Evidence Based Medicine

Doing what is right

Definition Conscientious, explicit, judicious use of

current best evidence in making decisions about care of an individual patient

Involves integrating individual clinical experience with best external evidence from systematic research

Types of EBM Evidence based guidelines- production

of guidelines, policy and regulations to be used at the organizational or institutional level

Evidence based individual decision making- use of available evidence to provide best treatment to an individual patient, by an individual physician

Answering clinical question Formulate a question

Search the literature

Evaluate the literature

Apply available evidence in management

Stratifying evidence Prospective, randomised, double-blind placebo

controlled trial Prospective, randomised double-blind comparative

trial Systematic review- Meta-analysis Prospective controlled trial, without randomisation Sub-group analysis or Retrospective study Uncontrolled trials- Cohort/Case-control studies Case series or case reports Expert opinion

Levels of evidence I- from at least one RCT II- from controlled trials without

randomization, multicentric case-control or cohort studies or uncontrolled trials

III- opinions of respected authorities, based on clinical experience or reports of expert committees

Categories of recommendation A- good scientific evidence that

benefits >>> potential risks B- fair scientific evidence that

benefits >> potential risks C- fair scientific evidence that

benefits > potential risks D- fair scientific evidence that

risks > benefits I- insufficient scientific evidence

Clinical trial Study done to allow safety and efficacy

data to be collected for health interventions

Needs a protocol Investigators recruit patients, administer

treatment, collect data over specified time period

Data is analysed using statistical tests

Types of Clinical trials Prevention trial Screening trial Diagnostic trial Treatment trial Quality of life trial Compassionate use trial

Terms Randomised- subjects are randomly

assigned

Double-blind- subjects and researchers do not know the treatment being given, to prevent any bias

Placebo controlled- use of placebo helps isolate the effect of study treatment

Phases of Clinical trials Pre-clinical studies- in-vitro or animal

studies to obtain preliminary efficacy, toxicity and pharmacokinetic data

Phase 0- subtherapeutic doses to few patients to get pharmacokinetic and pharmacodynamic data

Phases- contd. Phase I- assesses safety, tolerability and

dose range in healthy volunteers Phase II- assesses dose and efficacy in a

larger group of volunteers and patients Phase III- randomised controlled

multicenter trials on large patient group for effectiveness of the treatment

Phase IV- post-marketing safety surveillance

Statistical terms p-value- <0.05 considered significant Relative risk- risk of an event relative to

exposure Hazard ratio- ratio between the predicted

hazard for members of two groups Odds ratio- ratio of the odds of an event

occurring in one group to the odds of it occurring in another group

Statistical terms- contd. SeNsitivity- probability of a positive test

result in someone with target disease i.e. true Positive

SPecificity- probability of a negative test result in someone without the disease i.e. true Negative

Statistical terms- contd. Number needed to treat (NNT)-

number of patients needed to treat to prevent one clinical event

NNT= 1/absolute risk reduction

Number needed to harm (NNH)- for harmful effects of the treatment

Quality of Clinical trials Clearly defined eligibility criteria and have

minimal missing data Results must be generalizable in clinical

practice Adequate follow-up for defined outcomes to

occur and to detect differences between arms of study

Sufficient number of patients to detect a significant difference

Limitations Ethical issue of offering or not, of an unproven

treatment Cost of trial and consequent source of funding Generalizability, comparability and extrapolation of

results Publication bias Use for rationing resources by economists,

policymakers and managers Availability of credible evidence Applying statistics to individuals