and meta-analyses

In document Field Trials of Health Interventions: A Toolbox (Page 67-72)

Systematic reviews involve managing large quantities of information. There are vari- ous software packages available which can be used to prepare systematic reviews. For example, the Cochrane Collaboration produces a freely available program called RevMan which is a Windows-based software package designed to enter reviews in the Cochrane format. This includes an analysis module (MetaView) for quantitative summaries.

Results of searches from electronic databases can also be automatically down- loaded into a reference manager software package, such as EndNote, and, from there, exported into database packages, such as Excel, for review and assessment of abstracts. Standard statistical packages, such as Stata, include modules for meta-analyses.

4 Reporting findings from systematic reviews

There are several guidelines for reporting results of a systematic review. The most re- cent 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 implica- tions 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 de- sirable and undesirable effects, and whether the intervention represents a wise use of resources.

33 4: REPORTING fINDINGS fROM SYSTEMATIC REVIEWS

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

34 CHAPTER 3: REVIEWING THE LITERATURE

Section/topic # Checklist item Reported on page #

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

35 4: REPORTING fINDINGS fROM SYSTEMATIC REVIEWS

Section/topic # Checklist item Reported on page #

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 l evel 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)

Table 3.4 (continued) PRISMA guidelines for systematic reviews and meta-analyses

36 CHAPTER 3: REVIEWING THE LITERATURE

References

Clark, S. and Horton, R. 2010. Putting research into context—revisited. Lancet, 376, 10–11. Egger, M., Smith, G. D., and Altman, D. G. 2001. Systematic reviews in health care: meta-analysis

in context. London: BMJ Books.

Glasziou, P. 2001. Systematic reviews in health care: a practical guide. Cambridge, New York: Cambridge University Press.

Guyatt, G. H., Oxman, A. D., Vist, G. E., et al. 2008. GRADE: an emerging consensus on rating quality of evidence and strength of recommendations. BMJ, 336, 924–6.

Higgins, J. and Green, S. P. 2008. Cochrane handbook for systematic reviews of interventions [Online]. Oxford: Wiley-Blackwell. Available at: <http://tectutorials.com/Resources/ AHRQ%20Modules/UoCTrainingMaterials/CochraneHB/booktext.pdf>.

Higgins, J. P., Thompson, S. G., Deeks, J. J., and Altman, D. G. 2003. Measuring inconsistency in meta-analyses. BMJ, 327, 557–60.

Jenkins, M. 2004. Evaluation of methodological search filters—a review. Health Information & Libraries Journal, 21, 148–63.

Khan, K. S. 2003. Systematic reviews to support evidence-based medicine: how to review and apply findings of healthcare research. London: Royal Society of Medicine Press.

Liberati, A., Altman, D. G., Tetzlaff, J., et al. 2009. The PRISMA statement for reporting sys- tematic reviews and meta-analyses of studies that evaluate health care interventions: expla- nation and elaboration. PLoS Medicine, 6, e1000100.

Moher, D., Liberati, A., Tetzlaff, J., Altman, D. G., and Group, P. 2009. Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement. PLoS Medicine, 6, e1000097.

Napierala Mavedzenge, S. M., Doyle, A. M., and Ross, D. A. 2011. HIV prevention in young people in sub-Saharan Africa: a systematic review. Journal of Adolescent Health, 49, 568–86. Zhang, L. N., Yang, Y. M., Xu, Z. R., Gui, Q. F., and Hu, Q. Q. 2010. Chewing substances with

or without tobacco and risk of cardiovascular disease in Asia: a meta-analysis. Journal of Zhejiang University SCIENCE B, 11, 681–9.

Section/topic # Checklist item Reported on page #

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 state- ment, PLoS Medicine, Volume 6, Issue 7, e1000097, Copyright © Moher et al. 2009. This table is repro- duced 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 origi- nal author and source are credited.

Chapter 4

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