What is critical appraisal?
Critical appraisal is:
...the assessment of evidence by systematically reviewing its relevance, validity and results to specific situations.
Chambers, R. (1998). Clinical effectiveness made easy: first thoughts on clinical governance. Oxford, Radcliffe Medical Press.
When you search Medline, the references that you retrieve have been published in recognised medical journals, some of which will have been peer reviewed. The peer review process means that the articles have been assessed by an expert in the field. This should help to prevent poor or inaccurate research being published. However, this does not mean that the research is always accurate or valid. Not all research is good research.
One of the key messages of evidence based medicine is: "Don't believe everything you read."
In 2006, the journal Science was forced to retract two of its published articles after the research was found to be fabricated. This means that you need to evaluate or critically appraise the quality of the research that you find.
The evidence based resources you will look at in this tutorial have been critically appraised.
Why is it important?
Critical appraisal is important because it:
- ensures a comprehensive assessment of the whole paper
- allows you to identify the strengths and weaknesses of a piece of research
- develops an improved understanding of the research methodology used to conduct the research
- allows you to relate the published research to your local situation
- enables you to identify any bias in the research
- facilitates the implementation of effective interventions in your clinical practice
How do you critically appraise an article?
The process of critical appraisal can be very time consuming. It requires you to carefully read the whole article, especially the research methodology and statistical analysis - not just the "easy" bits like the introduction, results and conclusion sections!
When reading an article you need to consider the following:
- Who has written the article? Are they a recognised author. Are they affiliated to a recognised institution?
- Why? What are the aims and objectives?
- How? Has the right research methodology been used?
- When? Is it recent or seminal research?
- Where? Has it been published in a recognised journal? Is it a peer reviewed journal?
- Do the results seem valid?
- Does the statistical evidence seem valid?
- Is there any obvious bias or conflict of interests?
- Do the conclusions stack up?
If you are unfamiliar with the process of critical appraisal, a good place to start is the Behind the Headlines service provided by NHS Choices.
Behind the Headlines reviews health related stories that have been reported in the media. It assesses:
- Where the information has come from
- Whether the information is valid
- Whether the results have accurately interpreted and reported
Activity: Look at the most recent entry in Behind the Headlines.
- Where has the information come from?
- What kind of study was it?
- What were the results?
- Have the results been interpreted accurately?
- What are the conclusions?
To undertake a more in depth critical appraisal of a particular research article there are a number of critical appraisal guides that you can use to help you evaluate the research you have found. The Critical Appraisal Skills Programme (CASP) provides appraisal tools or checklists covering specific research study designs and methodologies.
Activity: From the Appraisal Tools section of the CASP website, print off the Randomised Controlled Trials checklist. Use Section A to do a quick appraisal of the following article:
Murphy HR. Rayman G. Duffield K. Lewis KS. Kelly S. Johal B. Fowler D. Temple RC. (2007) Changes in the glycemic profiles of women with type 1 and type 2 diabetes during pregnancy. Diabetes Care. 30(11):2785-91.