Evidence-based Medicine Toolkit

30 Evidence-based Medicine Toolkit• What intervention/s were given, how and in what setting?• How were outcomes assessed?A point to consider is that the narrower the inclusion criteria, theless generalizable are the results. However, if inclusion criteria aretoo broad heterogeneity (see below) becomes an issue.3 Are the studies consistent, both clinically andstatistically?You have to use your clinical knowledge to decide whether thegroups of patients, interventions, and outcome measures weresimilar enough to merit combining their results. If not, this clinicalheterogeneity would invalidate the review.Similarly, you would question the review’s validity if the trials’results contradicted each other. Unless this statistical heterogeneitycan be explained satisfactorily (such as by differences inpatients, dosage, or durations of treatment), this should lead youto be very cautious about believing any overall conclusion fromthe review.Are the results important?Because systematic reviews usually examine lots of different results,the first step is for you to consider which patient group, interventionand outcome matters most to you.The most useful way of interrogating the results of systematicreviews is to look at the figures, illustrated below.