Levels Of Evidence

Question 1

What are the levels of evidence

Answer 1

1 - meta analysis or systematic review
2 - RCT
3 - cohort studies 
4 - case control studies
5 - case series or case reports 
6 - editorials, expert opinions, animal studies

Question 2

What are the criticisms surrounding using a heirachy system for evidence

Answer 2

Lack of evidence that EBM patients do better than others
Limited applicability to individual patients who are all so different
Threatens doctor autonomy
Over reliance on empiricism?? (Whatever this means)

Question 3

Why is it hard to get evidence in prehospital medicine

Answer 3

Chaotic environment with lots of confounders
Limited applicability to other settings so limited funding
Ethics and informed consent
Small numbers of patients

Question 4

What is selective reporting and how can we overcome it

Answer 4

Journals publishing depending on the results - overcome it by them agreeing to publish based on methodology before the results are available

Question 5

Why don’t we use the evidence that is available

Answer 5

We’re not robots - ethically would feel wrong to not do something even if evidence suggests it doesn’t work and legally doing something sounds better than nothing even if no evidence it works
Availability bias - we rely on immediate past examples that come to mind to make decisions (these examples are often the most recent)
Biological plausibility - if it seems biological plausible we’ll probably try it even if no evidence
Emotional involvement

Question 6

What is a meta analysis

Answer 6

A systematic review (systematic search and appraisal of literature) that uses quantitive methods to summarise results

Question 7

What is a randomised control trial

Answer 7

Patients randomised to either control or experimental group and are followed up for outcome

Question 8

What is a cohort study

Answer 8

2 groups identified, 1 which had the exposure and 1 which didn’t. They are then followed for outcome

Question 9

Compare retrospective cohort study and case control study

Answer 9

Retrospective cohort: exposures defined before looking at the existing outcome to see if exposure is a RF for outcome
Case control study: identifies patients with and without the outcome then looks to see what their exposures are. Outcome measure is OR