Were individual patient data used in the analysis?
This is a finer point to consider when assessing validity of a systematic review. We'd feel more assured if this was done, especially with regard to reports of subgroups.
If the review fails any of the above criteria, we need to decide if the flaw is significant and threatens the validity of the study. If this is the case, we'll need to look for another study to answer our question, Returning to our clinical scenario, the review we found satisfies all of the above criteria and we will proceed to assessing it for importance.
- Is this a systematic review of randomised trials?
- Does it include a methods section that describes: a) finding and including all the relevant trials, and b) assessing their individual validity?
Were the results consistent from study to study?
A finer point:
- Were individual patient data (or aggregate data) used in the analysis?