3.4: Reporting findings from systematic reviews

There are several guidelines for reporting results of a systematic review. The most recent are the PRISMA guidelines (<http://www.prisma-statement.org>) which are given in Table 3.4 (Moher et al., 2009). These include a full description of the rationale for the review, the research question, methods used, and analyses. Reviewers will then need to summarize their main findings, including the strengths and limitations of the review, the strength of the evidence for each main outcome, and the relevance to different population groups.

Finally, the results of the systematic review need to be assessed for their implications for policy and future research. One system to assist with interpreting results of systematic reviews is the GRADE system (Grading of Recommendations Assessment, Development, and Evaluation) (Guyatt et al., 2008). This gives guidelines as to whether results from a systematic review provide ‘strong’ or ‘weak’ evidence. This includes not only results of a systematic review, but also an evaluation of the balance between desirable and undesirable effects, and whether the intervention represents a wise use of resources.

Table 3.4 PRISMA guidelines for systematic reviews and meta-analyses

Section/topic	#	Checklist item	Reported on page #
TITLE
Title	1	Identify the report as a systematic review, meta-analysis, or both
ABSTRACT
Structured summary	2	Provide a structured summary, including, as applicable: background; objectives; data sources; study eligibility criteria, participants, and interventions; study appraisal and synthesis methods; results; limitations; conclusions and implications of key findings; systematic review registration number
INTRODUCTION
Rationale	3	Describe the rationale for the review in the context of what is already known
Objectives	4	Provide an explicit statement of questions being addressed with reference to participants, interventions, comparisons, outcomes, and study design (PICOS)
METHODS
Protocol and registration	5	Indicate if a review protocol exists, if and where it can be accessed (for example, Web address), and, if available, provide registration information, including registration number
Eligibility criteria	6	Specify study characteristics (for example, PICOS, length of follow-up) and report characteristics (for example, years considered, language, publication status) used as criteria for eligibility, giving rationale
Information sources	7	Describe all information sources (for example, databases with dates of coverage, contact with study authors to identify additional studies) in the search and date last searched
Search	8	Present full electronic search strategy for at least one database, including any limits used, such that it could be repeated
Study selection	9	State the process for selecting studies (i.e. screening, eligibility, included in systematic review, and, if applicable, included in the meta-analysis)
Data collection process	10	Describe method of data extraction from reports (for example, piloted forms, independently, in duplicate) and any processes for obtaining and confirming data from investigators
Data items	11	List and define all variables for which data were sought (for example, PICOS, funding sources) and any assumptions and simplifications made
Risk of bias in individual studies	12	Describe methods used for assessing risk of bias of individual studies (including specification of whether this was done at the study or outcome level) and how this information is to be used in any data synthesis
Summary measures	13	State the principal summary measures (for example, risk ratio, difference in means)
Synthesis of results	14	Describe the methods of handling data and combining results of studies, if done, including measures of consistency (for example, I2) for each meta-analysis
Risk of bias across studies	15	Specify any assessment of risk of bias that may affect the cumulative evidence (for example, publication bias, selective reporting within studies)
Additional analyses	16	Describe methods of additional analyses (for example, sensitivity or subgroup analyses, meta-regression), if done, indicating which were pre-specified
RESULTS
Study selection	17	Give numbers of studies screened, assessed for eligibility, and included in the review, with reasons for exclusions at each stage, ideally with a flow diagram
Study characteristics	18	For each study, present characteristics for which data were extracted (for example, study size, PICOS, follow-up period), and provide the citations
Risk of bias within studies	19	Present data on risk of bias of each study and, if available, any outcome level assessment (see item 12)
Results of individual studies	20	For all outcomes considered (benefits or harms), present, for each study: (a) simple summary data for each intervention group, (b) effect estimates and confidence intervals, ideally with a forest plot
Synthesis of results	21	Present results of each meta-analysis done, including confidence intervals and measures of consistency
Risk of bias across studies	22	Present results of any assessment of risk of bias across studies (see item 15)
Additional analysis	23	Give results of additional analyses, if done (for example, sensitivity or subgroup analyses, meta-regression) (see item 16)
DISCUSSION
Summary of evidence	24	Summarize the main findings, including the strength of evidence for each main outcome; consider their relevance to key groups (for example, health care providers, users, and policy makers)
Limitations	25	Discuss limitations at study and outcome level (for example, risk of bias) and at review level (for example, incomplete retrieval of identified research, reporting bias)
Conclusions	26	Provide a general interpretation of the results, in the context of other evidence, and implications for future research
FUNDING
Funding	27	Describe sources of funding for the systematic review and other support (for example, supply of data); role of funders for the systematic review

From Moher et al., Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement, PLoS Medicine, Volume 6, Issue 7, e1000097, Copyright © Moher et al. 2009. This table is reproduced from an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.