Systematic review and meta-analysis

Question 1

Systematic review

• Definition
• Aims

Answer 1

Comprehensively identifies, evaluates and synthesises from multiple primary studies on a given topic, using strict criteria.

Aims

• Systematic
• Explicit: objectives, materials and methods clearly stated
• Reproducible.

Question 2

Advantages of systematic review

Answer 2

• Reduces bias
• Can be reproduced
• Resolves controversy between conflicting studies.
• Identifies gaps in current research
• Reliable bias for decision making.

Question 3

Narrative/ Literature review

- Definition

Answer 3

Commentary produced by content expert.

Question 4

Compare systematic review from narrative review

• Bias
• Criteria
• Search for material
• Methods
• Replicability

Answer 4

Bias
- Narrative more bias as review is dependent on author’s inclination. Whereas systematic has scientific approach.

Criteria
- Narrative criteria can evolve whereas systematic is determined from onset.

Search for material
- Narrative searches any database whereas systematic has comprehensive search for relevant articles.

Methods
- Not specified in narrative, in systematic, it is explicitly said.

Replicability
- Cannot be reproduced in narrative, whereas it can for systematic.

Question 5

Steps for performing a systematic review

Answer 5

1. Formulate a good question.
2. Comprehensive database search.
3. Unbiased selection and abstraction
4. Critical appraisal of selected studies.
5. Synthesis of data and interpretation of results.

Question 6

Formulation of question for systematic review.

Answer 6

Using PICO(S/T)
- When intervention/ comparison group is included

Using SPIDER
- When there is no intervention/ comparison.
- Includes surveys, qualitative studies.
S- Sample
PI- phenomenon of interest
D- Design
E- evaluation
R- Research type

Question 7

Comprehensive database search

Answer 7

Inclusion criteria: types of studies that will be included, plus the dates and language of publication.
- Use one type of study, i.e RCTs.
- Decide key words to search.
- Use comprehensive database.
- Use tools to appraisal the studies.
- Report using PRISMA.
Exclusion: Studies that will not/ should not be included.

Question 8

Limitations of systematic review

Answer 8

• Results may be inconclusive
• May be no trials or evidence
• Trials may be poor quality
• Practice does not change

Question 9

Meta-analysis definition

Answer 9

Statistical combination of at least 2 studies to produce a single estimate of the effect of health care intervention.

Can be done as part of a systematic review.

Results are commonly displayed as forest plots.

Question 10

Strengths of meta-analysis

Answer 10

Pools results from different trials= effect of bigger sample seen

• Different results from different settings can be compared
• Results of each study, weighted for sample size.

Question 11

Limitations of meta-analysis

Answer 11

• Heterogenicity- difficult to combine studies that measure things different.
• Publication bias
• A lot of effort and subject-areas expertise
• Mechanics of statistics may obscure theory.

Question 12

Hierarchy of evidence [5]

Answer 12

1. Meta-analysis + systematic review
   - Systematic review= narrative of findings from multiple studies
   - Meta-analysis= statistical evaluation
2. RCTs
   - Tightly controlled conditions, assesses efficacy
3. Observational studies: subject to bias but reflective of real life= effectiveness
   - Cohort
   - Case-control
   - Cross-sectional
4. Animal in virto studies
   - Has tightly controlled conditions but not reflective of real life conditions like observational studies.
5. Case reports, narratives