| Evidence-based medicine is a medical movement based upon the application
of the scientific method to medical practice, including
long-established existing medical traditions not yet subjected to adequate
scientific scrutiny. According to the Centre for
Evidence-Based Medicine (http://www.cebm.net/), "Evidence-based medicine is
the conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual
patients."
Overview
Using techniques from science, engineering and statistics, such as meta-analysis of the existing literature, risk-benefit analysis
and randomized controlled trials, it aims for
the ideal that all doctors should make "conscientious, explicit, and
judicious use of current best evidence" in making decisions about the care of individual patients.
Evidence-based medicine categorizes different types of clinical evidence and ranks them according to usefulness for guiding a
treatment decision for an individual patient. For example, the strongest evidence is provided by randomized controlled
prospective trials involving similar patients with similar conditions. In contrast, testimonials, hearsay and mystical arguments
have little value as proof because the placebo effect, random events and observer bias distort perceptions.
Practising evidence-based medicine implies not only clinical expertise, but expertise in retrieving, interpreting, and
applying the results of scientific studies, and in communicating the risks and benefit of different courses of action to
patients.
For all its problems, evidence-based medicine has very successfully demoted the ex cathedra statement of the "medical
expert" to the least valid form of evidence and all "experts" are now expected to be
able to reference their pronouncements to the relevant literature.
History
Professor Archie Cochrane was a British medical researcher whose
book Effectiveness and Efficiency: Random Reflections on Health Services (1972) and subsequent advocacy caused increasing
acceptance of the evidence-based medicine concept. Cochrane's work was honoured through the naming of centres of evidence-based
medical research — Cochrane Centres — and an international organisation, the Cochrane Collaboration.
Qualification of evidence
The U.S. Preventive Services Task Force developped the following system to asses quality of medical evidence:
- Level I: Evidence obtained from at least one properly designed randomized contolled trial.
- Level II-1: Evidence obtained from well-designed controlled trials without randomization.
- Level II-2: Evidence obtained from well-desigend cohort or case-control analytic studies, prferably from more than one center or research
group.
- Level II-3: Evidence obtained from multiple time series with or without the intervention. Dramatic results in uncontrolled
could also be regarded as this type of evidence.
- Level III: Opinions of restected authorities, based on clinical experience, descriptive studies, or reports of expert
committees.
Categories of evidence
The U.S. Preventive Service Task Force categorizes medical evidence as follows:
- Level A: Recommendations are based on good and consistent scientific evidence.
- Level B: Recommendations are based on limited or inconsistent scientific evidence.
- Level C: Recommendations are based primarily on consensus and expert opinion.
Criticism of evidence-based medicine
Critics of evidence-based medicine state that doctors were doing these things already, that good evidence is often deficient
in many areas, that lack of evidence and lack of benefit are not the same, and that the more data are pooled and aggregated the
more difficult it is to compare the patients in the studies with the patient in front of the doctor. i.e. EBM applies to
populations, not necessarily to individuals. In The limits of
evidence-based medicine (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11728302&dopt=Abstract),
Tonelli argues that "the knowledge gained from clinical research does not directly answer the primary clinical question of what
is best for the patient at hand." Evidence-based medicine seems to them to discount the value of the case study.
Evidence-based medicine is quickly rising as the 'gold standard' for clinical practice and guidelines. The majority of current
medical and surgical practice, however, does not have a strong literature base supporting it. There are a number of reasons.
First, in some cases, doing randomized controlled trials would be unethical--such as in open-heart surgery. Second, certain
groups have been historically marginalized (women, racial minorities, people with many co-morbid diseases) and thus the
literature is very sparse in areas that does not allow for generalizeability. Third, the types of trials considered 'gold
standard' (i.e. randomized double-blind placebo-controlled trials) are very expensive and thus funding sources play a role in
what gets investigated. For example, the government funds a large number preventive medicine studies trying to improve public
health as a whole, pharmaceutical companies fund studies to demonstrated efficacy and safety of particular drugs. Fourth, the
studies that make it into medical journals may not be representative of studies that are completed or may be misleading due to
conflicts of interest (i.e. publication bias).
[1] (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=14748860&itool=iconabstr)
Thus the array of evidence available on particular therapies may not be well-represented in the literature. Fifth, there is an
enormous range of quality of studies performed and it is difficult to generalize about results.
Large scale randomized control trials are extraordinarly useful for examining discrete interventions with defined medical
conditions involved. The more complex the patient population, the conditions, and the intervention, the more difficult it is to
tease apart effect from random variation. In this way, a number of null studies get published, either because there is
insufficient power to show difference, or because the groups are not well-enough 'controlled.'
The primary problem is that evidence-based medicine is most effective when testing the effectiveness of drugs and may not be appropriate for other forms of treatment, particularly those requiring the active
participation of the patient.
In America, evidence-based guidelines are used as the
basis for denying insurance coverage for treatments which are generally held by physicians to be effective, but for which
randomized, controlled trials have not yet been held.
External links
|
