Spring 2002 Volume Five Number Two

• The Newborn Screen: Why Are You Poking My Baby’s Heel?
—Infant newborn screening revised.

Have you ever wondered what that heel- poke blood test is? Every baby born in Minnesota must have one after he or she is 24-hours old, and most have the test done before being discharged from the newborn nursery.

The newborn screen is a wonderful example of the public health system and modern medicine at work. A tiny blood sample is squeezed from the baby’s heel onto filter paper, air dried and sent to the Minnesota Department of Health, where it is analyzed for 24 rare but treatable diseases.

In most cases, these diseases would lead to mental retardation or death if not detected and treated early. All state health departments operate these programs, but there are variations from state to state, just as there are in vaccine programs and in how epidemics are handled.

How do we decide what diseases to screen for? One criterion is that the diseases need to be detectable at birth, with early diagnosis affecting outcome. The diseases need to be treatable. In addition, the screening needs to be reliable, inexpensive and easy to perform.

Minnesota began to perform newborn screens in 1964 with only one disease (PKU, or phenylketonuria). Subsequently, hypothyroidism (the severe type that can affect newborns), galactosemia, sickle cell disease and congenital adrenal hyperplasia were added to the list.

In 2001, new advanced technology (tandem mass spectrometry), led to the addition of 19 new diseases to the program. The new diseases added to the list have even longer and more complicated names than the ones already mentioned. They fall into three categories: disorders of amino acid metabolism; disorders of organic acid metabolism and disorders of fatty acid oxidation.

The table below gives information about these disorders and their treatments. Most of the diseases require a very specialized diet to prevent build-up of toxic substances that an affected individual cannot metabolize properly.
Some of the diseases require special vitamins and a few require medication, such as hormone replacement (for example, hypothyroidism requires thyroid hormone replacement).

One thing to remember is that these tests are screens. This means that they are very sensitive in detecting the diseases in question. It also means that they are sometimes too sensitive, and a positive test does not necessarily mean that the baby has the disease. A positive test means that further blood will need to be obtained to confirm the possible diagnosis.

The Department of Health has a very good method for informing us if your baby’s screen is positive. Then we arrange for further testing.

We should have the results in about two weeks and if they are not back by then, we have staff members at each office whose job it is to track them down. As you can see from the table below, we don’t test for these diseases because they are so common, we test for them because they are treatable if caught early.

For more information, the Minnesota Department of Health has the following web site: www.health.state.mn.us/divs/fh/mcshn/nbshome.htm

—Jane Laco, MD