Results of studies included in a review are organized in a hierarchy: studies are nested within (optional) subgroups, which are nested within outcomes, which are nested within comparisons (see Figure 4.8.a). A study can be included several times among the analyses.
RevMan automatically generates forest plots illustrating data, effect estimates and results of meta-analyses (where selected) from the data entered into the ‘Data and analyses’ structure. The author is able to control whether, and how, meta-analyses are performed.
Note: The ‘Data and analyses’ should be considered as supplementary information because they may not appear in some formats of the published review. Key forest plots (containing data for each study) may be selected to be always included with the full text of the review by selecting them as figures (see Section 4.9). The full published Cochrane review in the CDSR will, however, contain all of the ‘Data and analyses’ section as a series of forest plots or tables.
Authors should avoid listing comparisons or outcomes for which there are no data (i.e. have forest plots with no studies). Instead, authors should note in the text of the review that no data are available for the comparisons. However, if the review has a ‘Summary of findings’ table, the main outcomes should be included in this irrespective of whether data are available from the included studies.
See also
Analyses are addressed in Chapter 9: including discussion of comparisons (Section 9.1.6), types of outcome data (Section 9.2) and subgroups (Section 9.6). Useful conversions from reported data to the required format are provided in Chapter 7 (Section 7.7).
Comparison
The comparisons should correspond to the questions or hypotheses under ‘Objectives’.
Outcome
Five types of outcome data are possible: dichotomous data, continuous data, ‘O – E’ and ‘V’ statistics, generic inverse variance (estimate and standard error) and other data (text only).
Subgroup
Subgroups may relate to subsets of studies (for example, trials using different durations of physiotherapy) or to a subdivision of the outcome (for example, short-term, medium-term, long-term).
Study data
Data for each study must be entered in a particular format specific to the type of outcome data (e.g. a sample size, mean and standard deviation for each group for continuous data).