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  Last Updated on 07/13/2018

Newborn Screening Tests


from kidshealth.org


Newborn screening is the practice of testing every newborn for certain harmful or potentially fatal disorders that are not otherwise apparent at birth. Many of these are metabolic disorders, often called "inborn errors of metabolism," which interfere with the body's use of nutrients to maintain healthy tissues and produce energy. Other disorders that may be detected through screening include problems with hormones, vitamin levels, 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 could eventually cause problems. Even though 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.


Newborn Screening: Past, Present, and Future
In the early 1960s, scientist Robert Guthrie, PhD, developed a blood test that could determine whether newborn babies had a metabolic disorder known as phenylketonuria (PKU). People with PKU lack an enzyme needed to process the amino acid phenylalanine. This amino acid is necessary for normal growth in infants and children and for normal protein use throughout life. However, if too much of it builds up, it damages the brain tissue and can eventually cause mental retardation.


When babies with PKU are put on a special diet right away, they often can avoid the mental retardation that children with PKU suffered in the past. By following certain dietary restrictions, these children can 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, mental retardation, and in some cases, death. All states, the District of Columbia, Puerto Rico, and the U.S. Virgin Islands now have their own mandatory newborn screening programs. Because the federal government has set no national standard, screening requirements vary from state to state, as determined by individual state public health departments.


Consequently, the comprehensiveness of these programs varies, with states routinely screening for anywhere from four to 30 disorders. The average state program tests from four to 10 disorders.


State requirements tend to change periodically as well. In fact, the pace of change is speeding up, thanks to the development of a new screening technique known as tandem mass spectrometry. This technology, which can detect the blood components that are elevated in certain disorders, is capable of screening for more than 20 inherited metabolic disorders with a single test.


Some states are already offering expanded screening with tandem mass spectrometry through pilot studies. However, there's some controversy over whether the new technology has been tested adequately. Also, some experts want more evidence that early detection of every disease tested for will actually offer babies some long-term benefit; equally important, parents may not want to know ahead of time that their child will develop a serious condition when there are no medical treatments or dietary changes that can improve the outcome. And some questions about who will pay (states, insurance companies, or parents) for the newer technology have yet to be resolved.


The American Academy of Pediatrics (AAP) and the federal government's Health Resources and Services Administration convened a task force of experts to grapple with these issues and recommend next steps. Their report identified some flaws and inconsistencies in the current state-driven screening system and proposed the following:


  • All state screening programs should reflect current technology.

  • All states should test for the same disorders.

  • Parents should be informed about screening procedures and have the right to refuse screening, as well as the right to keep the results private and confidential.

  • Parents should be informed about the benefits and risks associated with newborn screening.


All of this can be a little confusing (and anxiety-provoking!) for a new parent. The inconsistencies among state requirements mean that there's no clear consensus on what's really necessary. On the one hand, it's important to keep in mind that the disorders being screened for are rare. On the other hand, no parent wants to take any unnecessary chances with the quality of his or her child's life - no matter how small the risk.


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 undue anxiety they cause)

  • the availability of treatments proven to help the condition

  • financial costs


And states often face conflicting priorities when determining their budgets. For instance, a state may face a choice between expanding newborn screening and ensuring that all expectant mothers get sufficient prenatal care. Of course, this offers little comfort to parents whose children have a disorder that could have been found through a screening test but wasn't.


So what can you do? Your best strategy is to stay informed. Discuss this issue with both your obstetrician 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 is required by state law). You may also want to ask your doctors about supplemental screening - keep in mind, though, that you'll probably have to pay for additional tests out of your own pocket.


If you're the parent of an infant and are concerned about whether your child was screened for certain conditions, ask your child's doctor for information about which tests were performed and whether further tests are recommended.


What Disorders Will Be Screened for in My Newborn?
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 and are listed in order from the most common (all states screen for the first two) to least common (ranging from three-fourths or one-half of states to just a few). Incidence figures included in this list are according to a 1996 AAP policy statement.


  • PKU: 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.

  • galactosemia: 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.

  • sickle cell disease: Sickle cell disease is an inherited blood disease in which red blood cells stretch 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 Hispanic, Mediterranean, Middle Eastern, and South Asian descent.

  • biotinidase deficiency: Babies with this condition don't have enough biotinidase, an enzyme that recycles biotin (one of the B vitamins) 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 these are not processed properly, they 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 these outcomes. 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.

  • homocystinuria: This metabolic disorder results from a deficiency of one of several enzymes needed by the brain for normal development. If untreated, it can lead to dislocated lenses of the eyes, mental retardation, skeletal abnormalities, and abnormal blood clotting. However, a special diet combined with dietary supplements may help prevent most of these problems. Incidence: 1 in 50,000 to 150,000.

  • tyrosinemia: Babies with this 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. A special diet and sometimes a liver transplant are needed to treat the condition. Early diagnosis and treatment seem to offset long-term problems, although more information is needed. Incidence: not yet determined.

  • cystic fibrosis: Cystic fibrosis is an inherited disorder of the various organs that causes cells to release a thick mucus, which can lead to chronic respiratory disease, problems with digestion, and poor growth. There is no known cure - treatment involves trying to prevent the serious lung infections associated with it and providing adequate nutrition. Some infections may be prevented with antibiotics. Detecting the disease early may help doctors reduce the lung and nutritional problems associated with cystic fibrosis, but the real impact of newborn screening is yet to be determined. Incidence: 1 in 2,000 Caucasian babies; less common in African-Americans, Hispanics, and Asians.

  • toxoplasmosis: Toxoplasmosis is a parasitic infection that can be transmitted through the mother's placenta to an unborn child. The disease-causing organism, which is found in uncooked or undercooked meat, can invade the brain, eye, and muscle, possibly resulting in blindness and mental retardation. The benefit of early detection and treatment is uncertain. Incidence: 1 in 1,000.


These are not the only disorders that can be detected through newborn screening. Certain other rare disorders of body chemistry can also be detected. Other conditions that are candidates for newborn screening include Duchenne muscular dystrophy, a childhood form of muscular dystrophy that can be detected through a blood test; HIV; and neuroblastoma, a type of cancer that can be detected with a urine test.


Should I Request Additional Tests?


  • Do you have a positive family history of an inherited disorder?

  • Have you previously given birth to a child who is 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?


If you answered yes to any of the above questions, talk to your child's future doctor and perhaps a genetic counselor about requesting additional tests.


If your hospital can't or won't make expanded screening available to you, and your doctors believe additional testing would be worthwhile, you may want to contact outside laboratory services that provide supplemental testing for more than 30 metabolic disorders through a mail-order service available anywhere in the United States. The labs send out kits that are used to collect additional blood at the time of your baby's regular screening, and this sample is then mailed back for analysis. The cost ranges from $25 to $50.


How Is Newborn Screening Performed?
Within the first 2 or 3 days of life, your baby's heel will be pricked and a small sample of her blood will then be applied to a card. Most states have identified a state or regional laboratory to which hospitals should send the samples for analysis. (If your hospital offers expanded screening that uses the new technology, your baby's sample may be sent to a private laboratory.)


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 are 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, the AAP recommends 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.


Getting the Results
Different labs have different procedures for sending the results. Some may send them 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 child's doctor how you will get the results and when you should expect them.


If a test result should come 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 child's 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, can often avert most of the serious physical and mental problems that were associated with metabolic disorders in the past.


You may also wonder whether the disorder can be passed on to any future children. This is a matter you'll want to discuss with your child's doctor and perhaps a genetic counselor. Also, if you have other children who were not screened for the disorder, you may want to have this done. Again, talk this over with your children's doctor.


Additional Information
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 child's doctor or contact your state's department of health for more information.





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