Tuesday, April 15, 2014

Over-diagnosed: making people sick in the pursuit of health, by Gilbert Welch

Everyone should read this book, but I fear that few will.  Partly because it is perceived as a difficult topic.  No worries there:  Dr. Welch and his co-authors make this as easy and straightforward a read as possible.  Even if you barely passed high school biology or math, you'll have no problems here:  the science is simple, the statistics are very clearly explained.

Another reason folks might not read this is that they are comfortable delegating their personal health decisions to physicians.  The facts indicate that this is not a good plan.  The whole point of Dr. Welch's research is that physicians often do things that provide no statistically significant improvement to lifespan but do have a statistically significant likelihood of negative side effects.

If your auto mechanic suggests an expensive diagnostic for your engine when you bring your well-running car in for a routine oil change, and then suggests a follow on test because the first was inconclusive, and these are expensive tests, and there's a chance that your engine will be ruined by the testing, you might want to have a better sense of what's going on.  If all this happens while your car is running perfectly well, with no symptoms of trouble, then you're in a situation quite analogous to the superfluous diagnostic medical scanning that Dr. Welch writes about.

Dr. Welch is careful to not pick on his colleagues.  Although he does note that a physician's primary sources of information tend to be funded by drug companies or medical equipment manufactures. In addition, there are many economic reasons to ignore science and statistics, sub-conscious or not.  A big factor is that a doctor, like anyone else, is often most comfortable with the "old wives tales" that they know.  This sort of thing has gone on for centuries.  One example, not from the book, is that of Dr. Ignaz Semmelweis.

Semmelweis noticed that mothers would give birth in a hospital's obstetrical clinic only to die of puerperal fever soon after -- with a mortality rate of 10% to 35%.   That's a scary amount of preventable death for a hospital.   He determined that if doctors would wash their hands with a chlorinated lime solution (similar to today's anti-bacterial soaps), they could take the mortality rate down to below 1%. You don't need to be a doctor nor a statistician to see that this is a good deal.  So what happened?

In spite of published facts, Semmelweis' observations conflicted with the established, normative medical practice of the time.  So his ideas were soundly rejected.   It took about 20 years before Dr. Joseph Lister succeeded in getting doctors to accept the science, and only then because he built on the concepts that Louis Pasteur introduced.   Most folks have heard of Listerine mouthwash, named after Lister. Nothing is named after Semmelweiss.   But lots of women died in those intervening years.

I use this example because it is so very obvious to us today that one should wash one's hands -- and yet, it took decades to get doctors to do it.  It is difficult to realize sometimes that throughout history scientists have been labeled heretics because their data did not conform to then-current practice.  In the 21st century we tend to feel as though every problem has been solved, and that we've got it all right. But maybe not so much, and Dr. Welch's book points out clear examples of facts not convincing physicians.  This problem of normal practice not aligning with the facts, but going on anyways, is old news.  It happened to Galileo, who had the audacity to propose that the earth rotates around the sun.  It happened to Semmelweiss, and many others.  And as Dr. Welch's book makes quite clear, it happens yet today.  

Okay, so back to the book for some modern day examples.  Back in 1996, the US Preventative Services Task Force (USPSTF) recommended against routine obstetrical ultrasound.  Why?  Because they found that there is just no substantive benefit.  The highly respected Cochrane Collaboration (which eschews any financial support from drug firms or equipment companies) agrees.  But every single expectant mother that I have met since 1996 gets an ultrasound; I bet that's true for you too.   The USPSTF has given up on the topic, because they recognize that this unhelpful and potentially negative scanning procedure is such a common practice that no one would listen to them anyway.   [pp112-113] Yikes.

But there's more.  Also in 1996, the USPSTF recommended against routine fetal monitoring (the belt put around an expectant mother to monitor the about-to-be-born baby's heart beat).   Once again, the Cochrane Collaboration agreed, noting that monitoring increased C-section rates by 66%, and that the risk of that to baby and mother is enormously worse than the potential benefit.  What is that benefit?

About one in a thousand babies would avoid a (non-fatal) seizure compared to two in a thousand without the monitoring.  A one in a thousand change.  But even then, no improvement in baby's health as measured by Apgar score, respiration, pulse, conditions like cerebral palsy, need for ICU - nothing.   Yet, again, it is such a common practice that the agency feels it would be tilting at windmills to try to change it (even though doing so would clearly, from the numbers, save lives and reduce negative side effects).  [pp105-106]  Did I say, Yikes?

There's lots more in the book, from mammograms to PSA tests to blood pressure and diabetes.

By now you should be considering that there is real value in reading this book, if only to make us better informed consumers of the medical industry.

Dr. Welch has done an extraordinary job of stating the facts, acknowledging the ambiguities, and making it clearer for individuals to understand the tradeoffs of their diagnostic scanning choices.   Even if you continue to use screening that the facts might indicate you oughtn't, you'll have a better understanding of what the issues are.


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