When Preventative Medicine Doesn’t Prevent

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“An ounce of prevention is worth a pound of cure.” I remember hearing that many times as a child. I also remember the old oil filter commercials “pay me now or pay me later”. Prevention by definition seems to be a good thing to do.

CMS and the social media have caught on. Preventive services are available everywhere. Protocols have been developed and revised over the last thirty years in medicine. Obviously, primary prevention is important for heart disease, hypertension, diabetes, etc.,. There is no doubt that risk factor reduction (primary prevention) is good, and early recognition (secondary prevention) makes sense in many cases.

But on the other hand, look at tests such as PSA, chest X-rays, and even mammograms. There is increasing evidence that maybe routine screening is not helpful in these situations. PSA is now NOT recommended for routine screening and the role of screening mammograms is getting muddier and muddier. What seems to be the rub?

I believe that we simply forget a fundamentally important premise in the world of prevention and wellness:

Prevention is only good if early detection makes a difference in either survival or quality of life.

If that is not the case, why use the resources to “detect” it earlier? In fact, does it make any sense to diagnose an incurable disease sooner? On the other hand, if there are medical treatments available that would effect the course of the disease, early recognition makes a ton of sense. We need to be able to truly determine whether early recognition can alter the ultimate course of the disease.

The fact is for many of our most common screening conditions, the issue is simply not straight forward. It is complicated by the fact that early detection of an otherwise incurable disease will falsely appear to increase the survival time with the disease. Known as lead-time bias, earlier detection of an otherwise incurable disease does not alter the disease course one bit, but only lengthens the time that the patient knows about it. The patient still succumbs to the disease at the same point on the time line. The actual course of the disease did not change. Lead time bias may play a big role in lung cancer screening, for example. A lesion may be detected asymptomatically on the chest X-ray or even the CT, but has the damage already been done from the perspective of survival.

The best end point to evaluate the role of prevention and early detection is the age-adjusted mortality. If we do not improve that number, the prevention process did no good. We have improved the age-adjusted mortality for some cancers, but not for others. We need to continue to revise our protocols for prevention keeping that end point in mind.

Prevention is good, but only if the early detection makes a difference for the patient. Otherwise, prevention does not really prevent.

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