Medical testing and the risks of idle curiosity

Doctors use a lot of tests — blood tests, urine tests, x-rays, MRI scans, and quite a few others. Some of these tests carry well-known risks in doing them. For example, a few people have serious allergic reactions to the contrast dye used in certain x-ray tests. For most of the other tests, though, the immediate risk is so low to essentially non-existent. A needle stick hurts for a few minutes, but that soon passes. Getting a simple urine sample doesn’t hurt at all. So what is the harm in getting these kinds of tests because we’re curious what they will show? For example, the “as long as you’re drawing the blood anyway” question comes up frequently; after all, once the needle is in the vein, it’s easy to take a little extra blood for extra tests.

It seems innocent, but what most parents don’t understand is another, more insidious risk, one that using a shotgun approach to testing will bring — the risk the test will give misleading information. A blood or urine test, something of little immediate risk to the child, becomes potentially quite risky if the result will confuse the situation. What can happen is that the test, if just a little (and insignificantly) “abnormal” can lead to further tests and procedures, things that you never would have ordered in the first place. These further tests, in turn, carry further risks. To complicate matters even more, every medical test has a built-in, inherent error rate; the test result may just be flat-out wrong — it’s a statistical possibility. The rule of thumb I’ve often heard is that if you do 20 blood tests, statistically one of them will be falsely abnormal, a fake.

The scenario of an abnormal result in a test done for dubious reasons, leading in turn to more tests, and ultimately to some bad medical decision making, is a well known phenomenon.

My point is that it is never a good idea to ask your doctor to do tests on your child just because you (or your doctor) are simply curious about the result. Any test needs to be clearly justified by a child’s specific situation.