Questions about newborn screening are frequent. In the last 50 years the number of genetic tests which can be performed on a newborn have increased from one to over 60. Not every state requires all the tests. The tests are determined by the State’s Department of Health. Fortunately as the ease of completing the analysis has risen and the cost has decreased, each state has added more testing.
Why are these tests done in the first place? Every test result is linked to a disease and every disease can have a widespread effect on the child, the family and the medical handling of the child.
In the 1960’s Dr. Robert Guthrie developed a test for phenylketonuria (PKU). This first test involved analyzing a few drops of blood from a heel stick placed on filter paper. At first this was done a few hours after birth. But with time it was discovered that if the newborn was at least 12 hours old and preferably over 24 hours old the result was more accurate. PKU affects about 1/16,000 newborns in the U.S. alone. The elimination of phenylalanine in the diet starting as soon as possible prevents the newborn from developing growth and nervous system problems.
Hypothyroidism is another early test developed using the same filter paper method. This test goes through several stages of analysis. When the results are finalized, the number of true hypothyroid newborns is 1/4000 worldwide. The consequences of non-treatment are devastating. There is failure to grow, decreased activity, tongue enlargement, and mental retardation if treatment is not initiated in the first few weeks after birth.
Galactosemia is a serious disease due to the inability of the newborn to breakdown the lactose in breast milk and many formulas into usable products. The incidence is 1/60,000 newborns. These infants have problems with low blood glucose which can result in seizures. They don’t grow well, are retarded and usually have liver and kidney problems. Newborn screening can identify this deficiency and the infant’s diet can be changed to lactose-free.
Around the late 1990s, the number of tests increased. A test for hemoglobin type began in the early 2000s which has been of great help in identifying hemoglobinopathies. Treatment for Thallasemia and Sickle Cell Anemia can be recognized early and a treatment plan developed.
Most states have now added cystic fibrosis (1/7500) which is a major cause of severe lung disease in children. With newer methods of analysis, the various mutations of this gene which determines the severity of disease in the child can be determined. There are medication and therapeutic interventions when if started early can aid cystic fibrosis patients to grow and function almost normally.
Other tests on the screen deal with inborn errors of metabolism including a long list of amino acid, organic acid and fatty acids necessary for normal bodily function and growth. Most of these defects need to be discovered early of they may be fatal.
Additional information is available from the National Newborn Screening and Genetics Resource Center (nnsis.uthscsa.edu) or any search engine on your computer.
By Bruce Gach, M.D.
Bruce is the managing partner of Livermore-Pleasanton-San Ramon Pediatrics Group. He is a Board Certified practicing pediatrician with over 30 years of experience caring for children. He has served on numerous committees dealing with child health and development. www.livermorepleasantonpeds.com