The Newborn Screen

History of Newborn Screening Began in the 1960s after Dr. Robert Guthrie developed a screening test for phenylketonuria (PKU) using blood samples on filter paper. Since then many metabolic and genetic disorders have been added to state newborn screens, although each state varies in which and how many disorders are screened. MT, SD, and WV only screen for 3 disorders NC and OR screen for 32 and 33 disorders and MS screens for 55 disorders! VA screens for 9 disorders which costs $30 to perform and is charged at $321

Recommendations for NBN screening There is no federal requirement to screen newborns, only recommendations to screen for sickle cell anemia, hypothyroidism, and PKU. The March of Dimes recommends screening for the 9 disorders that VA screens. The Save Babies Through Screening Foundation recommends screening for the 55 disorders MS screens. What is one potential problem associated with increasing numbers of disorders screened?

VA State Requirement for screening Except for an “infant whose parent or guardian objects on the grounds that the testing conflicts with his religious practices or tenets”, every infant in VA is to be screened for 9 metabolic disorders and the physician responsible for newborn care after delivery is responsible for ensuring the NBN screen is performed.3

History of NBN screening in VA 1963 Phenylketonuria 1978 Congenital Hypothyroidism 1984 Maple Syrup Urine Disease Homocystinuria Galactosemia 1986 Biotinidase Deficiency 1989 Sickle Cell Diseases 2002 Congenital Adrenal Hyperplasia 2004 Medium Chain Acyl-CoA Dehydrogenase Deficiency

How and when to screen newborns Blood is to be obtained from the heel and pressed to 4 circles on special filter paper Term infants should have screen performed > 24 hours of age and less than 3 days of life. Preterm infants should have the screen done at 7 days of age or prior to D/C, whichever is first For unattended births, the screen should be performed at the first opportunity after 24 hours of life.

VA Screening Results 2003 100,000 performed with 12,000 repeat screens Disorder Abnl screens Diagnosed cases PKU 18 7 Hypothyroidism 1,646 24 MSUD 19 1 Homocystinuria 25 Galactosemia 295 3 Biotinidase def. 30 Sickle cell 5,489 85 CAH 853 6

The Wonder that is Tandem Mass Spectrometers (MS/MS) Two mass spectrometers in series work within minutes to analyze a blood sample by checking for different types of molecules by weight and the amount of such molecules. Very precise instrument that generates less false positives than previous screening methods. VA purchased three in 2004 at a cost of $850,000 each (needed to test for MCADD).

Factors Affecting Reliability of the Newborn Screen Heat Age Diet Transfusion or dialysis

Phenylketonuria Inherited genetic defect that is autosomal recessive Deficiency or absence of phenylalanine hydroxylase, an enzyme that converts phenylalanine into tyrosine Phenylalanine accumulates in body fluids and damages the CNS Incidence is 1 in 10,000 births

Phenylketonuria Clinical signs: vomiting, feeding difficulty, irritability, eczema, hypopigmented hair and skin, with urine of characteristic odor (by 3 mos age) Treatment is by phenylalanine-restricted diet (special formula for infants) Why we care: Untreated: 95% will have profound mental retardation with an IQ < 50 Treated within first few weeks of life: Normal IQ

Phenylketonuria Infants with classical PKU will have elevated phenylalanine within 4 hours of life, but 24 hours of protein feeding will provide a more accurate screen False positive rate is 1.5%; false negative rate is 0.6%. Children with PKU should also be tested for disorders of tyrosine and biopterin metabolites.

Congenital Hypothyroidism Results in low T4 concentrations from: thyroid agenesis, heterotopic thyroid gland, or disorder of thyroid hormone synthesis Thyroid hormones enhance cell protein and enzyme synthesis important for growth, development, and thermogenesis. Incidence is 1 in 4,000 births with 95% asymptomatic at birth.

Congenital Hypothyroidism Clinical signs with thyroid agenesis: hypertelorism, exophthalmos, protruding tongue, large fontanelles and umbilical hernia Treatment: synthetic T4 (levothyroxine) Why we care: Untreated: mental retardation, developmental delay, constipation, feeding problems, poor growth, hypothermia, hypoactivity Treated: early diagnosis and treatment may prevent MR

Congenital Hypothyroidism Best screened after 24 hours of life, because prior to 24 hours, T4 may be low in normal infants. Not affected by diet. False positive rate of 1.2% and false negative rate of 0.7%.

Maple Syrup Urine Disease Inherited genetic defect that is autosomal recessive. Disorder of branched-chain ketoacid decarboxylation that results in increased levels of leucine, isoleucine, valine, and their corresponding ketoacids Incidence is 1 in 250,000 births

Maple Syrup Urine Disease Clinical signs: poor feeding, vomiting, weight loss, lethargy, abnormal tone, seizures, and loss of reflexes secondary to fulminant ketoacidosis in the first 48-72 hours of life; however, there are milder variants Treatment: dialysis, discontinue protein intake initially; then, a diet limited in branched-chain amino acids and protein with thiamine supplementation (help with dehydrogenase activity) Why we care: Untreated: Death in the first weeks of life Treated: Normal if diagnosed early; later diagnosis with neurologic defects

Maple Syrup Urine Disease Leucine levels rise shortly after birth, but sensitivity for MSUD is after 24 hours of life. False positive rate is 2.4%; false negative rate is 0.7%

Homocystinuria Occurs secondary to one of three enzyme deficiencies in methionine metabolism leading to elevation of homocystine Incidence is 1 in 200,000 births Type I (cystathione synthase deficiency) infants are normal at birth, then may show developmental delay and failure to thrive Diagnosis is usually made after 3 yrs of age when subluxation of the lens occur. What other disorder will you see ectopia lentis? Progressive mental retardation often occurs, psychiatric disorders are common, 20% will have seizures, phenotypically they have long arms and fingers, scoliosis, sternal deformities, fair skin and blue eyes with a malar flush. They have osteoporosis and increased risk for thromboembolic events. Lab studies reveal homocystinuria and elevated methionine. Treatment is with high doses of B6, often in conjunction with folic acid, restriction of methionine intake, and cysteine supplementation

Homocystinuria Type II (defects in methylcobalamin formation) infants will demonstrate poor feeding, vomiting, lethargy, hypotonia, and developmental delay in the first few months Lab studies will reveal homocystinuria, hypomethionemia, and megaloblastic anemia Treatment is with vitamin B12 Type III (methylenetetrahydrofolate reductase deficiency) infants can develop apneic episodes and myoclonic seizures that can lead rapidly to coma and death in the neonatal period for complete absence of the enzyme Lab studies reveal homocystinuria and low to normal methionine levels Treatment has been tried with folic acid, B6, B12, methionine supplementation, and betaine. Betaine, a methyl group donor (remethylates homocysteine to methionine) is the only one that has been proven helpful.

Homocystinuria Accurate screening requires adequate protein ingestion; test best done after 48 hours of life. False positive rate is 0%; false negative rate is 3.3%.

Galactosemia Inherited genetic defect that is autosomal recessive. Many types, but most common is a deficiency of galactose-1-phosphate uridyltransferase. This enzyme allows galactose to be converted into glucose in the digestion of lactose (milk sugar). Incidence is 1 in 60,000 births

Galactosemia Clinical signs: IUGR, vomiting and diarrhea with lactose feeds, hypoglycemia, E. coli sepsis, hepatic damage with secondary hyperbilirubinemia, hepatomegaly, and cirrhosis, cataract development by 3 months of age Treatment: dietary restriction of lactose, watch carefully for signs of sepsis Why we care: Untreated: Usually death; survivors will have severe MR, CP, cataracts, and liver disease Treated: Normal intelligent with early diagnosis and treatment, but many have developmental and learning disabilities despite treatment with a high incidence of secondary ovarian failure in females.

Galactosemia If screening test is determining enzyme activity, screen is valid at any time; if screen is measuring galactose levels, adequate lactose ingestion is necessary False positive rate is 0.6%; false negative rate is 0%.

Biotinidase Deficiency Biotin is a vitamin that acts as a cofactor for all carboxylase activity in the body. Carboxylases aid in fatty acid synthesis, amino acid digestion, and gluconeogenesis. Biotinidase is an enzyme that releases free biotin from protein in the intestines. This disorder is inherited in an autosomal recessive manner. Incidence is 1 in 100,000.

Biotinidase Deficiency Hearing loss, vision loss, and developmental delay can still persist in symptomatic children, but often marked improvement is often seen after administering biotin. Screen is not dependent on feeding or age to be accurate. False positive rate is 0.4%; false negative rate is 2.1%.

Biotinidase Deficiency Clinical signs: onset between 2 weeks and 3 yrs of age; tachypnea (why?), apnea, hypotonia, myoclonic seizures, vomiting, failure to thrive, erythematous rash, alopecia, developmental delay, optic atrophy, immunologic problems, and stinky pee (like which animal?) Lab findings: metabolic acidosis, ketosis, multiple organic acidemia Treatment: biotin (10mg/24 hours); only $100 per year

Sickle cell diseases, CAH, and MCADD All for another lecture!