Newborn Screening Tests

Newborn Screening Tests

When infants are just days old, they have blood drawn for newborn screening tests to detect the presence of endocrine (hormonal), metabolic or hematological (blood related) disorders that could cause severe developmental damage or death. The tests are done early to identify the disorders and begin treatment before symptoms occur.

There are roughly 30 newborn screening tests that can be done. Each state follows different guidelines for newborn screening so the actual tests done on your child depend on the state in which you reside. Here are some of the more common tests that are run.

Phenylketonuria (PKU) – A rare autosomal recessive disorder (both parents must pass on the defective gene for the child to be affected). The amino acid phenylalanine is not properly metabolized because of the missing enzyme phenylalanine hydroxylase. Untreated, PKU causes brain damage resulting in severe mental retardation. Affected individuals must follow a strict diet extremely low in phenylalanine commonly found in milk, eggs and many other protein rich foods and in NutraSweet (aspartame). Close supervision by a physician or dietician is recommended.

Congenital Adrenal Hyperplasia (CAH) – Actually a group of endocrine disorders, CAH is the body’s inability to produce enough cortisol, an adrenal hormone. The body tries to compensate by producing more of other hormones. The particular hormone imbalances determine which type of CAH is present. The affected individual may have impaired development or difficulty healing from disease or injury. It is inherited as an autosomal recessive trait.

Treatment consists of hormone replacement to restore and maintain the physiologic balance to the endocrine system. Careful monitoring of hormone levels, development and response to illness and injury are essential.

Sickle Cell Anemia – Sickle cell anemia is a blood disorder prevalent among people of African and Mediterranean descent. It exists when hemoglobin, the oxygen-carrying molecule in blood, deforms into sickle shaped crystals and is unable to transport adequate amounts of oxygen to cells. The malformed, deoxygenated molecules cause blood clots leading to strokes, joint pain and damage to internal organs. There is no cure for sickle cell anemia. Treatment is aimed at reducing pain and preventing the potentially deadly complications. Sickle Cell Anemia is an autosomal recessive trait. A newborn with one abnormal hemoglobin S chain and one normal Hemoglobin chain is said to be a carrier and may exhibit few if any symptoms.

Congenital Hypothyroidism – Congenital hypothyroidism results in babies who are unable to produce adequate amounts of thyroid hormone. The most common causes are total or partial failure of the thyroid gland to develop or its development in an abnormal location. These types of hypothyroidism rarely recur in siblings.

Thyroid hormone is essential for normal growth and development, especially for normal brain growth. If untreated, congenital hypothyroidism results in mental retardation and stunted growth. Thyroid hormone replacement is easily given to infants in their food. The child must have regular follow up with an endocrinologist to monitor growth and to adjust medication dosages accordingly.

Galactosemia – Galactosemia, another autosomal recessive trait, develops when an infant is lacking enzymes necessary to metabolize galactose a major sugar of milk.

The baby appears normal at birth, but develops vomiting, diarrhea, lethargy, jaundice, and liver damage when milk-feedings are initiated. Left untreated, the disorder may result in death. Infants who survive may demonstrate developmental retardation, enlarged livers, kidney malfunction, growth failure and cataracts. These children must avoid all lactose and galactose containing foods. Consultation with a pediatric metabolic specialist is recommended.

Cystic Fibrosis – Cystic fibrosis is an inherited disease of the mucus glands that affects many body systems. The disorder’s most common signs and symptoms include progressive damage to the respiratory system and chronic digestive system problems. Most people with cystic fibrosis also have digestive problems because thick, sticky mucus interferes with the function of the pancreas. The pancreas is an organ that produces insulin (a hormone that helps control blood sugar levels). It also makes enzymes that help digest food. In people with cystic fibrosis, mucus blocks the ducts of the pancreas, preventing these enzymes from reaching the intestines to aid digestion. Problems with digestion can lead to diarrhea, malnutrition, poor growth, and weight loss. Some babies with cystic fibrosis have meconium ileus, a blockage of the intestine that occurs shortly after birth. Cystic Fibrosis occurs in 1 in 2,500 to 3,500 Caucasian newborns. Cystic fibrosis is less common in other ethnic groups. Cystic Fibrosis is inherited as an autosomal recessive disease, so a person has to have defective genes from both parents in order to develop the disease. (Compiled from Genetic’s Home Reference)

Most diseases detectable by newborn screening tests are easily treated with specialized diets or with medications.

So what are parents to do? Avis Meeks Day, M.D., a pediatrician at the Austin Regional Clinic in Austin, Texas says,

“Parents should obtain a good family history. If a close relative (a parent, sibling or close cousin) has a congenital disorder or had an infant with a congenital disorder, more screenings or actual definitive testing for specific disorders should be obtained.”

Pediatricians are on the front lines of diagnosing and treating these disorders and bear the brunt of parents’ anger and frustration when there is an adverse outcome.

“Sure the disorders are rare, say 1/50,000. But the odds don’t matter when it’s your child with a disorder that could have been avoided if we knew sooner to alter his diet or add a daily medication.”

Day says that parents have the option of requesting additional screening tests. There are private laboratories that run a wider array of newborn screening tests. Additional screening tests aren’t covered by insurance and require private payment. Check your local department of health and human services to see which screening tests are run in your area.

Resources

Save Babies Through Screening Foundationwww.savebabies.org.

Benefit Analysis of Universal Tandem Mass Spectrometry for Newborn Screening Schoen, E. et al, Pediatrics 2002; 110 781-786. Cost

The American Academy of Pediatrics www.aap.org

The March of Dimes

The National Newborn Screening and Genetic Resource Site