1. STROBE Statement revision
Reporting Guideline for Systematic Reviews and Meta-Analyses: the PRISMA Statement
Doug Altman
STROBE Statement revision

2. QUOROM Statement Developed in 1996 Published in 1999
Following CONSORT model
Published in 1999
Checklist and flow diagram
Since 1996 increased evidence base from methodological and empirical research
e.g. Cochrane Methodology Register
1000 entries in 1999
8255 entries in 2006
Important deficiencies in QUOROM were recognised

3. Update/revision of QUOROM
A 3-day meeting was held in Ottawa, Canada, in June 2005
29 participants: systematic reviewers, methodologists, editors and a consumer
Name changed to PRISMA
Draft checklist - much iteration subsequently
Revised Statement published in 2009 in 5 journals
27-item checklist
four-phase flow diagram
Identification, screening, eligibility, inclusion
Moher D, Liberati A, Tetzlaff J, Altman DG, the PRISMA Group. Preferred reporting items for systematic reviews and meta-analyses: the PRISMA Statement. 2009
PLoS Med; Open Med; Ann Intern Med; BMJ; J Clin Epidemiol

4. Conceptual issues affecting the update
Distinction between articles and studies
Iterative nature of completing a systematic review
Need to distinguish between conduct and reporting of primary studies
Quality assessment
Key idea is “risk of bias”
Both study level and outcome level assessment
Need to consider risk of reporting bias (between and within study)
“Systematic review” or “meta-analysis”?

5. Rationale for checklist items
Necessary to evaluate the study
Evidence-based, whenever possible
Minimum set of essential items

7. Flow diagram Original QUOROM Statement:
“Provide a meta-analysis profile summarising trial flow”
Revised Statement is more precise:
“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”

8. STROBE Statement revision
24 August 2010
STROBE Statement revision

9. PRISMA – Item 8, search
“Present full electronic search strategy for at least one database, including any limits used, such that it could be repeated”
Rationale for reporting search
Allows interested readers to assess the comprehensiveness and completeness of the search, and to replicate it
Essential for updating (i.e., keeping systematic reviews up-to-date)
Look at Moher 2007 for estimate of number of reviews that report full electronic search.

10. PRISMA – Item 12, Risk of bias in individual studies
“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.”
Rationale for reporting risk of bias
The likelihood that the treatment effect reported in a systematic review approximates the truth depends on the validity of the included studies, as certain methodological characteristics may be associated with effect sizes
For example, trials without reported adequate allocation concealment exaggerate treatment effects on average compared to those with adequate concealment.
Therefore, it is important for authors to describe any methods that they used to gauge the risk of bias in the included studies and how that information was used.
Additionally, authors should provide a rationale if no assessment of risk of bias was undertaken.

11. Reporting risk of bias
Authors should report how they assessed risk of bias
Whether assessment was in a blind manner
If assessments were completed by more than one person, and if so, whether they were completed independently.
Report any calibration exercises among review team members that were done.
Report how their assessments of risk of bias are used subsequently in the data synthesis

12. PRISMA – Item 17, study selection
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

13. Caughey et al. Ann Intern Med 2009
Fuccio et al. Ann Intern Med 2007

15. PRISMA Explanation and Elaboration (E&E)
Published in 4 journals –
BMJ, Ann Intern Med, PLoS Med, J Clin Epidemiol
STROBE Statement revision

16. Evidence of selective reporting of outcomes in RCTs
Comparison of 102 trial protocols with 122 subsequent publications
Nearly two-thirds had a change in at least one primary outcome between the protocol and publication
Statistically significant outcomes had a higher likelihood of being reported compared to non-significant ones
[Chan et al JAMA 2004]
Present data on risk of bias of each study and, if available, any outcome-level assessment (see Item 12).
Present results of any assessment of risk of bias across studies (see Item 15).

17. PRISMA is not specific
Most of the checklist is not specific to RCTs or to studies of interventions
Can be the basis for extension to other study designs
Box 2:
Finally, the type of study design(s) included in the review should be reported. Some reviews only include reports of randomized trials whereas others have broader design criteria and include randomized trials and certain types of observational studies. Still other reviews, such as those specifically answering questions related to harms, may include a wide variety of designs ranging from cohort studies to case reports. Whatever study designs are included in the review, these should be reported.

18. STROBE Statement revision
PRISMA E&E
“We developed the PRISMA Statement and this explanatory document to help authors report a wide array of systematic reviews to assess the benefits and harms of a health care intervention. We consider most of the checklist items relevant when reporting systematic reviews of nonrandomized studies assessing the benefits and harms of interventions.
However, we recognize that authors who address questions relating to etiology, diagnosis, or prognosis, for example, and who review epidemiological or diagnostic accuracy studies may need to modify or incorporate additional items for their systematic reviews.”
24 August 2010
STROBE Statement revision

19. STROBE Statement revision
PRISMA E&E
“We believe that the issues we have highlighted in this paper are relevant to ensure transparency and understanding of the processes adopted and the limitations of the information presented in systematic reviews of different types. We hope that PRISMA can be the basis for more detailed guidance on systematic reviews of other types of research, including diagnostic accuracy and epidemiological studies.”
24 August 2010
STROBE Statement revision

20. Ramakrishnan et al, Lancet Inf Dis 2010
24 August 2010
Ramakrishnan et al, Lancet Inf Dis 2010
STROBE Statement revision

21. STROBE Statement revision
24 August 2010
Lim et al PLoS One, 2010
STROBE Statement revision

22. STROBE Statement revision
24 August 2010
STROBE Statement revision