Screening tests

A few weeks ago I read in the Newsweek magazine an article about screening tests and others medical procedures that is quite interesting. The text can be found here. In summary, the text is about medical procedures aimed to save the patient that can in fact harm more than cure. This is not the first time I see this. For a very good CBC radio program about the dangers of the PSA screening test for prostate cancer, and screening tests in general, see here. And also here for screening tests in general.

People usually think that if a procedure can detect or fix something bad then it is a good procedure. The problem is that no procedure is perfect. Screening tests can fail and detect the disease on somebody that does not have it. Invasive medical procedures can cause not desired affects and cause damage to health parts of the body. In the case of screening tests it is often the case that a very small part of the population has the condition the test is looking for, therefore a large number of healthy subjects will be tested unnecessarily, often not without adverse effects. The adverse effects that the test has on healthy subjects may not worth the lives saved with early detection by the test.

One of the procedures not recommended in the Newsweek text is the electrocardiogram for people that don't feel anything in the heart. Another is the MRI for lower back pain. And then I have some personal experience with these.

In Brazil, if you are a runner, you will be advised a lot to do a hearth check up "Everybody should do a heart check up before practicing physical activities to make sure they can run". Is there any scientific foundation for this recommendation? I think the reason for this is legal more than based on scientific evidences. Race organizers and coaches may be sued if athletes die on their hands. By making heart check up mandatory, they make doctors accountable rather than themselves. And if the heart check up (which of course involves electrocardiogram) harms the runner more than save their lives, then the runners are also paying a price for the lack of evidences. We could think that runners are more at risk of having something on their heart (I strongly disagree!) and then maybe an electrocardiogram would be justified. But we still need something showing that. Also, I see very few runners dying while running (but they become news among runners very fast!) and when someone dies, I often don't see convincing argument that it was because that runner had some sort of untreated heart condition. I mean, where is the data that shows that fewer runners who go through a check up die compared to those who don't go through heart check up?

The second story is about the lower back MRI. I went to the doctor and I told him I occasionally had this back pain. Very occasionally since I haven't had a bad back pain for more than two years now. It was just a routine exam, I was not complaining about my back, but he asked if I have felt any pain so... He said I should go through an MRI to see what is happening with my lower back. I refused to do it because I did not have time then, but now I see that perhaps I did the right thing. It seems clear that many doctors don't have this sort of training on the importance of data based evidences. They think the MRI is the right thing to do because the MRI will allow them to see everything and this can only be a good thing...