Is the evidence appropriate for my setting? How do I know I can trust the evidence?
It’s not an exact science, but critically appraising your evidence will help you decide whether it’s appropriate for your setting and of sufficient quality to be used for effective decison making.
Having found the evidence relevant to your project (see Step 2, Accessing Evidence), you now need to establish whether it’s trustworthy and relevant, which means:
- Establishing a full understanding of the message being put forward.
- Evaluating the author’s perspective.
- Evaluating the evidence supporting that message.
This is important in commissioning where a range of evidence is often used to build a picture. Critical appraisal involves using judgement to reach concensus – it is not clear cut and there is no right answer.
The importance of critical appraisal
Remember: accepting the evidence on face value without questioning it can be dangerous.
Example: newspaper headlines following the result of dementia research, 09/09/2010:
- Vitamin B is revolutionary new weapon against Alzheimer’s Disease (Daily Telegraph).
- Daily vitamin pill could reduce dementia’s effects by up to 50 per cent (The Independent).
These stories relied on specific research, looking at the rate of change in brain measurements in patients taking B vitamins over two years. The rate of change (in the type of individual in the study sample) is all that can be said about it. It was not conducted in patients with dementia or Alzheimers.
That’s why critical reading and thinking is so important when appraising evidence. There is support available for this in your area – see Contacts page for your local details.
Conducting critical appraisal
Unless you are very confident of your critical appraisal skills (and have the time required to do it), we suggest you ask for specialist help or have some training (see below).
Critical appraisal tools
There are a number of tools available to help you to appraise research such as the CASP tool. Or read this brief guide locally adapted from a University of Oxford, Centre of Evidence-Based Medicine training handbook.
Critical appraisal training
If you have the time, and wish to develop skills in critical thinking and reading, please contact these organisations that offer training:
- Primary Care Library Service
- Your local Public Health team
- CLAHRC West
- School of Social and Community Medicine at Bristol University short courses.
You may also wish to read the following:
Or take these online tutorials:
- Online tutorial on critical appraisal (Healthcare Improvements, Scotland).
- Finding and appraising the evidence (Health Knowledge).
Useful tip… Look behind the headlines
NHS Choices provide a useful online service called Behind the Headlines. It examines the health-related news appearing in the morning press and produces an un-biased analysis of the original research (and how accurately it was reported) by the end of the day.
Once you’ve found relevant evidence and had it appraised, you will need to think about how to apply it to your context, the next step in the cycle.