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critical appraisal

Critical Appraisal of a research article
Dr Vimal Karani
Associate Professor in Nutrigenetics & Nutrigenomics
Programme Director for UG Nutrition Degree programmes
University of Reading, UK
What is a critical appraisal?
 Critical appraisal is a systematic process used to identify the strengths and
weaknesses of a research article in order to assess the usefulness and validity of
research findings.
 Critical appraisal is an important element of evidence- based medicine
What are the components of a critical appraisal?
Two important components:
1. An evaluation of the appropriateness of the study design for the research question &
2. A careful assessment of the key methodological features of this design.
Other factors to consider
the suitability of the statistical methodologies used and their subsequent
the relevance of the research to one's own practice.
Things to remember
 Decide whether studies have been undertaken in a way that makes their findings
 Make sense of the results
 Know what these results mean in the context of the decision they are making
Different types of questions require different study designs
 Aetiology: what caused this illness?
 Diagnosis: what does this test result mean in this patient?
 Prognosis: what is likely to happen to this patient?
 Harm: is having been exposed to this substance likely to do harm, and, if so, what?
 Effectiveness: is this treatment likely to help patients with this illness?
 Qualitative: what are the outcomes that are most important to patients with this
Things to remember
When reading any research (systematic review, RCT, economic evaluation or other study
design), it is important to remember that there are three broad things to consider:
 Validity,
 Results,
 Relevance
It is always necessary to consider the following questions:
 Has the research been conducted in such a way as to minimise bias?
 If so, what does the study show?
 What do the results mean for the particular patient or context in which a
decision is being made?
You will be provided with a research article
You will have to identify the strengths and weaknesses of the article
General epidemiology - principles
disease or continuous trait
continuous or categorical
observational (cohort, case-control),
experimental (trials)
Co-variables/confounders: e.g. age, gender, …
Epidemiological studies
Prospective Cohort
Randomised Trial
Cohort studies – study population
Selection of study population important to
avoid bias
Select on exposure vs non-exposure
Select defined population
Age-range suitable for follow-up
often difficult to find representative sample due
to selection bias
onset of disease within 10 – 15 years
Large sample size for rare diseases