WHY APPRAISE THE EVIDENCE?
Where an article is published, or who wrote it should not be an indication of its trustworthiness and relevance. Using critical appraisal skills and tools enables users of research evidence to reach their own judgements.
CASP approaches research in 3 steps:
1. Is the study valid?
The first step is to decide whether the study was unbiased by evaluating its methodological quality. Different criteria for validity of articles are used for different types of questions on: treatment, diagnosis, prognosis and economic evaluation. Depending on the validity of an article we can classify it within a scale of levels of evidence and degrees of recommendation.
2. What are the results?
If we decide that the study is valid, we can go on to look at the results. At this step we consider whether the study’s results are clinically important. For example, did the experimental group show a significantly better outcome compared with the control group? We also consider how much uncertainty there is about the results, as expressed in the form of p values, confidence intervals and sensitivity analysis.
3. Are the results useful?
Once you have decided that your evidence is valid and important, you need to think about how it applies to your question. It is likely, for example, that your patient or population may have different characteristics to those in the study. Critical appraisal skills provides a framework within which to consider these issues in an explicit, transparent way.
Take a look at CASP's freely available checklists for helping to appraise research papers here