Systematic review

Question 1

What are the four purposes of a systematic review?

Answer 1

1. Collate and summarise evidence
2. Permit evidence-based recommendations about useful treatments
3. Identify gaps and shortcomings in our evidence
4. Generate new hypotheses to be explored

Question 2

What are 6 requirements in the making of a systematic review?

Answer 2

1. Clearly stated set of objectives (questions)
   - e.g. how effective is CBT for depression in adults compared to antidepressant medication?
2. Pre-defined eligibility criteria for studies
3. Systematic literature search strategy
   - identify relevant papers for review and analysis
4. Explicit, reproducible methodology
5. Assessment of the quality of the study
   - synthesise the evidence and arrive at answers to starting question
   - higher quality study -> higher importance/weight
6. Systematic presentation and synthesis of studies and findings
   - tables and graphics

Question 3

Why does a systematic review requires explicit and reproducible methodology?

Answer 3

• Increases the reliability of the review process itself

- Minimizes bias on the part of the reviewer

Question 4

What is the result of methodological shortcomings in RCTs?

Answer 4

Downgraded quality of the evidence

-> assess the quality before drawing conclusions

Question 5

What is the GRADE of a study?

Answer 5

Grading of Recommendations, Assessment, Development and Evaluation (GRADE):
- 0 = study should be disregarded completely

• 1 = Very low quality (e.g. case series/report, downgraded observational study)
• 2 = Low (e.g. observational study, downgraded randomised trial)
• 3 = Moderate (e.g. upgraded observational study, downgraded randomised trial)
• 4 = High (e.g. double upgraded observational study, randomised trial)

Question 6

Which limitations of a study can reduce (downgrade) its quality, following the GRADE?

Answer 6

• Lack of blinding
• Randomisation problems
• Small sample size, very variable results
• Poor participation retention
• Missing or incomplete data
• Subjective outcomes, selective reporting of results

Question 7

Which factors of a study can increase (upgrade) its quality, following the GRADE?

Answer 7

• Designed to minimize bias
• Large effect sizes (treatment effect)
• Systematic relationships between ‘dose’ and response (clinical outcome)

-> strong supportive evidence

Question 8

What are meta-analyses?

Answer 8

> Formal statistical approach

> Combine findings to draw an overall conclusion about treatments efficacy
-> together they provide clearer picture

> Overall estimate of the size of the treatment effect
- overall effect measure from various studies

(269 published between 2000-2011 for CBT for depression)

Question 9

What is the purpose of standardised effect sizes?

Answer 9

Allow us to compare the results across studies using different outcomes

Question 10

What are the two formulas for a standardised effect size?

Answer 10

1. Raw mean difference
   = Group B change - Group A change
2. Standardised mean difference
   = mean difference/Standard deviation at baseline

Question 11

How are results characterised with a standardised effect size?

Answer 11

> Zero = no difference following treatment

> Positive (+) = e.g. treatment favours group B

> Negative (-) = e.g. treatment favours group A

Question 12

What are the statistic indexes used for a standardised effect size (standardized mean difference - SMD)?

Answer 12

> Cohen’s index

> Hedges g index

• 0.8 = large effect size
• 0.5 = moderate
• 0.2 = small

Question 13

How do you standardize the effect size with discrete variables such as recovery or relapse?

Answer 13

Relative risk ratio - Risk Ratio (RR):
- relative likelihood that patient will show with events outcome in the active group, relative to the control gap

> Outcome defined in positive way: recovery
- effective treatment = Higher relative risk

> Outcome defined in negative way: relapse
- effective treatment = Lower relative risk

> No differential risk: RR = 1.0

Question 14

In a meta-analysis table, what does the ‘weight’ refer to?

Answer 14

Proportion of the total number of participants in analysis contributed by each study

Question 15

In a meta-analysis, what do the ‘events’ refer to?

Answer 15

The number of patients that show the outcome

Question 16

What did the study of Hollon and colleagues (2014) consist of?

Answer 16

> Cognitive therapy with antidepressant medications

vs. antidepressants alone, on the rate of recovery in MDD
- N = 452
- 3 centres
- goal of treatment was long term
- chronic or recurrent depression
- naturalistic treatment (up to 42 months)

> Outcome criteria:

• remission
• recovery

> Methods:

• divided into low and high severity depression
• randomised to medication alone or CBT with medication
• blind assessment

Question 17

What were the results of Hollon and colleagues’ study (2014)?

Answer 17

• Advantage of CBT x medication is absent in patients with long duration of depression
• Significant advantage in those with shorter duration of depression

=> For patients with chronic depression or less severe symptoms, there was no added benefit in adding CBT to medication, and conversely

Question 18

What did the meta-analysis of Cuijpers and colleagues (2013) show regarding whether CBT is more effective than other psychotherapies not based on the cognitive model?

Answer 18

> Analysis of trials between 1966 and 2011
- N = 46 studies comparing CBT to other psychotherapies

> No significant benefit of CBT compared to other psychotherapies

> Effect size very small

> However, majority of these studies had methodological weaknesses that limited their quality

• > CBT based on cognitive model may not be the only useful approach
• all psychotherapies may share common (non-specific) factors that drive improvement