Your Children's Health

By Roy Benaroch, MD

Everyone is terrified of getting bad news from the doctor: “Unfortunately, the tests show …” may be among the most frightening words a patient ever has to hear. But many tests are just screening tests, and I fear that sometimes they create far more worry than is really justified. Doctors might not be doing a good job explaining exactly what a screening test is, and why a failed screen does not mean that you really need to worry.

Some tests are done to confirm a diagnosis. They’re very accurate—if you test HIV positive, for instance, that’s a result that is dependable and correct. But many of the tests routinely done in medicine are screening tests, done widely on a population. These aren’t done to make definite diagnoses; they’re done to find out who’s at higher risk of a health problem so those people can have more-definitive tests done. Most people who “fail” a screening test don’t in fact have any sort of disease. They just need more tests to know for sure.

An example: many women are offered screening for Down Syndrome and other genetic problems during pregnancy. There are different ways to do this using blood tests or ultrasounds or a combination of the two, but the bottom line is that most pregnant women who “fail” the initial screen do not have a baby with Down Syndrome. The screening test isn’t meant to make a certain diagnosis, it’s just meant to see who needs the more intense and more expensive next level of screening. If a pregnant woman “fails” the screen for Down Syndrome, but the amniocentesis is normal, her baby absolutely does not have Down Syndrome.

Several important screening tests are done on newborn babies. The first hearing screen, for instance, is important because it picks up babies who are at risk for hearing problems, so they can get more in-depth testing. Usually, only 1 in 5 to 1 in 10 babies who fail the first hearing screen have a genuine hearing problem. However, it’s very helpful for that one baby to be picked up—early speech therapy can be crucial, and many of these babies could be candidates to have their hearing fixed via high-tech cochlear implants. Cool! So it’s a good idea to screen, but parents whose babies fail the first screen shouldn’t worry—they just need to follow up and have the more in-depth testing done. Chances are, their baby is fine. The newborn “metabolic screen” (often called a “PKU”) similarly is only a screening test. Most babies picked up as “hypothyroid” on that test turn out to be normal. But for the babies who are found to be truly hypothyroid, a simple medicine can prevent severe mental retardation. That’s an important screening test!

It’s hard not to worry when a test comes up “bad.” But keep in mind that many routine tests are just screens and often don’t mean that your child is in trouble. Screening tests are meant to screen for kids who might have a treatable problem, so it can be verified with a more definitive test. Try not to worry, at least until the follow-up testing is done—and then keep in mind that if the final test is normal, there’s nothing to worry about.