IT IS A SIMPLE NOTES FOR UNDERSTANDING EVIDENCE BASED MEDICINE

1. Presented by KRISHNA M 4TH PHARM D

2.  One of the major changes in the teaching and practice of medicine has been
the rapid growth in evidence-based medicine (EBM), which is reflected in
this new edition by now having its own subsection. As Paul Glasziou and
colleagues have argued ‘a 21st century clinician who cannot critically read a
study is as unprepared as one who cannot take blood pressure or examine
the cardiovascular system. Evidencebased medicine, previously referred to
as clinical epidemiology, has grown rapidly over the last 20 years, partially as
a result of better-quality research, systematic methods to accumulate and
summarise these data, and easy access to highquality databases such as the
Cochrane collaboration or EBM-based guidelines that allow health
professionals to quickly access evidence when considering patient
management.

3.  ‘the conscientious, explicit and judicious use of current best evidence
in making decisions about the care of individual patients and
improving the health of populations

4.  PROVIDE BETTER INFORMATION.
 BETTER PATIENT OUTCOME.
 GENERALIZE INFORMATION.
 IT IMPROVES THE EFFECTIVENESS IN THE CLINICAL PRACTICE.
 IT INVOLVES IN THE EVIDENCE FOR BETTER DECISION MAKER.

5.  EBM denigrates clinical experience.
 Ignores patient values.
 Promotes an unthinking cookbook approach to medicine .
 A cost-cutting tool .
 An ivory tower research exercise not suited to everyday clinical
practice.
 Leads to therapeutic nihilism in the absence of evidence from
randomised controlled trials Source: Modified from Straus SE,
McAlister FA (2000) Evidence-based medicine: a commentary on
common criticisms

6.  Patient or commissioner/ policy-maker EBM domain
 What is making me feel unwell? Diagnosis
 Will this have any long term consequences? Prognosis
 Why did I get ill? etiology What can you do to help me? Treatment
 Are any interventions worth paying for? (commissioners,
policymakers) Cost-effectiveness

7.  There are several steps in being a EBM practitioner. These are
 (a) formulate a clear question,
 (b) search for the evidence,
 (c) critically appraise the evidence,
 (d) apply the evidence (or not) to the individual patient or population
as appropriate

8.  Study designs should be evaluated according to the hierarchy of
evidence EBM tries to use evidence in an explicit fashion by
quantifying benefits and harms using concepts such as the numbers
need to treat The five EBM domains are diagnosis, prognosis,
aetiology, treatment and cost-effectiveness PICO is a useful acronym to
help formulate clear EBM questions EBM is undertaken according to
the following stages: formulating a question, search for evidence,
appraising evidence and applying the evidence, if appropriate
Generalisability of evidence as well as considering patients’
preferences is important in applying evidence to individuals

9.  Two examples of EBM questions.
 Prognostic question
 Patient A 77-year-old woman with hypertension, and moderate left
ventricular enlargement
 Intervention Presence of nonrheumatic atrial fibrillation
 Comparator Absence of nonrheumatic atrial fibrillation
 Outcomes Risk of stroke risk over a specific time period (5 or 10 years)
(both as relative risk and absolute risk difference)
 Therapy question Patient A 77-year-old woman with nonrheumatic atrial
fibrillation, hypertension, and moderate left ventricular enlargement
Intervention Warfarin therapy Comparator No therapy or aspirin Outcomes
Reduction in stroke risk versus increase in bleeding complications (relative
and absolute risks)

10.  The absence of evidence or only the presence of poor quality
evidence. For example a review of 109 inpatients seen in Oxford for
one month found that for 53% of primary treatments there was trial
evidence to support therapy. In an additional 29% there was
convincing nonexperimental evidence and in 18% there was no
evidence that therapy was better than no therapy (Ellis et al., 1995).
This figure is likely to be less good for some other specialties e.g.
primary care. Such absence of evidence does not mean evidence of
absence and should act as a stimulus for future research to help fill
such evidence-based gaps.