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Evidence Based Medicine
Evidence-based medicine
relies on rigorous scientific research to help clinicians and
patients make decisions about diagnosis and care. It is also a
basis for systematic changes to health care systems intended to
improve the quality of health care services in ways that improve
patient outcomes. Evidence-based medicine is distinguished, at
least in part, by the use of:
- Efficacy and
effectiveness trials - typically of a single intervention,
e.g. use of disease-modifying antirheumatic drugs (DMARDs).
- Meta-analysis
- a quantitative method of obtaining an overall estimate for
effect of medical interventions (Hennekens
and Buring, 1987), usually undertaken when the results
from a single study are insufficient, e.g., because there is
a very small number of patients involved or the study design
is inadequate.
Clinical trials and
health services research studies often fall into one of two categories,
efficacy trials or effectiveness trials, which are compared and
contrasted below.
Table
3.1
| Characteristic
| Efficacy
Trials
| Effectiveness
Trials
|
|---|
| Focus
of Study | Whether
treatment works in controlled setting | Whether
treatment works in real world setting |
| Internal
validity | Higher | May
be lower |
| Generalizability | Lower
(ideal conditions, e.g. perfect compliance, difficult,
if not impossible, to replicate) | Higher,
but intervention may be difficult to replicate |
|
In effectiveness trials
there may be less control over who receives a study drug or intervention;
so the important consideration is whether the treatment does more
good than harm to those who are offered and accept the treatment
(Fletcher et al., 1988). Effectiveness
trials may be further sub-divided into:
- Those that assess
the effectiveness of a single intervention delivered under real-world
conditions (Simon,
Wagner, Von Korff, 1995), versus
- Evaluations of health
care system innovations that may include a set of interventions
delivered via changes in the organization and delivery of patient
care (Von
Korff et al, 1987).
Meta-analysis uses
data from multiple studies that include the same intervention
(e.g. Cox-2 inhibitors for rheumatic pain) and similar patient
groups to derive an overall effect. These are useful, for example,
in pain studies, which tend to include smaller numbers of patients.
Meta-analysis is only
beginning to be applied to health care system changes that may
consist of multi-faceted interventions. At present, it is unclear
the extent to which methods of meta-analysis can be applied to
evaluation of health care system change. Given that the optimal
management of chronic symptoms is likely to require multi-component
interventions that are fully integrated into the delivery of health
care, development of methods for synthesizing evidence on the
effectiveness of multi-faceted changes in health care systems
is a critically important issue.
An
Example of Evidence Based Medicine
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The
Cochrane Collaborative
http://www.cochranelibrary.com/enter
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| The
Cochrane Collaborative is an international effort to
provide and maintain up-to-date systematic reviews of
all relevant randomized trials and seminal research
based on medical interventions. Studies are critically
appraised and include meta-analyses for each intervention
using both published literature (MEDLINE, EMBASE, PSYCHLIT,
etc.) and unpublished reports. The Cochrane Collaborative
web site contains over 500 systematic reviews, including
those for rheumatic conditions and their symptoms. |
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