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Testing for Disorders at Birth.

Newborn screening--testing infants for certain genetic anomalies, inborn errors of metabolism, and other disorders--has been commonplace since the 1960s but has rarely been a topic for public discourse. Within the last year or two, though, newborn screening has become of interest not only to healthcare professionals and scientific researchers, but to a far broader audience.

Articles in such publications as the Philadelphia Enquirer, US News and World Report, and The New York Times have explored the subject of screening. The Morbidity and Mortality Weekly Report, a publication of the Atlanta-based Centers for Disease Control and Prevention, reported on data from Georgia's screening program. The Maternal and Child Health Bureau (part of the federal Health Resources and Services Administration) and the American Academy of Pediatrics (AAP) have convened a task force on newborn screening to update the AAP's 1996 guidelines. The initial report is expected within the next few months. Many state legislatures are reexamining their current programs and debating expansion of testing requirements. The almost-complete Human Genome Project is expected to prompt still further discussion of issues surrounding testing for errors of metabolism and genetic disorders.

In this three-part Special Report, EP will explore newborn screening and its ramifications. We begin this month with an overview of newborn screening: history, the state of the art, and brief descriptions of the most commonly tested disorders in the United States today.

OVERVIEW

In 1963, Massachusetts became the first state to mandate screening for a genetic disorder. A test developed in 1961 by Dr. Robert Guthrie of the University of Buffalo identified phenylketonuria (PKU)(*), an inherited condition that, if left untreated, causes severe mental retardation. The National Association for Retarded Children, the Children's Bureau, and the Kennedy Foundation were among the organizations that pushed for widespread adoption of the Guthrie test for PKU, which is now mandated by all 50 states and the District of Columbia.

Dr. Guthrie's work in the field of mental retardation led him to develop tests for galactosemia, maple syrup urine disease (MSUD), and homocystinuria. Ongoing research in disciplines including cell biology, biochemistry, enzymology and genetics (aided by increasing sophistication of techniques such as electron microscopy, chromatography, and spectrophotometry) enabled development of tests for congenital hypothyroidism, biotinidase deficiency, congenital adrenal hyperplasia, and hemoglobinopathies such as sickle cell disease. Screening for hypothyroidism, like PKU, is now mandated throughout the US, and the test for galactosemia is required everywhere but Louisiana, Pennsylvania, and Washington state. Tests for other disorders--cystic fibrosis, tyrosinemia, toxoplasmosis, MCAD, G6PD, and HIV--are required by only a few states. (The accompanying Table displays mandatory newborn screens by state, plus some tests performed by special request only, which are marked "SR.")

WHY SCREENINGS HAVE NOT ALWAYS BEEN PERFORMED

Although it would seem logical to screen all newborns for every possible disorder, there are several reasons why this has not been so.

1. Problems with testing methodology. The Guthrie test, based on a blood spot on filter paper from a heelstick (a method of obtaining blood samples from newborns by pricking the heel) and bacterial assays (tests), required a separate test for each disorder although the same blood spot could be used. Results were generally not available prior to the infant's discharge from the hospital. Some conditions, such as hypothyroidism, initially required urine samples to be tested through chromatography, and it was found that specimens needed to be collected seven or more days after birth to give true readings. There was often considerable difficulty in obtaining samples for tests because most newborns were no longer in the hospital.

2. Difficulty providing necessary follow-up and counseling. Many conditions required long-term monitoring, follow-up testing, and parental counseling. The frequency with which many families change residences and insufficient manpower at medical facilities made it difficult to track and counsel families, secure specimens for follow-up tests and monitor treatment. If the child was asymptomatic, parents could be resistant to counseling, ongoing tests, and perceived "interference" from the state.

3. No available treatment. Because none of these conditions is curable, they might not be screened for. Some, such as PKU, are treatable with highly restrictive diets; others, such as HIV, require exacting and expensive drug regimens. Support, both emotional and financial, can be problematic.

4. Limited resources. Some states perform all tests in state laboratories; in others, some tests might be referred to private labs. Smaller states have created regional coalitions for testing of some disorders. Cost of testing is an ongoing issue; if each disorder requires a separate test, lab fees can add up quickly. Responsibility for payment and allocating costs has only become more complicated by managed care. Staffing needs, both for labs and for counseling and follow-up, grow as tests' are added, requiring higher payrolls.

5. Rarity of disease. Incidence of these conditions might range from 1:1,400 (hemoglobinopathies) to 1:150,000 (homocystinuria) live births, and might further vary by race and ethnicity. State population and demographics might suggest that routine screening for some disorders would be unproductive.

A BRIGHTER HORIZON

Several of the reasons for limits on mandated screening will, in some form, always remain part of the debate. A radical change in treatment methodology, however, is redefining one argument, changing the terms of others, and fostering reexamination of newborn screening.

Tandem mass spectrometry (MS/MS) is a powerful and extremely sensitive testing tool, with the ability to use one test for many disorders. MS/MS can identify approximately 30 different conditions from one or two heelsticks performed within 24 hours of birth, and reduces the rate of false-positive results seen with traditional testing methodologies from about 1.5 percent to about 0.26 percent. However, the equipment is costly and highly specialized training is required to read test results. There are only a few MS/MS facilities in the US.

[TABULAR DATA NOT REPRODUCIBLE IN ASCII]

(*) See glossary for boldface words.

Next month's article will cover the medical aspects of screening in greater detail, including sources for performing tests, disorders that can be identified through screening, and types of treatment available for various groups of disorders. In October, look for coverage of other aspects of screening, including privacy concerns, public-health questions, and economic implications.
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Article Details
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Author:Potvin, Fern R.
Publication:The Exceptional Parent
Date:Aug 1, 2000
Words:1026
Previous Article:familiar faces.
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