We've done our literature search and found some evidence. It's time to decide if it's valid and important before we can apply the evidence to our patients. The three things to bear in mind are quality, validity, and size (Bandolier):
- Quality: trials that are randomized 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 not interested in small but marginally statistically significant (p < 0.05, say, or a 1 in 20 chance of being wrong), but 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.
We recommend you to use the links below to find helpful videos and checklists for appraising articles.
