Clinical Epidemiology: A Basic Science for Clinical MedicineBMJ 2007; 335 doi: https://doi.org/10.1136/bmj.39349.461678.43 (Published 11 October 2007) Cite this as: BMJ 2007;335:777
All rapid responses
It’s heartwarming to have the BMJ and Dr. Shaughnessy publish nice
things about our work while we all are still alive to thank them for it.
As frequently occurs in such reviews (and in this case no doubt
exacerbated by the word restrictions imposed by a single column) we’ve
been given too much credit for some ideas and accomplishments, and too
little background for some others.
For example, credit for publishing the first modern text in clinical
epidemiology in 1982 goes to the Chapel Hill trio of Bob and Suzanne
Fletcher and Ed Wagner , who had invited one of us to join them just as
we were starting ours. We delayed the publication of our 1st (1985)
edition for a year as we sent its first draft ‘round to several colleagues
for their critiques, and tried out bits of it in the CMAJ (as Clinical
Epidemiology Rounds), all in an effort to improve clarity and avoid dumb
Similarly, credit for the NNT we introduced in our 2nd (1991) edition
 must be shared with Andreas Laupacis, who brainstormed it with Dave
Sackett in a coronary care unit one morning to try to help the house staff
understand the reduced benefit (high NNT) of starting a powerful (high
relative risk reducing) beta blocker in a low risk patient . And much
of the NNT’s current value resides in the ways that colleagues like Sharon
Straus have transformed it into more personal measures such as the
likelihood of individual patients being helped vs. harmed by specific
One of us did, in fact, define clinical epidemiology when starting
that department at the new McMaster medical school back in 1967  (“the
application, by a physician who provides direct patient care, of
epidemiologic and biometric methods to the study of diagnostic and
therapeutic process in order to effect an improvement in health.").
However, by the time we published our 1st (1985) edition, not only had we
become confirmed nominalists, but also we had recognized that all sorts of
non-clinicians (including economists and other social scientists) had
begun to make major contributions to the field. Accordingly, we traded a
tortured essentialist definition for silence, a decision reinforced by the
subsequent contributions of ever more disciplines to the enterprise.
By the early 1990’s, not only were the first two steps of finding and
critically appraising evidence to a useful level well underway, but we
also had begun to get a handle on the crucial third step of applying their
results in practical ways to the care of patients. One of us saw the need
to recognize (and celebrate) the ability of this combination of skills and
attitudes to revolutionize health care, assembled a group of us to
describe how it might be accomplished, and suggested we label it with a
new name: “evidence-based medicine.”  Our idea caught on, and by 2006
over 200 EBM papers were being published every week.
One of the “side-effects” of the resulting explosion was our decision
to supersede our earlier clinical epidemiology texts with more evolved
books on EBM [8,9]. Another was our realization that good research
methods for generating the valid, useful evidence about diagnosis,
prognosis, therapy demanded by EBM had become ever more important.
Accordingly, our 3rd (2005) edition of Clinical Epidemiology  is
devoted to methods for conducting the clinical practice research that
supplies the scientific base for EBM.
Finally, a minor quibble: Dave Sackett defined “experts” in terms of
their subject matter, not their scientific methods. In fact, he did heed
his own call for the compulsory retirement of experts and never again
wrote, spoke, or refereed about matters of patient compliance from 1983 on
, or about EBM from 2000 on .
1. Fletcher RH, Fletcher SW, Wagner EH. Clinical Epidemiology – the
Essentials. Baltimore: Williams & Wilkins, 1982.
2. Sackett DL, Haynes RB, Tugwell P. Clinical Epidemiology: A Basic
Science for Clinical Medicine. First Edition. Boston: Little, Brown,
3. Sackett DL, Haynes RB, Guyatt GH, Tugwell P. Clinical
Epidemiology: A Basic Science for Clinical Medicine. Second Edition.
Boston: Little, Brown, 1991.
4. Laupacis A, Sackett DL, Roberts RS. An assessment of clinically
useful measures of the consequences of treatment. N Engl J Med
5. Straus SE. Individualizing treatment decisions. The likelihood of
being helped or harmed. Eval Health Prof 2002;25:210-24.
6. Sackett DL. Clinical Epidemiology. Am J Epidemiol 1969;89:125-8.
7. Guyatt GH. Evidence-Based Medicine [editorial]. ACP Journal Club
1991:A-16. (Annals of Internal Medicine; vol. 114, suppl. 2).
8. Sackett DL, Richardson WS, Rosenberg W, Haynes RB. Evidence-Based
Medicine. How to Practice & Teach EBM. Edinburgh: Churchill
9. Users' Guides to the Medical Literature: A Manual for Evidence-
Based Clinical Practice. Guyatt G, Rennie D, eds. Chicago: American
Medical Association, 2002.
10. Haynes RB, Sackett DL, Guyatt GH, Tugwell P. Clinical
Epidemiology (Third Edition): How to Do Clinical Practice Research.
Philadelphia: Lippincott, Williams Wilkins 2005.
11. Sackett DL. Second Thoughts. Proposals for the Health Sciences –
1. Compulsory retirement for experts. J Chron Dis 1983;36:545-7
12. Sackett DL. The sins of expertness and a proposal for redemption.
We wrote the books.
Competing interests: No competing interests
I have been an avid reader of the Evidence-Based Medicine literature,
having learned from the works of David Sackett, Gordon Guyatt, and have
used the database searching tools developed by Brian Haynes on PubMed, of
the Medline database.
My biggest revelation was my realization that these concepts were not
fundamental to a medical education. After all, physicians are the students
who received straight A grades in mathematics, biochemistry, physics, and,
I thought, had a natural affinity for such probabilistic sciences. The
defination of "Number-Needed-To-Treat" (1/Absolute Risk Reduction)did not
seem like advanced mathematics. I assumed, naively, that a pre-med student
would have come up with the forumula independently.
Allen Shaughnessy's review of "Clinical Epidemiology: A Basic
Science for Clinical Medicine" hits the nail on the head when he describes
the medical outsider's response to an explanation of the principles of
An explanation of how decisions should be based on the best evidence
rather than solely on personal experience will be met with a reaction I
often hear: "You mean you have to TEACH doctors to do this?"
Competing interests: No competing interests