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GEM - critical appraisal educational module

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

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Critical Appraisal Module

This Educational Module discusses points to consider when undertaking a critical appraisal of a study. A systematic method of analysing for appraising a study is described.

1.What is the research question?

For most studies there should be a single sentence describing why the study was done and what hypothesis the authors were testing

2 . Consider first the type of study design used:

a) is it a cohort study (More information from GPnotebook)

b) is a case-control study (More information from GPnotebook)

c) is it blinded

d) if it is a crossover study what considerations are important (More information from GPnotebook ...Click here)

Additional information from GPN:

2. the study population investigated

a) what are the criteria for the study population to be included

- what age is the study population?

- what exclusion criteria are used?

- consider a major trial such as the PROACTIVE study

b) does the study population reflect the patient group who may receive the intervention in clinical practice

- the population chosen for a study may not be comparable to those encountered in everyday UK primary care

3. comparator drugs and doses studied

a) is there a comparator drug

b) if a comparator is used then what considerations are important (More information from GPnotebook...Click here)

4. sample size and power used in the study

a) what is the power of a statistical study

b) what is a typical value for the power of a study

c) why is the power of a study important when considering study endpoints

More information from GPnotebook...Click here

5.primary versus secondary endpoints and subgroup analysis

a) what is the difference between a primary and secondary endpoint

b) why should secondary endpoints and subgroup analysis be pre-speficied at the start of a study

More information from GPnotebook..Click here

6. duration of the study

a) some studies are terminated early because an intervention has demonstrated significant benefits over a comparator. What disadvantages might there be of doing this

More information from GPnotebook...Click here

7. study follow-up

a) it is important to consider the follow-up rate when evaluating a study

b) why would the power of a study be significant if there was a 20%+ drop-out rate from the study

8. is there a sponsorship or publication bias

9. other considerations

9.1) intention to treat analysis

a) what is intention to treat analysis

b) why is the method of analysis relevant to 'actual' clinical care

More information from GPnotebook...Click here

9.2) what p-values are used

More information from GPnotebook...Click here

9.3) what confidence intervals are used

More information from GPnotebook...Click here

9.4) comparing statistical and clinical significance of results

More information from GPnotebook...Click here

5. analysis of results e.g absolute risks, relative risks, odds ratios, numbers needed to treat, numbers needed to harm, Kaplan-Meier survival curves

More information:

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