Meta analysis

Question 1

What is the importance of meta-analyses? (3)

Answer 1

A primary study:

• May not have a sufficient sample size of power
• Cannot be generalised and is not accurate enough
• Differences in definitions of disease, variations of drugs or drug doses, study design

Question 2

What are the aims and procedures of a meta-analysis? (8)

Answer 2

1) Combine the results of independent trials
2) Calculate the average ‘pooled’ effect
3) Evaluate overall strength and direction
4) Provide unbiased conclusion

The aims:
More statistical power due to larger combined sample size, so more reliable and less biased
Takes into account standard error and weights with effectiveness.

Question 3

What are the types of heterogeneity in a meta-analysis? (4)

Answer 3

Methodical heterogeneity
- differences in the way studies are conducted

Clinical heterogeneity
- differences in participant characteristics and patient population

Question 4

What are some biases in meta analyses? (6)

Answer 4

• Publication bias
• Selective outcome reporting bias
• Language bias
• Low income and high income countries
• Single/ multi centre trials
• Industry sponsorship

Question 5

What is publication bias and how can it be avoided? (5)

Answer 5

Not all studies conducted are published. A study is more likely to be published if the result is positive or if it is a large study

To avoid it:
Researchers should be aware of it, and encourage publication of all trials
Search unpublished trials in a trial registry