Module 3.2 Common themes in critical appraisal

Although different aspects of critical appraisal may apply more or less to different study types, several common themes underlay the process.

Validity, applicability, and clinical importance should be addressed during critical appraisal.

Click on each of the circles to find out more.

Validity 

The extent to which study results are likely to be true and free from bias and accurately represent the group studied.

Internal validity: does the study design minimise the risk of confounding or bias?

External validity: can the study results be applied to other settings, patient populations or time periods outside the study?

Applicability 

How results from a clinical trial or meta-analysis apply to a specific individual or clinical setting – applicability considers whether the research findings fit your local context.

Patients’ individual characteristics may affect how results from literature may apply to them. Factors which may affect a trial’s applicability to patients include social status, economic circumstances, their geographic location, sex, gender, ethnicity, disability, or sexual orientation. (1)

1 World Health Organisation [Internet]. Geneva, Switzerland: WHO; c2026. Health equity; [last updated 2021 Jul 7; cited 2026 Feb 4]. Available from https://www.who.int/health-topics/health-equity

Clinical Importance 

Results that are statistically significant may or may not be clinically significant.

A small benefit may be important in a serious condition but may not justify an intervention in a good prognosis disease.

Potential benefits must not be outweighed by harms and toxicities.

The benefits are clinically meaningful in duration and sustainable in the longer term.

The intervention is realistic, affordable and accessible in your clinical setting.