Lecture 03

Question 1

What is hierarchy of evidence?

Answer 1

-) Rank the scientific value of different kinds of evidence
-) Consider the strength of evidence

Question 2

Name the 5 levels of simple hierarchy of intervention evidence.

Answer 2

Level 1: Systematic review of RCTs
Level 2: RCTs
Level 3: other CONTROLLED clinical trials
Level 4: observational studies (cohort and case control)
Level 5: Case studies, personal opinion, bench studies, anecdote

Question 3

Name the 5 levels of evidence in CEBM.
(1a, 1b, 2a, 2b, 3a, 3b, 4, 5)

Answer 3

1a. Systematic review and meta-analyses of RCTs
1b. Individual RCT (narrow CI)

2a. Systematic review of cohort studies
2b. Individual cohort study + low quality RCT

3a. Systematic review of case-control studies
3b. Individual case-control studies

4. Case-series + poor quality cohort and case-control studies
5. Expert opinion without explicit critical appraisal + bench research

Question 4

What is RCT?

Answer 4

-) Compare >= 2 treatment conditions
-) Randomly allocate participants to groups
-) Control for known sources of study bias

Question 5

Name 2 interpretations of treatment effects of RCTs.

Answer 5

1. Small treatment effects -> undetectable, need a large sample
2. Varied treatment effects between people -> unreliable inferences from single case studies

Question 6

RCTs are designed to control for change due to ?

Answer 6

1. Spontaneous recovery unrelated to treatment
2. Maturation
3. Unexpected things (e.g. divorce)

Question 7

What are the essential features of RCTs?

Answer 7

-) Randomly allocate participants to treatment groups with blinding
-) Clear definition of population (where is sample drawn) -> only generalise to the population
-) Clear definition of treatments (*manualized)
-) Clear definition of outcome measures

Question 8

What is a single blind trial?
It eliminates (?) effect.
Disadvantage?

Answer 8

-) Researcher knows but patient does not（淨係blind patient）
-) Eliminates placebo effect
-) Observer bias is possible

Question 9

What is placebo effect?

Answer 9

You think you have the improvement but no improvement actually.

Question 10

What is a double-blind trial?

Answer 10

-) Clinician, patient, assessor do not know which group the patient was.

Question 11

What is intention-to-treat analysis?

Answer 11

-) analyses within the allocated group
-) regardless of whether they experience the intended intervention

Question 12

List 3 limitations of RCTs.

Answer 12

1. Treatment inferior to current treatment -> unethical
2. Failure to perform trials -> harmful treatments
3. Difficult to recruit clinicians to experiment with alternatives
4. Costly and time consuming
5. Needs preliminary evidence
6. Appreciation of size of treatment effect

Question 13

List 2 benefits of RCTs.

Answer 13

1. Cause-effect relation
2. Cost-effectiveness