I find medicine is the best of all trades because whether you do any
good or not you still get your money.
Moliere:A Physician in Spite of Himself," 1664
Small incidents during one's medical training can have a lasting
impact. A professor of mine invented one of the first "small parts"
ultrasound scanners, which allowed one to view very small organs, like
the thyroid gland, for the first time. He put the scanner on himself
and noticed two thyroid nodules, which could have been thyroid cancer.
It turns out(unknown at the time) that small nodules are pretty
common, and usually not cancer, but my professor lived through several
years of worry. The lesson I learned was never to do a medical study
unless there was a good reason to do it, as you might find something
you really don't want to know about(called an incidental finding).
During my entire career as a Radiologist, I cautioned people against
doing CT's and MRI's for questionable indications "just to be sure",
because of these incidental findings.
A new study, referenced above, gives proof of these lessons. The
investigators demonstrate that medical imaging studies, when done on
otherwise healthy patients, show abnormal findings 40% of the time.
Most notably, these abnormal findings are almost never of any medical
significance. Rather than finding diseases early, such studies reveal
harmless, incidental lesions which generally do not cause problems.
The papers discuss in detail the ethical issues involved which are
important. Unfortunately, ethical issues are secondary in our
litigious society. In real medical practice, these findings require
expensive follow up and sometimes invasive biopsies, as ignoring them
exposes any physician to unacceptable malpractice risk.
The societal implications are clear, large scale screenings studies,
done without medical indications, are not cost effective, and may be
dangerous. As discussed in a prior post on Bayes theorem(August 30),
these findings underscores the importance of making sure the incidence
of disease in a given population is large enough to avoid an
overwhelming number of false-positive examinations.
A crucial distinction needs to be made however. Simple tests designed
to measure one thing, like blood pressure or cholesterol do not lead
to incidental findings. It is only when studies like CT and MRI, which
demonstrate extensive anatomic detail of multiple organ systems that
such problems occur.
This study reinforces the points I have been making regarding common
sense and medicine. As natural as it would seem that "finding things
early" makes sense, the reality is far different. Lacking firm
indications doing such studies on healthy people is expensive and
counterproductive. From a national policy perspective, it is crucial
that well intentioned, seemingly sensible policy decisions are
actually backed by science. The recent issues raised by the FDA
regarding Pomegranate juice and genetic engineered salmon underscore
this issue, more to follow.
"Although [incidental findings] may offer the possibility of
substantial personal benefit to the participant, more commonly they
are false-positive findings that lead to a cascade of further testing
that presents additional risks and burdens,"
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