Evidence Based Practice

Critical appraisal is the process of carefully and systematically examining research to judge its trustworthiness, its value, and its relevance in a particular context.

Information, calculators, checklists, and tools to help you critically appraise research articles are provided on this page.

Sources: Appraising the Evidence. CQ University. 2010. Chambers, R. Clinical Effectiveness Made Easy: First Thoughts on Clinical Governance.  Oxford.  Radcliff Medical Press. 1998. Image: Tkgd2007. GPL. Wikimedia Commons.

Dr Greenhalgh's clearly written papers -- full-text links below -- teach users how to critically appraise the medical literature.   Originally appearing in the BMJ, her articles were later produced as a book:  How to Read a Paper. 

When appraising research, keep the following three criteria in mind:

Quality 
"Trials that are randomised and double blind, to avoid selection and observer bias, and where we know what happened to most of the subjects in the trial.

Validity
Trials that mimic clinical practice, or could be used in clinical practice, and with outcomes that make sense. For instance, in chronic disorders we want long-term, not short-term trials. We are [also] ... interested in outcomes that are large, useful, and statistically very significant (p < 0.01, a 1 in 100 chance of being wrong).

Size
Trials (or collections of trials) that have large numbers of patients, to avoid being wrong because of the random play of chance. For instance, to be sure that a number needed to treat (NNT) of 2.5 is really between 2 and 3, we need results from about 500 patients. If that NNT is above 5, we need data from thousands of patients.

These are the criteria on which we should judge evidence. For it to be strong evidence, it has to fulfil the requirements of all three criteria."

Source:  Critical Appraisal. Bandolier.