Methods
[fixed, level 1 heading]
The Methods section in a protocol should be written in the future tense. Because Cochrane reviews are updated as new evidence accumulates, methods outlined in the protocol should generally be written as if a suitably large number of studies will be identified to allow the objectives to be met (even if it is known this is not the case at the time of writing).
The Methods section in a review should be written in the past tense, and should describe what was done to obtain the results and conclusions of the current review. Review authors are encouraged to cite their protocol to make it clear that there was one. Often a review is unable to implement all of the methods outlined in the protocol, usually because there is insufficient evidence. In such circumstances, it is recommended that the methods that were not implemented be outlined in the section headed ‘Differences between protocol and review’ (see below), so that it serves as a protocol for future updates of the review.
Criteria for considering studies for this review
[fixed, level 2 heading]
Types of studies
[fixed, level 3 heading]
Eligible study designs should be stated here, along with any thresholds for inclusion based on the conduct of the studies or their risk of bias. For example, ‘All randomized controlled comparisons’ or ‘All randomized controlled trials with blind assessment of outcome’. Exclusion of particular types of randomized studies (for example, cross-over trials) should be justified.
See also
Types of participants
[fixed, level 3 heading]
The diseases or conditions of interest should be described here, including any restrictions such as diagnoses, age groups and settings. Subgroup analyses should not be listed here (see ‘Subgroup analysis and investigation of heterogeneity’ under ‘Methods’).
See also
Types of interventions
[fixed, level 3 heading]
Experimental and comparator interventions should be defined here, under separate subheadings if appropriate. It should be made clear which comparisons are of interest. Restrictions on dose, frequency, intensity or duration should be stated. Subgroup analyses should not be listed here (see ‘Subgroup analysis and investigation of heterogeneity’ under ‘Methods’).
See also
Types of outcome measures
[fixed, level 3 heading]
Note that outcome measures do not always form part of the criteria for including studies in a review. If they do not, then this should be made clear. Outcome measures of interest should be listed in this section whether or not they form part of the eligibility criteria.
See also
The importance of addressing patient-relevant outcomes is discussed further in Chapter 11 (Section 11.5.2); see also an extended discussion of patient-reported outcomes in Chapter 17.
Primary outcomes
[recommended, level 4 heading]
The review’s primary outcomes should normally reflect at least one potential benefit and at least one potential area of harm, and should be as few as possible. It is normally expected that the review should be able to analyse these outcomes if eligible studies are identified, and that the conclusions of the review will be based in large part on the effects of the interventions on these outcomes.
Secondary outcomes
[recommended, level 4 heading]
Non-primary outcomes should be listed here. The total number of outcomes addressed should be kept as small as possible.
The following optional (level 4) headings may be helpful, as supplements or replacements for the headings above:
Main outcomes for ‘Summary of findings’ table
Timing of outcome assessment
Adverse outcomes
Economic data
Search methods for identification of studies
[fixed, level 2 heading]
The methods used to identify studies should be summarized. The following headings are recommended. Before starting to develop this section, authors should contact their Cochrane Review Group (CRG) for guidance.
See also
Electronic searches
[recommended, level 3 heading]
The bibliographic databases searched, the dates and periods searched and any constraints such as language should be stated. The full search strategies for each database should be listed in an appendix to the review. If a CRG has developed a specialized register of studies and this is searched for the review, a standard description of this register can be referred to but information should be included on when and how the specialized register was most recently searched for the current version of the review and the search terms used should be listed.
See also
Searching other resources
[recommended, level 3 heading]
List grey literature sources, such as internal reports and conference proceedings. If journals are specifically handsearched for the review, this should be noted but handsearching done by the authors to help build the specialized register of the CRG should not be listed because this is covered in the standardized description of the register. List people (e.g. trialists or topic specialists) and organizations who were contacted. List any other sources used, which may include, for example, reference lists, the World Wide Web or personal collections of articles.
The following optional headings may be used, either in place of ‘Searching other resources’ (in which case they would be level 3 headings) or as subheadings (level 4).
Grey literature
Handsearching
Reference lists
Correspondence
See also
Data collection and analysis
[fixed, level 2 heading]
This should describe the methods for data collection and analysis.
Selection of studies
[recommended, level 3 heading]
The method used to apply the selection criteria. Whether they are applied independently by more than one author should be stated, along with how any disagreements are resolved.
See also
Data extraction and management
[recommended, level 3 heading]
The method used to extract or obtain data from published reports or from the original researchers (for example, using a data collection form). Whether data are extracted independently by more than one author should be stated, along with how any disagreements are resolved. If relevant, methods for processing data in preparation for analysis should be described.
See also
Data collection is discussed in Chapter 7, including which data to collect (Section 7.3), sources of data (Section 7.4), data collection forms (Section 7.5) and extracting data from reports (Section 7.6)
Assessment of risk of bias in included studies
[recommended, level 3 heading]
The method used to assess risk of bias (or methodological quality). Whether methods are applied independently by more than one author should be stated, along with how any disagreements are resolved. The tool(s) used should be described or referenced, with an indication of how the results are incorporated into the interpretation of the results.
See also
Measures of treatment effect
[recommended, level 3 heading]
The effect measures of choice should be stated. For example, odds ratio (OR), risk ratio (RR) or risk difference (RD) for dichotomous data; mean difference (MD) or standardized mean difference (SMD) for continuous data. The following optional headings may be used, either in place of ‘Measures of treatment effect’ (in which case they would be level 3 headings) or as subheadings (level 4):
Dichotomous data
Continuous data
Time-to-event data
See also
Unit of analysis issues
[recommended, level 3 heading]
Special issues in the analysis of studies with non-standard designs, such as cross-over trials and cluster-randomized trials, should be described. Alternatively, optional (level 3) headings specific to the types of studies may be used, such as:
Cluster-randomised trials
Cross-over trials
Studies with multiple treatment groups
See also
Unit of analysis issues are discussed in Chapter 9 (Section 9.3).
Some non-standard designs are discussed in detail in Chapter 16, including cluster-randomized trials (Section 16.3), cross-over trials (Section 16.4), and studies with multiple intervention groups (Section 16.5). Non-randomized studies are discussed in Chapter 13.
Dealing with missing data
[recommended, level 3 heading]
Strategies for dealing with missing data should be described. This will principally include missing participants due to drop-out (and whether an intention-to-treat analysis will be conducted), and missing statistics (such as standard deviations or correlation coefficients).
See also
Issues relevant to missing data are discussed in Chapter 16 (Sections 16.1) and intention-to-treat issues in Chapter 16 (Section 16.2).
Assessment of heterogeneity
[recommended, level 3 heading]
Approaches to addressing clinical heterogeneity should be described, along with how the authors will determine whether a meta-analysis is considered appropriate. Methods for identifying statistical heterogeneity should be stated (e.g. visually, using I2, using a chi-squared test).
See also
Assessment of reporting biases
[recommended, level 3 heading]
This section should describe how publication bias and other reporting biases are addressed (for example, funnel plots, statistical tests, imputation). Authors should remember that asymmetric funnel plots are not necessarily caused by publication bias (and that publication bias does not necessarily cause asymmetry in a funnel plot).
See also
Reporting biases are discussed in Chapter 10.
Data synthesis
[recommended, level 3 heading]
The choice of meta-analysis method should be stated, including whether a fixed-effect or a random-effects model is used. If meta-analyses are not undertaken, systematic approaches to synthesizing the findings of multiple studies should be described.
See also
Subgroup analysis and investigation of heterogeneity
[recommended, level 3 heading]
All planned subgroup analyses should be listed (or independent variables for meta-regression). Any other methods for investigating heterogeneity of effects should be described.
See also
Sensitivity analysis
[recommended, level 3 heading]
This should describe analyses aimed at determining whether conclusions are robust to decisions made during the review process, such as inclusion/exclusion of particular studies from a meta-analysis, imputing missing data or choice of a method for analysis.
See also
Summary of findings table
[recommended, level 3 heading]
This section should describe the methods used to prepare any ‘Summary of findings’ tables. It should include information about (i) which populations (including the specification of low, medium or high risk populations), interventions and comparisons are being addressed by one or more ‘Summary of findings’ tables, and why; (ii) the source of any external information used in the ‘Assumed risk’ column; (iii) a brief comment that the GRADE approach to assessing the quality of the body of evidence is being used; and (iv) any departures from the standard methods described in Chapter 11 and Chapter 12, along with a justification for such departures. The review’s main outcomes, i.e. those intended for inclusion in the ‘Summary of findings’ table, should have been listed under the section ‘Types of outcome measures’.
See also
‘Summary of findings’ tables are discussed in Chapter 11 (Section 11.5) and the GRADE system is described in Chapter 12 (Section 12.2) and the help file in the GRADEpro software.
Note: this heading is not included by default within the RevMan software, but may be added by the review author.
The following further, optional (level 3) headings for the Methods section may be helpful:
Economics issues
Methods for future updates
Authors seeking to cover economics aspects of interventions in a review will need to consider economics issues from the earliest stages of developing a protocol.
See also
Economics issues are discussed in Chapter 15.
Issues in updating reviews are discussed in Chapter 3.