This thoughtful and very accessible explanation by a Canadian Doctor about
what EBM is and how powerful an effect it has on patient care was in the
Sunday NY Times Magazine.
Enjoy,
Elaine Alligood,
Information Specialist
VA Technology Assessment Program
Boston, MA
-----------------------------------------
What Doctors Don't Know (Almost Everything)

May 5, 2002

By KEVIN PATTERSON

I work as an internist in the Canadian Arctic, in a region
called Kivalliq, on the west coast of Hudson Bay. There are
no highways there, and the more recent social changes of
the south have not penetrated the tundra any more deeply
than the road system has. The eyewear is distinctly out of
fashion, and the church remains influential.

In Kivalliq, interaction between patients and physicians is
not characterized by lengthy debate. People expect to
receive prescriptions and proscriptions; these are
provided, and patients generally keep their opinions to
themselves. It is the postcolonial era, but not by much.

I also work on Vancouver Island, and there, the eyewear is
outlandish and churches are being sued everywhere. The
interaction between patients and physicians, however, is
the least different thing about the two places. There is
somewhat more dialogue in the south, to be sure, but the
tone of the interaction is for the most part lodged in the
Edwardian era. You must stop smoking. If you don't lose
weight, you're destined for diabetes. You have congestive
heart failure. Here is a prescription for the drugs you
need to take; please don't forget. The finger wagging is
unceasing.

Medicine has clung to a sense of hierarchy that is being
abandoned elsewhere. Teachers answer to parents and bankers
solicit borrowers, but in medicine, a chain of command has
existed since the profession found its modern face --
doctor's orders -- with the most senior and academic
physician experts directing the decisions of specialists,
family physicians and ultimately the patients.

This order is now in the throes of a revolution known as
evidence-based medicine, which asserts the supremacy of
data over authority and tradition. For doctors these days,
the revolution is everywhere; you can't kick over a bedpan
without hearing the phrase ''evidence-based medicine''
rattle out. Outside the hospital walls, though, word has
been slower to travel.

E.B.M. is, as revolutions go, a little unlikely. Its
motives are not primarily political, although its effects
ultimately are. And those effects -- the various ways in
which information subverts hierarchy -- are beginning to
change medicine fundamentally. What began as a pragmatic
undertaking has become a philosophical and political
transformation, and it is creating a dramatic shift in the
relationship between doctors and patients.

Until recently, the guiding principle in medicine has been
Aristotelian: an understanding of the disease comes first,
before experimentation. On the face of it, the approach
isn't outrageous; doctors try to understand the nature of
the ailment they are addressing, and then they try to think
of an intervention -- an operation or a pill or a type of
psychotherapy -- that goes to the essence of the problem.
And this method often works. For instance, when Frederick
G. Banting and Charles H. Best identified the role a
deficiency of insulin played in the development of juvenile
diabetes, the treatment that suggested itself -- replacing
the insulin -- turned out to be a huge success. Banting and
Best's discovery was a model of how medicine advanced
through most of the 20th century. Research was based on
this simple, rational premise: understand the problem, and
its solution will become self-evident.

But people, doctors included, have a tendency to see what
they expect to see. It's the premise of every
sleight-of-hand game. If it makes sense that a treatment
will work -- or if one stands to make money if a treatment
works -- then a doctor will, with alarming and
disheartening reliability, perceive that it does in fact
work. What is surprising is that a profession that dresses
itself up in the garb of science has taken so long to
acknowledge a principle that every small-town carny
understands.


When I started practicing medicine in the early 90's, one
of my enthusiasms was hormone-replacement therapy. At that
time, the observation had been made, repeatedly, that
postmenopausal women who happened to take estrogen -- for
osteoporosis or hot flashes, for instance -- were less
likely to have heart attacks and strokes than women who
didn't. I remember telling women in their 50's how
premenopausal women were relatively immune to
cardiovascular disease, at least compared with men, but
that once they had been through menopause, this relative
protection disappeared quickly. ''Take the estrogen,'' I
suggested over and over. ''Preserve your youthful
coronaries.''

This was in Manitoba, and these were pragmatic, sensible
prairie women. I insisted to them that the recommendations
and the evidence seemed clear. I remember my patients'
brows knitting at the thought of menstrual cycles extending
into their dotage, but ultimately the argument felt
compelling. Certainly it did for me. I remembered being
told in medical school that the underuse of estrogen was
one of the great crimes of the medical patriarchy, itself
an expression of latent misogyny. No misogynist I, off I
went to work, my prescription pad leaping to hand at the
sight of bifocals or pastel cardigans.

Then in 1998, the results of a formal, placebo-controlled
clinical trial called the Heart and Estrogen/Progestin
Replacement Study (HERS) were published. It showed that
estrogen did not prevent heart attacks or strokes and, in
fact, it made women more susceptible to blood clots. The
net cardiovascular effect therefore was negative. This
study astonished most doctors -- for me, it certainly felt
like a betrayal. Betrayed by the recommendations, we had in
turn betrayed many of the cardigan-clad women of our
acquaintance.

A few months ago, in the emergency room of one of the
hospitals I work in on Vancouver Island, I saw a woman in
her mid-70's who was still taking Premarin, a common
estrogen preparation. She had been having chest pain, and I
was admitting her for observation, to make sure she wasn't
having a heart attack.

''So, you take the Premarin because . . . ?'' I asked.


''My sisters all had heart attacks in their 50's,''she
said. ''My doctor said the estrogen lowered my risk.''

''We now think it probably doesn't.''

''Really.''


''Yes.'' Me, nodding, smiling weakly.

''What changed?''

''Well, there were these studies that
seemed to show that women who took estrogen had a
relatively low incidence of heart attacks, but it turns out
that really, it was the sort of woman who took estrogen who
was less likely to have a heart attack. She was probably
also less likely to smoke, more likely to seek regular
medical attention -- she did something important different,
anyway. When, just recently, they took a large group of
women and randomly gave each woman either a placebo or
estrogen, the ones taking estrogen didn't do at all
better.''

''Well,'' she said. ''Isn't that something?''

My patient was not alone. The data from HERS were so
surprising that many health-care providers seem not to
believe them, even today. In 2001, Premarin was the third
most-prescribed drug in the United States.


Until only a few generations ago, the prevailing conception
of illness was that the sick were contaminated by some
toxin or contagion or an excess of one humor or another.
That understanding of illness contained within it the idea
that these conditions could be improved by opening a vein
and letting the sickness run out: bloodletting, the
practice was called.

Once the toxins were gone, the patient immediately felt
different, and often better. As anyone who has given blood
can tell you, losing a pint or two can make you feel
transported, transformed. Intuitively, it was satisfying to
doctors that the procedure left the patient feeling drained
-physically, emotionally and into the sink.

It is understood now that bloodletting only hastened the
death of the ill. (George Washington had almost five pints
of blood drained from him in the two days prior to his
death; he had been suffering from a sore throat.) We know
that bloodletting is unhelpful because a Parisian doctor
named Pierre Louis did an experiment in 1836 that is now
recognized as one of the first clinical trials. He treated
people with pneumonia either with early, aggressive
bloodletting or less aggressive measures; at the end of the
experiment, Dr. Louis counted the bodies. They were stacked
higher over by the bloodletting sink.

No sooner had the message about the dangers of draining
blood out of patients been conveyed across the medical
community -- and that took the rest of the 19th century --
than doctors developed a new passion for pouring it back
into them. After crosstyping was invented and blood could
be transfused safely, doctors quickly decided that very ill
patients do better with as normal a level of hemoglobin as
could be maintained. It made sense, and blood transfusions
became a routine part of critical-care medicine.

Then just three years ago the results of a large study
called Transfusion Requirements in Critical Care were
published in The New England Journal of Medicine. Those
results shook the community of intensive-care physicians
worldwide. Except in the case of people with unstable
angina and acute myocardial infarction, routine transfusion
of critically ill people with moderate or mildly low
hemoglobin levels does not decrease their mortality rate --
and in some subgroups, it actually increases the mortality
rate. Nobody has a convincing explanation for why this is,
but it is the case.

The essential tenet of evidence-based medicine is that
patients, working with their physicians and armed with
medical data, are better equipped to make decisions that
work for them than doctors of the Marcus Welby model are,
because they understand their own expectations better than
their physicians can. Authority is devolved from expertise
to the data and thus, ultimately, to the patient. In an
E.B.M. world, the physician makes diagnoses, serves as a
conduit of the medical data and is responsible for framing
those data and putting them into context, but the
responsibility for the decision becomes the patient's.
Patients have always had the final say about whether to
accept the recommendations of their physicians, but without
the actual data in front of them, the decision has simply
been whether or not to trust the wisdom of the physician.
E.B.M. tries to move that judgment to the steadier ground
of data.

The point isn't that some medical treatments don't work as
well as it is thought, or even that in treating patients,
doctors sometimes hurt them -- this has always been true.
The point is that the conclusions doctors reach from
clinical experience and day-to-day observation of patients
are often not reliable. The vast majority of medical
therapies, it is now clear, have never been evaluated by
systematic study and are used simply because doctors have
always believed that they work.

The manifesto of the evidence-based-medicine movement
appeared in The Journal of the American Medical Association
in 1992, written by a group of doctors led by an
internal-medicine specialist in Hamilton, Ontario, named
Gordon H. Guyatt. The publication ignited a debate about
power, ethics and responsibility in medicine that is now
threatening to radically change the experience of health
care.

''If you said to most members of the general public,
'Physicians have been trained in such a manner that they
have no idea how to read a paper from the original medical
literature or how to interpret it,' that would surprise the
public,'' Guyatt says. ''The public's image of physicians
has been such that it would be shocking to them that there
hasn't always been evidence-based practice.''

From the first day in the cadaver room and on, every
medical student is drilled with this truism: ''Medicine is
both an art and a science.'' The ''art'' is represented to
be the physician's intuitive sense of a patient and her
underlying diagnoses and how she might respond to certain
treatments.

And intuition is certainly an indispensable part of
medicine. The body is so complex, and the ways it might go
wrong so varied, that in the middle of the night, standing
next to some fresh catastrophe, a doctor sometimes needs to
generalize and to reduce very complicated problems to first
principles. It is simply not possible to be rigorously
intellectual and consult the available medical data about
every single thing, all the time. It takes too long, and if
all the intricacies of the medical data on every clinical
problem were fully considered before acting, the operating
rooms would grow dusty and people would die while the
doctors' chins were rubbed into a bright shine. Sometimes
it is necessary to act on a feeling.

And so medicine has intellectual shortcuts: intuitions and
axioms and rules of thumb: ''Never let the sun set on an
abscess'' (operate early when you find one) or on a more
particular note, ''Gerald hasn't looked right for months
now; this isn't just a cold.''

The feeling, the art, is precisely what is appealing about
medicine for doctors. It is personal and warm, and
dramatic, pithy platitudes about the indications for
surgery are easier to remember and more satisfying to cite
than the constantly changing and dry data on outcomes. But
in the end, the art is simply what one wants it to be. And
if a doctor simply feels that blood transfusions are good
for people with pneumonia, should that be enough reason to
transfuse them?

The answer has always been, pretty much, yes. Clinical
impressions do matter and ought to be taken seriously. When
an experienced neonatology nurse doesn't like the look of
an infant, for instance, a pediatrician takes that very
seriously, or quickly learns to, even if there is no fever
or abnormal lab results. It sounds a little like magic,
this art. And once you believe a little in magic, it's hard
to imagine there's anything it can't do.

Nuala Kenny, a physician-ethicist at Dalhousie University
in Halifax, Nova Scotia, and a critic of evidence-based
medicine, defends intuitive reasoning: it isn't a lazy way
of thinking, she argues, but rather a sophisticated type of
thought that incorporates many variables and tremendous
amounts of data from previous experience. It's the reason
that Kasparov can still beat Deep Blue from time to time.

''Scientific data cannot be expected to guide most medical
decisions directly,'' she wrote in one critique. ''There
are not enough randomized trials or epidemiologic studies;
there are virtually no studies on appropriate ordering of
tests. The randomized clinical trial has become the gold
standard but . . . it is a leap of faith to expand the
results of a trial to a broad therapeutic principle.
Clinicians recognize this instinctively. The best drug, the
optimal dose and duration of therapy for a particular
patient are not determined directly by a study involving a
large population.''

Kenny sees E.B.M. as a threat to the individual
practitioner, another step toward the mechanization of
medicine. Guyatt emphasizes that E.B.M. gives the
individual practitioner the tools to defend iconoclastic
practice with data. E.B.M. represents a more skeptical
approach to practicing medicine, but at the same time a
more open one, Guyatt argues. If the data support an
intervention, even if it is herbal or crystal-based or
otherwise magical-seeming, then the intervention should be
put into practice. St. John's Wort, for instance, has been
demonstrated to be an antidepressant of modest potency in
randomized clinical trials and thus, in the E.B.M.
worldview, there is nothing ''alternative'' about it.

The disagreement is really over the value of intuition: the
E.B.M. position is that there are reliable, validated data,
and then there are data that aren't reliable and validated,
and that's really what matters. This difference may never
be resolved through debate; it might be the difference
between having faith and not having it.


The most radical change E.B.M. proposes will occur in
everyday visits in doctor's offices -- those simple, scary
moments when the most important medical decisions are made.
The instant the practitioner stops saying, ''I think you
should take this therapy,'' and starts saying, ''The
evidence is that this therapy will work this percent of the
time, with these complications, this frequently; what do
you want to do?'' then the power hierarchy of doctor over
patient is collapsed, and autonomy is assigned to the
patient. This is how the relationship between doctor and
patient could be changed by evidence-based medicine. Just
as the idea of authority within medicine is rejected, so
too, the idea of the profession of medicine itself having
authority over the patient is rejected. Giving authority to
the data, instead of other people, empowers everyone, the
movement holds.

It isn't clear that patients will embrace evidence-based
medicine. Human beings are social creatures, and we don't
necessarily want to have to make up our own minds about
absolutely everything, especially if doing so requires
trips to the library and afternoons on the Internet and
hours of reflection.

Practitioners are also resistant to E.B.M., simply because
it marks a change in the idea of what doctors are. It is a
signal that in medicine, ours is a less heroic age. The
dramatic cures have stopped coming. Penicillin for
meningitis, streptomycin for tuberculosis, Salk and polio:
what those days of discovery must have been like, with
self-evident cures trotting forth regularly for all the old
killers. Everyone used to die of this, now almost everyone
recovers -- the only trick is in making the diagnosis. How
satisfying it must have been, how easy to feel potent.

Now we die of things like congestive heart failure:
diseases that haven't submitted to easy, magic-bullet cures
and have the habit of announcing their presence quietly
when they are already well advanced. These diseases are
pared away incrementally, the mortality rate decreased by a
few percentage points with this maneuver, a few more with
that one. A number of things help a bit; nothing helps a
lot.

So the warriors are being replaced by the accountants. The
28 percent response rate is traded for the 31 percent
response rate; differences in effectiveness that are too
subtle to be noticed by an individual practitioner justify
ongoing refinements in therapy. The numbers dictate the
changes, and each year the outlook is slightly better.

Accountants know the whole world thinks their lives are
gray -- demeaned by all that addition. Doctors aren't used
to thinking of themselves that way. But in the real world,
where numbers matter, accountants know how powerful they
are. Doctors now have to learn the same lesson.

No one knows where the ongoing renegotiation of the
complicated relationship between the individual and
society, which lies at the heart of E.B.M., is going to
end. At the same time that the individual increasingly
demands control of his life, money and expression, he also
clearly still wants to be protected by society from
corporate interests and economic vagaries, and to be taken
care of when he is sick. This ambivalence about
independence is an essentially human trait, as is a certain
ambivalence about empiricism itself. The story is as old,
and Greek, as the Hippocratic tradition itself: what
empowers us sometimes demeans us.

Kevin Patterson is an internist and the author of ''The
Water in Between: A Journey at Sea.''

http://www.nytimes.com/2002/05/05/magazine/05EVIDENCE.html?ex=1021705276&ei=
1&en=83176fd5cf32b67c

Copyright 2002 The New York Times Company