Study design: should blinded and unblinded outcome assessment be included, or should study inclusion be restricted by other aspects of methodological criteria? Should abstracts whose results cannot be confirmed in subsequent publications be included in the review?Ĭharacteristics of participants: where a majority but not all people in a study meet an age range, should the study be included?Ĭharacteristics of the intervention: what range of doses should be included in the meta-analysis?Ĭharacteristics of the comparator: what criteria are required to define usual care to be used as a comparator group?Ĭharacteristics of the outcome: what time-point or range of time-points are eligible for inclusion? There are many decision nodes within the systematic review process which can generate a need for a sensitivity analysis. A sensitivity analysis asks the question, “Are the findings robust to the decisions made in the process of obtaining them?”. For example, if the eligibility of some studies in the meta-analysis is dubious because they do not contain full details, sensitivity analysis may involve undertaking the meta-analysis twice: first, including all studies and second, only including those that are definitely known to be eligible. A sensitivity analysis is a repeat of the primary analysis or meta-analysis, substituting alternative decisions or ranges of values for decisions that were arbitrary or unclear. It is desirable to prove that the findings from a systematic review are not dependent on such arbitrary or unclear decisions. Further decisions are unclear because there is no consensus on the best statistical method to use for a particular problem. Some decisions are unclear because the included studies themselves never obtained the information required: for example, the outcomes of those who unfortunately were lost to follow-up. Other decisions may be unclear because a study report fails to include the required information. For instance, if inclusion criteria involve a numerical value, the choice of value is usually arbitrary: for example, defining groups of older people may reasonably have lower limits of 60, 65, 70 or 75 years, or any value in between. Whilst many of these decisions are clearly objective and non-contentious, some will be somewhat arbitrary or unclear. The process of undertaking a systematic review involves a sequence of decisions. For the current version, please go to /handbook/current or search for this chapter here. This is an archived version of the Handbook.
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