TOO MUCH SENSITIVITY

Those of you that have been following my rants aren’t likely to accuse me of the above; but in this case I’m not talking about a state of emotion. I’m referring to laboratory testing.

The ideal diagnostic test is 100% sensitive for detecting what you’re looking for, and 100% specific, meaning you’re not getting any false-positives. These two things determine the positive and negative predictive value of any test, and take on added importance when used as screening tests that, by definition, involve large groups of people. Despite some improvements with time, perfect tests don’t exist in any field, although one might not guess this from the hype.

I’ve discussed in the past how a simple screening blood test called a D-dimer leads to oodles of normal chest CTs to exclude pulmonary embolism, or clots to the lungs. It’s a pretty sensitive test with poor specificity. So you’re less likely to miss this frequently elusive disorder, but you’ll be irradiating a lot of people at great expense to find a few.

With the recent, tragic demise of another high school basketball player hitting the news, a call for review of our policy regarding screening electrocardiograms for young athletes has again surfaced. Our current health screening process doesn’t include this, although that’s not always the case internationally. There is legitimate controversy regarding the utility of adding the inconvenience and expense of this additional test on a large scale. Proponents, of course, make the easy “what price can one put on the value of a young life?” argument. The problem is that the event rate is already extremely low and, while ECGs are likely to pick up a few more at risk individuals (i.e., some improvement in sensitivity), the specificity is poor. It will result in additional, more expensive testing and sidelining a number of individuals (how many, I can’t guess) that will never have a problem. How much do we spend and how many people’s lives do we change to prevent a few tragic early deaths. Millions? Billions?

The point is, until we have more perfect tests and screens, or unlimited resources, we have to be careful. We need to decide just how risk-averse we are. How much of our freedom and treasure are we willing to sacrifice for a bit more safety? In how many wilderness parks can we really afford to put up fences?

These are questions each individual must answer for his or herself, and the ruling class will inevitably decide on our behalf.

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