Systematic Reviews

Deciding on review question

Start with clear question to be answered or hypothesis to be tested

May also start with clear question to be answered, but they more often involve general discussion of subject with no stated hypothesis

Searching for relevant studies

Strive to locate all relevant published and unpublished studies to limit impact of publication and other biases

Do not usually attempt to locate all relevant literature

Deciding which studies to include and exclude

Involve explicit description of what types of studies are to be included to limit selection bias on behalf of reviewer

Usually do not describe why certain studies are included and others excluded

Assessing study quality

Examine in systematic manner methods used in primary studies, and investigate potential biases in those studies and sources of heterogeneity between study results

Often do not consider differences in study methods or study quality

Synthesizing study results

Base their conclusions on those studies which are most methodologically sound

Often do not differentiate between methodologically sound and unsound studies