Systematic reviews

Preliminary considerations

The aim of this type of research is to produce a clinical recommendation as a response to a focused and advanced clinical question, through the construction of a reproducible search algorithm in order to find, screen and critically assess all the bibliography dealing with the selected topic.

The most widely used editorial support system for writing this type of document is PRISMA, which has been used as the basis for these Guidelines.

Rules for the abstract and paper
The paper to be presented should comprise the following sections:

1) Title: include the term systematic review, meta-analysis, or both.

2) Introduction: contextualize the topic, pointing out the need to carry out the study, state the objectives with a research question constructed according to the PICO strategy (or other variants, e.g., PICOT, PICOD…).

3) Methods:
• Indicate whether a prior registration of the protocol for the systematic review has been carried out and, if so, where and how it can be accessed (e.g., PROSPERO).
• Define the study criteria, their characteristics (type of experimental design), considering the initial question (e.g., PICO, follow-up, etc.).
• Information sources: describe all information sources considered in the search, such as databases, grey literature, manual searches, authors, languages, and explain the main search algorithm so that it may be reproduced.
• Literature selection: describe the selection process of the studies (e.g., screening, eligibility and, if applicable, the process of inclusion in the meta-analysis).
• Data collection process: describe the method of data collection (e.g., data collection by two independent researchers? in case of disagreement, was a third researcher the tie-breaker?)
• List of data: list and define all the variables by which the information was searched (e.g., PICOS, funding sources) and any hypotheses and simplifications made.
• Risks of bias for each paper: describe the methods for assessing the risks of bias for each paper and how this information was used in the data synthesis.
• Summary of measures: list the risk analysis measures.
• Summary of results: describe the methods of data treatment and combine the results of the studies, including measures of consistency (e.g., I2) for each meta-analysis, if performed.
• Risks of study bias: specify any risks-of-bias assessment that may affect the cumulative evidence (e.g., publication bias, selective reporting of studies).
• Additional analyses: describe the additional methods of analysis (e.g., sensitivity testing or subgroup analysis, meta-regression), if performed.
• Study selection: indicate the number of studies screened, assessed for eligibility and included in the review, with reasons for exclusion at each stage and ideally including a diagram.
• Study characteristics: for each study present the characteristics by which the data were extracted (e.g., sample size, PICOS, follow-up period) and provide citations.

4) Results:
• Results of individual studies: each study should present (advantages or disadvantages): (a) simple summary data for each intervention group; (b) effect and confidence intervals, preferably through a forest plot.
• Summary of results: the results of each meta-analysis performed must be provided, including confidence intervals and consistency measures.
• Risks of bias throughout the study: the results must include any risk-of-bias assessment between studies.
• Additional analysis: the results of additional analyses, if performed (e.g., sensitivity or subgroup analyses, meta-regression) must be provided.

5) Discussion:
• Summary of evidence: a summary of the main findings should be provided, including the strength of the evidence for each main outcome; relevance to key groups (e.g., health professionals, users and policy makers) should be considered.
• Limitations of the study: The limitations of the study and results obtained (e.g., risks of bias) should be discussed, as well as the limitations to be reviewed (e.g., incomplete retrieval of the identified research, reporting bias).

6) Conclusions:
• The conclusions must provide a general interpretation of the results in the context of other evidence and the implications for future research.

7) Sources of funding:
• The sources of funding for the systematic review or other sources (e.g., data supply) should be described, including the explicit role played by funders in the systematic review.

8) Conflict of interest disclosure statement (if any).