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AARP
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September & October 2008
Page 34
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Health Report
Why Doctors Make Mistakes
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by Jerome Groopman, MD
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Too often physicians make snap decisions. Here are three questions to help get
you to the right diagnosis.
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Not long ago I spoke with a middle-aged woman whose mother had
been misdiagnosed with Alzheimer's disease. The elderly
woman's memory was fading, and her family was close to
admitting her to a nursing home.
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Luckily, the family decided to get a second opinion from a neurologist at a
different hospital. It turned out the woman did not have Alzheimer's at all
but, rather, vitamin B12 deficiency, a well-recognized cause of dementia. Her
mild anemia, also due to vitamin B12 deficiency, had been written off by her
internist as being due to "old age." Injections with the vitamin fully
reversed the anemia and restored her thinking.
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Unfortunately, misdiagnosis is not a rare phenomenon. About
15 percent of all patients are misdiagnosed, and half of
those face serious harm, even death, because of the error.
And, contrary to the general impression that misdiagnoses
result from technical foul-ups such as mislabeled x-rays, in
fact most cases are due to mistakes in the mind of the
doctor.
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Making an accurate diagnosis involved arranging the findings
from physical examination and laboratory tests into a
pattern. A doctor superimposes this pattern onto a template
of the typical case that exists in his or her mind. But
this effort at pattern recognition doesn't always work. Why
not?
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First, there may be incomplete or misleading information.
Patients may not feel comfortable reporting all their
symptoms to a doctor - or, as studies show, physicians may
prematurely cut off a patient who is reciting his or her
problems. Second, pattern recognition is difficult because
cases may not be "typical." Diseases can have different
manifestations, sometimes quite subtle, because every
individual is different. Most significant is how the doctor
selects the clinical elements, weighs their importance, and
arranges them in his or her mind, a process that can result
in several different patterns, leading to quite different
diagnoses.
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There are three major cognitive mistakes that can occur in
the mind of the doctor and lead to misdiagnosis.
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The first is termed "anchoring," meaning the tendency to grab on to the first
symptom, physical finding, or laboratory abnormality. Such snap judgments may
be correct, but they can also lead physicians astray.
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A second common cognitive error is termed "availability." This refers to the
tendency to assume that an easily remembered prior experience can explain the
new situation the doctor is trying to diagnose.
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The third mistake is thinking is termed "attribution," and this accounts for
many of the misdiagnoses in the elderly. Attribution refers to the tendency to
mentally invoke a stereotype and "attribute" symptoms to it. Alas. Often this
stereotype is a negative one, such as an older person who is seen as a
complainer, a hypochondriac, or a person unable to cope with his or her
naturally declining abilities. The doctor ignores the possibility of an
illness not specifically linked to "old age."
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What can a patient do to help prevent medical thinking from going astray? I
have formulated three simple questions to ask. It is quite appropriate to pose
these questions to a doctor when he or she is making a diagnosis.
- What else could it be? This question helps to prevent
an anchoring error or an availability error, where a
diagnosis is formulated too quickly in the physician's mind
because it corresponds to the initial symptom or because it
is most familiar to the doctor.
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- Could two things be going on to explain my symptoms. In
medical school doctors are taught to be parsimonious in
their thinking meaning they are taught to identify a single
cause to explain a variety of symptoms. But sometimes a
patient can have two medical problems simultaneously.
Physicians sometimes stop searching once they find an
initial problem, even if the patient does not fully
recover.
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- Is there anything in my history, physical examination,
laboratory findings, or other tests that seems not to fit
with your working diagnosis? All physicians tend to
discount information that seems to contradict their
hypothesis. This bias can lead a doctor down the wrong
path; his or her anchor diagnosis may be so firmly fixed
that this leads to ignoring contradictory data.
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In some instances, these questions may cause the doctor
to go back and reexamine assumptions, to think again, and
to come up with a different, and now correct, diagnosis.
All doctors want the best treatment for their patients,
and the best treatment involves the most open-minded
thinking.
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Jerome Groopman, M.D.
is the author of The New York Times
best seller
How Doctors Think
(Mariner Books, 2008)