Evidence-Based Medicine (EBM) - the fundamentals Flashcards
Evidence-Based Medicine - definition
Evidence based medicine is the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients. (Sackett DL et al, 1996)
Why use evidence based medicine:
Ensure medicines sold are of high quality, safety and efficacy
Basis for the recommendations we make to patients and other health professionals through pharmacy services
It is essential that pharmacists are available to retrieve, appraise and apply research evidence as the basis for clinical decision making
Sources of evidence =
- secondary
- primary
- no design
- not involved with humans
Secondary source
1) Randomised controlled trial, prospective tests treatment
Experimental = pre-appraised, or filtered studies
Primary source
2) Cohort studies - Prospective, cohort has been exposed to a risk.
Observe for outcome of interest.
3) Case control studies - Retrospective, subjects have the outcome of interest, looking for risk factor
Non-experimental = observational studies
No design sources
4) Case report or Case series
5) Narrative reviews, expert Opinions, editorials
Not involved with humans sources
Animal and laboratory studies
e.g. rat, guinea pig
What examples are there of secondary studies?
a) Clinical practice guidelines
b) Meta-analysis systematic reviews
Problems with animal and lab study?
Its application is limited considering the difference between human and animal physiology
Experiments are undertaken in a highly controlled environment
Cross-sectional studies
An observational study design where outcomes and exposures are measured concurrently.
Participants are selected based on set inclusion and exclusion criteria.
How does cross-sectional studies work?
Include a target population and take a study sample (smaller group) - Gather data at one time on both exposure AND outcome
What are the 4 variations of outcomes in cross-sectional study?
Exposed and outcome present
Exposed and no outcome
Unexposed and outcome present
Unexposed and no outcome
Case-control study design;
Retrospective in nature
Case-control study design
ADVANTAGES
Less expensive
Easier to do and take less time
Useful when obtaining follow-up data that is difficult to obtain due to the nature of population being studied
More efficient if the disease is rare
This design may be the only ethical way to evaluate something
Case-control study design
DISADVANTAGES
Potential recall bias
Subject to selection bias
Generally do not allow investigators to calculate an incidence or absolute risk
Cohort study….prospective
Almost always prospective, but sometimes can be retrospective cohort studies
Cohort study
ADVANTAGES
Can more clearly show the time of exposure and development of the outcome because the subjects are without the disease at baseline.
Allows for evaluation of more than one outcome as it relates to an exposure
Allows for the calculation of the incidence
Cohort study
DISADVANTAGES
Can be expensive and time consuming because of needing to follow a large number of people
Loss of follow up can begin to introduce bias
May not be good for rare diseases
Randomized Controlled Trial (RCT)
ADVANTAGES
Considered the gold standard
This design allows for washout of most population bias
Reduced influence by confounders
Reduced variability in the outcome(s)
Easier to blind patients than observational studies
Randomized Controlled Trial (RCT)
DISADVANTAGES
Generally more time consuming
Tend to be more expensive
Systematic Review
- a literature review that is designed to locate, appraise and synthesize the best available evidence relating to a specific research question to provide informative and evidence-based answers.
- info can then be combined with professional judgment to make decisions about how to deliver interventions or to make changes to policy.
Meta-Analysis
use of statistical methods to summarise the results of independent studies.
By combining information from all relevant studies, meta-analysis can provide more precise estimates of the effects of health care than those derived from the individual studies included within a review
Meta- analysis
ADVANTAGES
Objective evaluation of research findings
Meta-analysis
DISADVANTAGES
Not all topics have sufficient research evidence to allow a meta-analysis to be conducted
Guidelines (e.g., NICE guidelines)
ADVANTAGES
Are on topic of relevance to population (usually determined by NHS England or the Department of Health and Social Care).
Thorough and transparent development process to ensure fairness.
Representative stakeholders involved in the process.
Guidelines are developed using thorough literature reviews of many RCTs and other forms of evidence.
Directly applicable to patients.
Often take into account a huge number of potential treatments and drug classes, e.g. type 2 diabetes guidelines.
Complex issues simplified.
Regularly reviewed.
Take into account cost considerations.
Guidelines (e.g., NICE guidelines)
DISADVANTAGE
Resources
Conflict of interest?
Key terms in epidemiological calculation
Endpoints
Absolute risk reduction (ARR)
Relative risk reduction (RRR)
Number needed to treat (NNT)
Number needed to harm (NNH)
What is an Endpoint?
- endpoint is an event or outcome that can be objectively measured in a study.
- endpoints should be pre-defined and, ideally, sufficiently powered.
Primary endpoint/s:
the main result/s that is measured at the end of a study to see if a given intervention was effective
– needs to be clinically relevant and must always be powered
Secondary endpoints:
these are additional events of interest, but which the study may not be specifically powered to assess
Patient-oriented endpoints (POEs)
An ideal endpoint should be a valid and applicable measure of how a patient feels, functions or survives.
What does POEs measure?
this directly, e.g. number of fractures, strokes, myocardial infarction, deaths, caner recurrence, pain levels, number of migraines, etc.
Advantages of POEs
measures of true patient benefit, clinically meaningful, clinical certainty
Disadvantages of POEs
need large sample size, longer trial duration, more expensive, delay in potentially beneficial medicines coming to market
Disease oriented endpoints (DOEs)
known as “surrogate” endpoints: do not directly measure how a person feels, functions or survives, but which should be so closely associated with a clinically meaningful endpoint that they are taken to be a reliable substitute for them, e.g. blood sugar, blood pressure, cholesterol levels, bone mineral density.
Advantages of DOEs
smaller sample size, shorter trial duration, less expensive, expediates medicines to market.
Disadvantages of DOEs
may not relate to clinically meaningful outcomes, may not change at all stages of disease, may predict that harmful treatments are effective.
Examples of Disease vs. Patient Oriented Endpoints
DOE: Beta-carotene and vitamin E are good antioxidants
POE: Neither vitamin prevents cancer or cardiovascular disease
DOE: Anti-arrythmic drug X decreases the incidence of premature ventricular contractions on ECGs
POE: Anti-arrythmic drug X is associated with an increase in mortality
