**Introductory question for participants: How would you define
evidence-based medicine?*Two fundamental questions need to be
addressed in medical practice: First, what is the purpose of
medicine? Second, how do I decide what to do? Just as a person
planning a cross-country trip maps out the journey based on
decisions about the most desirable destination and the most
desirable routing, so in medicine physicians must work with
patients to decide on both overarching goals, and on the best way
to reach those goals. In both travel and medicine, you have to know
where youre going before deciding how to get there. *While medicine
has many facets, including direct patient care, public health, and
research endeavors, the common goal of all medical ventures is
improving the quality of patients lives. This common underlying
goal can serve as the destination to guide all medical journeys and
endeavors, regardless of which facet or field of medicine is the
stage for the patients medical journey. *In a much-quoted 1996
editorial, David Sackett, an early and prolific author on
evidence-based medicine, defined evidence-based medicine (EBM) as
the conscientious, explicit, and judicious use of current best
evidence in making decisions about the care of individual patients.
(A) (italics added) This characterization highlights the three
important parts of evidence-based medical practice: the patient,
the evidence, and careful application of generalized evidence to
the individual patient.
(A) Sackett DL, Rosenberg WM, Gray JA, Haynes RB, Richardson WS.
Evidence based medicine: what it is and what it isn't. BMJ. 1996
Jan 13;312(7023):71-2. PMID: 8555924
(http://www.bmj.com/cgi/content/full/312/7023/71)*Sackett goes on
to argue that EBM is not old hat or just the same old medical
practice, as evidenced by the wide variation that often occurs in
clinical practice patterns. Neither is it intended to be cookbook
medicine as EBM specifically advocates for individualized
application of evidence to patient care, not forcing patient care
to conform to generalized evidence. Further, EBM is not intended
primarily as a savings tool it is intended to guide practitioners
to provide the best, not necessarily the cheapest, care. Lastly,
EBM is not intended to be only concerned with randomized controlled
trials, but with the best relevant evidence applicable to the
situation in question.
(A) Sackett DL, Rosenberg WM, Gray JA, Haynes RB, Richardson WS.
Evidence based medicine: what it is and what it isn't. BMJ. 1996
Jan 13;312(7023):71-2. PMID: 8555924
(http://www.bmj.com/cgi/content/full/312/7023/71)*Evidence-based
medicine was first introduced in the mainstream medical literature
in a 1992 article, Evidence-based medicine: A new approach to
teaching the practice of medicine, which presented EBM as a
fundamentally new approach emphasizing question formulation, search
and retrieval of the best available evidence, and critical
appraisal of the study methods to ascertain the validity of
results. (B) A subsequent series of Users' Guides to the Medical
Literature presented skills for searching for, appraising, and
applying various types of published evidence to medical practice.
As EBM gained prominence in the late 1990s and beyond, three
streams of evidence dissemination developed: 1) systematic reviews
gained increasing prominence in the medical literature, 2)
knowledge search engines (including internet engines such as
Google, and medline interfaces such as Ovid) became standard tools
for medical literature searching, and 3) knowledge distillation and
push services developed as a way to compile and disseminate concise
reviews of evidence on specific topics or questions (eg, ACP
Journal Club, InfoPoems, etc). (B)
(A) Evidence-Based Medicine Working Group. Evidence-based
medicine. A new approach to teaching the practice of medicine.
JAMA. 1992 Nov 4;268(17):2420-5. PMID: 1404801
(http://jama.ama-assn.org/cgi/reprint/268/17/2420?ijkey=d3d27e0bf59a836b2ff7923ef06634c6304b1c75&keytype2=tf_ipsecsha)
(B) Montori VM, Guyatt GH. Progress in evidence-based medicine.
JAMA. 2008 Oct 15;300(15):1814-6. PMID: 18854545
(http://jama.ama-assn.org/cgi/content/full/300/15/1814)**Since EBM
advocates that medical decisions should proceed from application of
the current best evidence, an appreciation of how to evaluate, or
grade, evidence is crucial to the application of best evidence in
practice. *Conceptually, evidence starts simply with what is
observed. Every individual observation is an isolated piece of
evidence. To generate higher quality evidence, however, it is
important to compile, organize, and evaluate those individual
observations in a systematic way. Thus, while an anecdotal
observation constitutes evidence regarding a single event, a more
organized compilation of several observed events can constitute a
case series, a higher level of evidence. An even more organized way
to evaluate an event or an intervention is to use systematic
observation, as in an uncontrolled or controlled trial. A
meta-analysis provides even higher quality evidence by
systematically grouping together and synthesizing the results of
multiple trials. Thus, the more systematic an approach that is
taken to gathering and organizing evidence, ranging from the
individual anecdote up to the meta-analysis of controlled trials,
the higher quality the evidence.
*With the growing appreciation for and application of EBM,
efforts have also been made to provide appropriate guidance for
clinicians seeking to understand the quality of evidence behind
published recommendations and guidelines. The United States
Preventive Services Task Force provided one of the first
classifications of evidence, with the 1989 publication of the
original Guide to Clinical Preventive Services. (A) The 5 level
system presented to grade USPSTF recommendations was designed to
reflect the quality of evidence underlying each of the preventive
interventions discussed. (B) Subsequent years have seen a
proliferation of evidence-rating schemes and classifications, all
seeking to provide some guide to assessing and ranking the quality
of published medical evidence. Evidence rating systems have been
published by the Centre for Evidence-Base medicine in Oxford, UK,
the American College of Cardiology, the American Academy of Family
Physicians, and many other groups. While some early evidence-rating
schemes erred on the side of too much detail and too many
categories and sub-categories, more recent rating systems have
focused on practicality and ease of understanding in clinical
practice. The most recent comprehensive approach to providing a
unified evidence rating system is the GRADE approach, (C) under
development by the GRADE working group. (D)
(A) U.S. Preventive Services Task Force. Guide to clinical
preventive services: an assessment of the effectiveness of 169
interventions. Baltimore: Williams & Wilkins, 1989.
(B) Woolf SH and Atkins D. The evolving role of prevention in
health care: Contributions of the U.S. Preventive Services Task
Force. Am J Prev Med 2001;20(3S):13-20 .
(C) Guyatt GH, Oxman AD, Vist GE, Kunz R, Falck-Ytter Y,
Alonso-Coello P, Schnemann HJ; GRADE Working Group. GRADE: an
emerging consensus on rating quality of evidence and strength of
recommendations. BMJ. 2008 Apr 26;336(7650):924-6. PMID: 18436948
(http://www.bmj.com/cgi/content/full/336/7650/924)
(D) http://www.gradeworkinggroup.org/*The United States
Preventive Services Task Force (USPSTF) provides 4 grades of
recommendations, depending on the certainty that an intervention or
preventive measure is more likely to cause harm or benefit. USPSTF
also gives an I rating to interventions for which it is felt the
evidence is insufficient to balance risk vs benefit. (A)
(A) USPSTF Grade Definitions. (available at:
http://www.ahrq.gov/clinic/uspstf/grades.htm)*The GRADE system for
rating evidence is currently under development by the GRADE working
group. (A) This system is designed primarily to be used by authors
of guidelines, and software is also being developed to guide use of
this system in evidence appraisal, but an overview of the
principles underlying GRADE is illustrative of the issues that need
to be considered in evidence rating. (B)
http://www.gradeworkinggroup.org/
Guyatt GH, Oxman AD, Kunz R, Falck-Ytter Y, Vist GE, Liberati A,
Schnemann HJ; GRADE Working Group. Going from evidence to
recommendations. BMJ. 2008 May 10;336(7652):1049-51. PMID:
18467413
*While evidence-classification and rating may seem a daunting
challenge, the basic premise is that the more systematic the
observations that are available (eg, RCT instead of just a case
series) the better the quality of evidence. And, since EBM seeks to
apply the current best evidence it is important to see for the
highest quality studies that are available to address a given
clinical question.
***In order to decide what to do in practice, we also need to
know how well know when we are there that is, what kind of outcomes
do we seek? Medical outcomes can be broadly grouped into 3
categories. Some outcomes (eg, blood pressure or cholesterol
levels) are merely surrogate markers of disease. We measure these
surrogate markers because we think they tell us something
prognostically about the expected course of a persons disease
process, but they do not directly impact how a patient feels from
day to day. Others measure actual stage or extent of disease (eg,
the stage of a diabetic ulcer, or the angiographic extent of
disease). These may have a more direct bearing on a patients
quality of life or extent of suffering, but still do not provide
direct measures of long-term quality of life. The most important
outcomes for guiding medical decisions are those that affect how
patients feel and the quality of their lives that is,
patient-oriented outcomes such as mobilty, suffering, longevity,
and other considerations that bear directly on how a patient
experiences his or her quality of life. In short, patient oriented
outcomes have primarily to do with long-term morbidity or
mortality. (A)
(A) Slawson DC, Shaughnessy AF, Ebell MH, Barry HC. Mastering
medical information and the role of POEMs--Patient-Oriented
Evidence that Matters. J Fam Pract. 1997 Sep;45(3):195-6. PMID:
9312554An even simpler way to break down the types of outcomes that
may be considered is into disease oriented outcomes such as blood
sugar, blood pressure, flow rate, coronary plaque thickness, or
patient oriented outcomes such as reduced morbidity, reduced
mortality, symptom improvement, improved quality of life, or lower
cost. (A)
(A) Ebell MH, Siwek J, Weiss BD, Woolf SH, Susman J, Ewigman B,
Bowman M. Strength of recommendation taxonomy (SORT): a
patient-centered approach to grading evidence in the medical
literature. Am Fam Physician. 2004 Feb 1;69(3):548-56. PMID:
14971837 (http://www.aafp.org/afp/20040201/548.html)In applying
evidence regarding patient-oriented outcomes, it is also important
to work collaboratively with the patient to determine which
outcomes are most important to the patient, as this will guide the
decision as to which interventions to pursue. Three examples
illustrate this point: 1) Topical antibiotics for bacterial
conjunctivitis may improve early and late resolution rates, but
nearly all cases ultimately have complete remission. (A) 2) Digoxin
for symptomatic heart failure provides no significant difference in
mortality but is associated with lower rates of hospitalization and
of clinical deterioration. (B) 3) Long-acting beta-2 agonists for
asthma are effective in reducing symptoms but may increase
mortality or exacerbations. (C) Thus, it is vital to discuss the
desired target outcome with a patient when deciding how to apply
evidence to a specific patients situation.
Sheikh A, Hurwitz B. Topical antibiotics for acute bacterial
conjunctivitis: Cochrane systematic review and meta-analysis
update. Br J Gen Pract. 2005 Dec;55(521):962-4. PMID: 16378567Hood
WB Jr, Dans AL, Guyatt GH, Jaeschke R, McMurray JJ. Digitalis for
treatment of congestive heart failure in patients in sinus rhythm:
a systematic review and meta-analysis. J Card Fail. 2004
Apr;10(2):155-64. PMID: 15101028Cates CJ, Cates MJ. Regular
treatment with salmeterol for chronic asthma: serious adverse
events. Cochrane Database of Systematic Reviews 2008, Issue 3. Art.
No.: CD006363. DOI: 10.1002/14651858.CD006363.pub2.*The Strength of
Recommendation Taxonomy is one system of evidence grading,
developed by a collaboration among family medicine editors, that
seeks to provide a user-friendly approach to classifying evidence
in terms of both evidence quality, and the degree to which it bears
on patient-oriented outcomes. (A)
(A) Ebell MH, Siwek J, Weiss BD, Woolf SH, Susman J, Ewigman B,
Bowman M. Strength of recommendation taxonomy (SORT): a
patient-centered approach to grading evidence in the medical
literature. Am Fam Physician. 2004 Feb 1;69(3):548-56. PMID:
14971837 (http://www.aafp.org/afp/20040201/548.html)*Clinicians
striving to practice EBM, applying the best current evidence to
patient care, will still be faced (sometimes frequently) with the
task of reconciling competing or conflicting recommendations.
Oxman, Glasziou and Williams provide some helpful suggestions for
issues to consider when trying to make clinical sense out of
seemingly conflicting evidence or recommenations. Questions to
consider regarding the evidence presented include: Were the
clinical questions different? Were different studies considered?
Were the results analyzed differently? Was the quality of evidence
assessed differently? Questions of outcome or consequences that
need to be considered include: Did the effect estimates for
important outcomes differ? Did judgments about evidence quality
differ? Were health consequences weighed differently? Were economic
consequences considered differently?
(A) Oxman AD, Glasziou P, Williams JW Jr. What should clinicians
do when faced with conflicting recommendations? BMJ. 2008 Nov
28;337:a2530. doi: 10.1136/bmj.a2530. PMID: 19042938
**Increasing emphasis on evidence-based medicine has also
brought to the fore the potential tension between the presumed
autonomy of the individual practitioner or physician, and the
recognized value of informed decision making on the part of
patients. Evidence and information systems can help educate both
patients and physicians on the potential benefits and risks of
different courses of action, but engaging patients in this process
can seem threatening to physicians who are used to being autonomous
professionals given full charge for the patients care. A recent
JAMA editorial highlighted some key principles for addressing this
tension:Physicians must recognize the role of being the patients
agent in helping make informed decisions to maximize benefit at
reasonable costMedical students and residents should be educated to
approach care as the patients agent in making informed decisions,
rather than solely as an autonomous decision makerThe evidence for
and approach to developing standards should be standardized.
(A) Mathews SC, Pronovost PJ. Physician autonomy and informed
decision making: finding the balance for patient safety and
quality. JAMA. 2008 Dec 24;300(24):2913-5. PMID: 19109120 In
summary:Evidence based medicine is the conscientious, explicit, and
judicious use of current best evidence in making decisions about
the care of individual patients. Evidence is essentially about
observation, but high-quality evidence requires systematic
observationEvidence is best applied in the pursuit of
patient-oriented outcomes
***
