotin (a B vitamin) in the body. The deficiency may cause seizures, poor muscle control, immune system impairment, hearing loss, mental retardation, coma, and even death. If the deficiency is detected in time, however, problems can be prevented by giving the baby extra biotin. Incidence: 1 in 72,000 to 126,000.

Congenital Adrenal Hyperplasia

This is actually a group of disorders involving a deficiency of certain hormones produced by the adrenal gland. It can affect the development of the genitals and may cause death due to loss of salt from the kidneys. Lifelong treatment through supplementation of the missing hormones manages the condition. Incidence: 1 in 12,000.

Maple Syrup Urine Disease (MSUD)

Babies with MSUD are missing an enzyme needed to process three amino acids that are essential for the body’s normal growth. When not processed properly, these can build up in the body, causing urine to smell like maple syrup or sweet, burnt sugar. These babies usually have little appetite and are extremely irritable.

If not detected and treated early, MSUD can cause mental retardation, physical disability, and even death. A carefully controlled diet that cuts out certain high-protein foods containing those amino acids can prevent this. Like people with PKU, those with MSUD are often given a formula that supplies the necessary nutrients missed in the special diet they must follow. Incidence: 1 in 250,000.


Babies with this amino acid metabolism disorder have trouble processing the amino acid tyrosine. If it accumulates in the body, it can cause mild retardation, language skill difficulties, liver problems, and even death from liver failure. Treatment requires a special diet and sometimes a liver transplant. Early diagnosis and treatment seem to offset long-term problems, although more information is needed. Incidence: not yet determined. Some babies have a mild self-limited form of tyrosinemia.

Cystic Fibrosis

Cystic fibrosis (CF) is a genetic disorder that particularly affects the lungs and digestive system and makes kids who have it more vulnerable to repeated lung infections. There is no known cure — treatment involves trying to prevent serious lung infections (sometimes with antibiotics) and providing adequate nutrition. Early detection may help doctors reduce the problems associated with CF, but the real impact of newborn screening has yet to be determined. Incidence: 1 in 2,000 Caucasian babies; less common in African-Americans, Hispanics, and Asians.

MCAD Deficiency

MCAD (medium chain acyl CoA dehydrogenase) deficiency is a fatty acid metabolism disorder. Kids who have it are prone to repeated episodes of low blood sugar (hypoglycemia), which can cause seizures and interfere with normal growth and development. Treatment involves making sure kids don’t fast (skip meals) and supplies extra nutrition (usually by intravenous nutrients) when they’re ill. Early detection and treatment can help affected children live normal lives.


Toxoplasmosis is a parasitic infection that can be transmitted through the mother’s placenta to an unborn child. The disease-causing organism can invade the brain, eye, and muscles, possibly resulting in blindness and mental retardation. The benefit of early detection and treatment is uncertain. Incidence: 1 in 1,000. But only one or two states screen for toxoplasmosis.

Hearing Screening

Most but not all states require newborns’ hearing to be screened before they’re discharged from the hospital. If your baby isn’t examined then, be sure that he or she does get screened within the first 3 weeks of life.

Kids develop critical speaking and language skills in their first few years. A hearing loss that’s caught early can be treated to help prevent interference with that development.

Should I Request Additional Tests?

If you answer “yes” to any of these questions, talk to your doctor and perhaps a genetic counselor about additional tests:

  • Do you have a family history of an inherited disorder?
  • Have you previously given birth to a child who’s affected by a disorder?
  • Did an infant in your family die because of a suspected metabolic disorder?
  • Do you have another reason to believe that your child may be at risk for a certain condition?

How Screening Is Done

In the first 2 or 3 days of life, your baby’s heel will be pricked to obtain a small blood sample for testing. Most states have a state or regional laboratory perform the analyses, although some use a private lab.

It’s generally recommended that the sample be taken after the first 24 hours of life. Some tests, such as the one for PKU, may not be as sensitive if they’re done too soon after birth. However, because mothers and newborns are often discharged within a day, some babies may be tested within the first 24 hours. If this happens, experts recommend that a repeat sample be taken no more than 1 to 2 weeks later. It’s especially important that the PKU screening test be run again for accurate results. Some states routinely do two tests on all infants.

Getting the Results

Different labs have different procedures for notifying families and pediatricians of the results. Some may send the results to the hospital where your child was born and not directly to your child’s doctor, which may mean a delay in getting the results to you.

And although some states have a system that allows doctors to access the results via phone or computer, others may not. Ask your doctor how you’ll get the results and when you should expect them.

If a test result comes back abnormal, try not to panic. This does not necessarily mean that your child has the disorder in question. A screening test is not the same as diagnostic test. The initial screening provides only preliminary information that must be followed up with more specific diagnostic testing.

If testing confirms that your child does have a disorder, your doctor may refer you to a specialist for further evaluation and treatment. Keep in mind that dietary restrictions and supplements, along with proper medical supervision, often can prevent most of the serious physical and mental problems that were associated with metabolic disorders in the past.

You also may wonder whether the disorder can be passed on to any future children. You’ll want to discuss this with your doctor and perhaps a genetic counselor. Also, if you have other children who weren’t screened for the disorder, consider having testing done. Again, speak with your doctor.

Know Your Options

Because state programs are subject to change, you’ll want to find up-to-date information about your state’s (and individual hospital’s) program. Talk to your doctor or contact your state’s department of health for more information.

Reviewed by: Patricia G. Wheeler, MD
Date reviewed: September 2012