evidence based medicine - fundamentals

Question 1

What is 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

What are the 5 steps to evidence based practice?

Answer 2

1: ask a question
2: find best evidence
3: evaluate evidence
4: apply information in combination with clinical experience + patient values
5: reflect + evaluate outcome

Question 3

Why use evidence based medicine?

Answer 3

• ensure medicine sold are high quality, safe and efficient

Question 4

What are the five sources of evidence + their levels?

Answer 4

level 1: randomised controlled trial
level 2: cohort studies
level 3: case controlled studies
level 4: case report or case series
level 5: animal and laboratory studies

Question 5

What are some examples of study designs?

Answer 5

• experimental
• observational

Question 6

What are types of experimental study designs?

Answer 6

*animal and laboratory studies
*clinical trials
- controlled trials e.g RCT
- uncontrolled trials

Question 7

What are types of observational study designs?

Answer 7

*Cohort studies
* Case-controlled studies
* cross-sectional studies

Question 8

What are the disadvantages of animal and lab study?

Answer 8

• Its application is limited considering the difference between human and animal
  physiology
• Experiments are undertaken in a highly controlled environment

Question 9

What is a cross-sectional study?

Answer 9

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

Question 10

What are the advantages to case-control study designs?

Answer 10

• 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 11

What are the disadvantages to case-control study designs?

Answer 11

• Potential recall bias
• Subject to selection bias
• Generally do not allow investigators to calculate an incidence or absolute risk

Question 12

What are the advantages to the cohort study?

Answer 12

• 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 13

What are the disadvantages to the cohort study?

Answer 13

*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 14

What are the advantages to the randomised controlled trial?

Answer 14

• 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 15

What are the disadvantages to the randomised controlled trial?

Answer 15

• Generally more time consuming
• Tend to be more expensive

Question 16

What are the advantages of the systematic review?

Answer 16

• Use strategies that reduce biases and
  random errors.
• Provide reliable information about the
  topic being studied
• Identify gap in knowledge to direct
  future research

Question 17

What is the disadvantage to the systematic review?

Answer 17

*Does not allow further analysis of data

Question 18

What is the advantage and disadvantage to meta-analysis?

Answer 18

advantage: Objective evaluation of research findings
disadvantage: Not all topics have sufficient research evidence to allow a meta-analysis to be conducted

Question 19

What are the advantages to guide-lines?

Answer 19

• 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 20

What are the disadvantages to guide-lines?

Answer 20

*resources
*conflict of interest

Question 21

What is an endpoint?

Answer 21

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

Question 22

What is the primary endpoint?

Answer 22

*main outcome to identify effectiveness of intervention
- needs to be clinically relevant

Question 23

What is the secondary endpoint?

Answer 23

not the main outcome but additional events of interest, that the case study may not be specifically out to asses

Question 24

What is a POE? (patient oriented end point)

Answer 24

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

Question 25

What are the advantages to POEs?

Answer 25

measures of true patient benefit, clinically meaningful, clinical
certainty

Question 26

What are the disadvantages to POEs?

Answer 26

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

Question 27

What is a DOEs? (disease oriented endpoint)

Answer 27

also 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

Question 28

What are the advantages to DOEs?

Answer 28

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

Question 29

What are the disadvantages to DOEs?

Answer 29

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

Question 30

What is ARR? (absolute risk reduction)

Answer 30

ARR: the straightforward difference between event rates.
ARR=Risk in the Control Group−Risk in the T
reatment Group

Question 31

What is RRR? (relative risk reduction)

Answer 31

RRR: the difference in event rates expressed relative to what you started with

Question 32

What is the RRR equation?

Answer 32

RRR = (risk in control group-risk in the treatment group / risk in control group) x100%

Question 33

What is NNT? (number needed to treat)

Answer 33

The number of patients who need to receive a specific treatment over a defined period to prevent one additional adverse outcome (or
to achieve one additional positive outcome) compared to a control group or an alternative
treatment

Question 34

What is the formula to calculate NNT?

Answer 34

NNT = 1/ absolute risk reduction (ARR)