Systematic Reviews
Inclusion and exclusion criteria
Inclusion and exclusion criteria are a list of pre-defined characteristics to which literature must adhere to be included in a study. They are vital for the decision-making progress on what to review when undertaking a systematic review and will also help with systematic literature reviews.
You should be able to establish your inclusion/exclusion criteria during the process of defining your question. These criteria clearly demonstrate the scope of the study and provide justification for the exclusion of any information that does not meet these characteristics.
Example criteria
E.g. stage 4 lung disease patients
E.g. whether the study's reported outcomes are relevant to your study and have been presented objectively
E.g. randomised control trial
E.g. age, sex ethnicity etc.
E.g. last 5 years
E.g. over 100 participants
E.g. UK based
E.g. primary research, peer-reviewed
E.g. community-based care
E.g. English
Precision vs Sensitivity
You should aim to be as extensive as possible when conducting searches for systematic reviews. However, it may be necessary to strike a balance between the sensitivity and precision of your search.
- Sensitivity – the number of relevant results identified divided by the total number of relevant results in existence
- Precision - the number of relevant results identified divided by the total number of results identified.
Increasing the comprehensiveness of a search will reduce its precision and will retrieve more non-relevant results. However,
... at a conservatively-estimated reading rate of two abstracts per minute, the results of a database search can be ‘scanread’ at the rate of 120 per hour (or approximately 1000 over an 8-hour period), so the high yield and low precision associated with systematic review searching is not as daunting as it might at first appear in comparison with the total time to be invested in the review. (Cochrane Handbook for Systematic Reviews of Interventions, 2008, Section 6.4.4)