Evidence-Based Medicine (EBM) - the fundamentals

Question 1

Evidence-Based Medicine - definition

Answer 1

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)

Question 2

Why use evidence based medicine:

Answer 2

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

Question 3

Sources of evidence =

Answer 3

• secondary
• primary
• no design
• not involved with humans

Question 4

Secondary source

Answer 4

1) Randomised controlled trial, prospective tests treatment

Experimental = pre-appraised, or filtered studies

Question 5

Primary source

Answer 5

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

Question 6

No design sources

Answer 6

4) Case report or Case series

5) Narrative reviews, expert Opinions, editorials

Question 7

Not involved with humans sources

Answer 7

Animal and laboratory studies

e.g. rat, guinea pig

Question 8

What examples are there of secondary studies?

Answer 8

a) Clinical practice guidelines
b) Meta-analysis systematic reviews

Question 9

Problems with animal and lab study?

Answer 9

Its application is limited considering the difference between human and animal physiology

Experiments are undertaken in a highly controlled environment

Question 10

Cross-sectional studies

Answer 10

An observational study design where outcomes and exposures are measured concurrently.
Participants are selected based on set inclusion and exclusion criteria.

Question 11

How does cross-sectional studies work?

Answer 11

Include a target population and take a study sample (smaller group) - Gather data at one time on both exposure AND outcome

Question 12

What are the 4 variations of outcomes in cross-sectional study?

Answer 12

Exposed and outcome present
Exposed and no outcome
Unexposed and outcome present
Unexposed and no outcome

Question 13

Case-control study design;

Answer 13

Retrospective in nature

Question 14

Case-control study design
ADVANTAGES

Answer 14

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

Question 15

Case-control study design
DISADVANTAGES

Answer 15

Potential recall bias

Subject to selection bias

Generally do not allow investigators to calculate an incidence or absolute risk

Question 16

Cohort study….prospective

Answer 16

Almost always prospective, but sometimes can be retrospective cohort studies

Question 17

Cohort study
ADVANTAGES

Answer 17

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

Question 18

Cohort study
DISADVANTAGES

Answer 18

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

Question 19

Randomized Controlled Trial (RCT)
ADVANTAGES

Answer 19

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

Question 20

Randomized Controlled Trial (RCT)
DISADVANTAGES

Answer 20

Generally more time consuming

Tend to be more expensive

Question 21

Systematic Review

Answer 21

• 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.

Question 22

Meta-Analysis

Answer 22

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

Question 23

Meta- analysis
ADVANTAGES

Answer 23

Objective evaluation of research findings

Question 24

Meta-analysis
DISADVANTAGES

Answer 24

Not all topics have sufficient research evidence to allow a meta-analysis to be conducted

Question 25

Guidelines (e.g., NICE guidelines)
ADVANTAGES

Answer 25

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. 

Question 26

Guidelines (e.g., NICE guidelines)
DISADVANTAGE

Answer 26

Resources
Conflict of interest?

Question 27

Key terms in epidemiological calculation

Answer 27

Endpoints
Absolute risk reduction (ARR)
Relative risk reduction (RRR)
Number needed to treat (NNT)
Number needed to harm (NNH)

Question 28

What is an Endpoint?

Answer 28

• endpoint is an event or outcome that can be objectively measured in a study.
• endpoints should be pre-defined and, ideally, sufficiently powered.

Question 29

Primary endpoint/s:

Answer 29

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

Question 30

Secondary endpoints:

Answer 30

these are additional events of interest, but which the study may not be specifically powered to assess

Question 31

Patient-oriented endpoints (POEs)

Answer 31

An ideal endpoint should be a valid and applicable measure of how a patient feels, functions or survives.

Question 32

What does POEs measure?

Answer 32

this directly, e.g. number of fractures, strokes, myocardial infarction, deaths, caner recurrence, pain levels, number of migraines, etc.

Question 33

Advantages of POEs

Answer 33

measures of true patient benefit, clinically meaningful, clinical certainty

Question 34

Disadvantages of POEs

Answer 34

need large sample size, longer trial duration, more expensive, delay in potentially beneficial medicines coming to market

Question 35

Disease oriented endpoints (DOEs)

Answer 35

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.

Question 36

Advantages of DOEs

Answer 36

smaller sample size, shorter trial duration, less expensive, expediates medicines to market.

Question 37

Disadvantages of DOEs

Answer 37

may not relate to clinically meaningful outcomes, may not change at all stages of disease, may predict that harmful treatments are effective.

Question 38

Examples of Disease vs. Patient Oriented Endpoints

Answer 38

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