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L2a - Types and Levels of Evidence Ask a question - Convert information…
L2a - Types and Levels of Evidence
Ask a question
- Convert information need into an answerable clinical question
Acquire the information
- Track down the best evidence for answering the question
Appraise the articles found
- Critically appraise the evidence for validity, impact & applicability
Apply the information
- Integrate the evidence into your clinical decision making
Audit/Assess
- Evaluat steps 1-4 and seek ways to improve next time
Clinical Research vs Basic Science
Require the same approaches, but with basic science, the disease or intervention is assessed in a “created” environment while clinical research investigates diseases and/or interventions in human patients
Observational or Experimental Study?
Did the investigator Assign Exposures?
Yes
Experimental Study
Random Allocation?
No
Non-Randomised Controlled Trial
Yes
Randomised Control Trial
Is the gold-standard in clinical research
Designed specifically to minimise bias
Is the equivalent of a controlled experiment in basic science
Participants are randomized into two (or more) groups, and each group receives a different intervention.
Hallmark Feature
Participants assigned to varying
"treatments" by chance
- supposedly reduces influence of arbitrary factors biasing results
Participants blind to their treatment
Sometimes trial staff blinded to which treatment they have administered to whom
Addresses Interventional/Therapeutic Questions
Pros
If properly designed, can be free of bias and thus is statistically robust (this means that it can detect small or moderate effects, which other designs can’t do!)
Cons
While it has internal validity, it may not be externally valid (this means while it will do what it sets out to do, the outcome may not hold up outside of the study group)
This is due to prescribed inclusion and exclusion criteria for study volunteers
Sometimes, you just can’t do an RCT – Ethical concerns/issues
Can get expensive…. At least when we’re talking science and medicine…..
RCT Eliminating Bias
Placebo Controlled
Used to support the blinding process
Participants in control group administered a sham intervention
Can be
passive
or
active
Passive placebo
– mimics administration only
Active placebo
– mimics side effects of intervention
No
Observational Study
Comparison Group?
No
Discriptive Study
Yes
Analytical Study
Direction Between Exposure and Outcome
Exposure <= Outcome
Case Control Study
Population selected based on
outcome
and traced back to exposures using retrospective data
3 more items...
Exposure and outcome exist at the same time
Cross-Sectional Study
Measure a population at a particular point in time (“snapshot”), in order to detect a particular outcome
3 more items...
Exposure => Outcome
Cohort Study
An observational study where participants are followed over time
(longitudinal study)
Best way to identify the icidence and relative risk of a disease
Can be slow to yield results
5 more items...
Qualitative Studies
The name given to a group of designs which focus on patientoriented
outcomes
Uses;
Interviews
Focus groups
Participant observation
PROS
Value in understanding personal experience and how it impacts the patient and practitioner experience
bridge the gap between scientific evidence and clinical practice
Asthma
Doctors were unaware that patients viewed astham treatment negativey consciously chose not to adhere to treatment
Case Study
A study describing a patient or small group of patients affected by a specific disease, or exposed to a factor (eg. an intervention)
Least publishable - no control
=> Hypothesis Generating
Prompt further study
