Table 1 AMSTAR - A MeaSurement Tool to Assess Reviews (from [22])

2. Was there duplicate study selection and data extraction?

There should be at least two independent data extractors, and a consensus procedure for disagreements should be in place

□ Yes

□ No

□ Can't answer

□ Not applicable

3. Was a comprehensive literature search performed?

At least two electronic sources should be searched. The report must include the years and databases used (e.g. Central, EMBASE, and MEDLINE). Key words and/or MESH terms must be stated and, where feasible, the search strategy should be provided. All searches should be supplemented by consulting current contents, reviews, textbooks, specialised registers, or experts in the particular field of study, and by reviewing the references in the studies found

□ Yes

□ No

□ Can't answer

□ Not applicable

4. Was the status of publication (i.e. grey literature) used as an inclusion criterion?

The authors should state that they searched for reports regardless of their publication type. The authors should state whether or not they excluded any reports (from the systematic review), based on their publication status, language, etc.

□ Yes

□ No

□ Can't answer

□ Not applicable

5. Was a list of studies (included and excluded) provided?

A list of included and excluded studies should be provided

□ Yes

□ No

□ Can't answer

□ Not applicable

6. Were the characteristics of the included studies provided?

In an aggregated form such as a table, data from the original studies should be provided about the participants, interventions and outcomes. The ranges of characteristics in all the studies analysed e.g. age, race, sex, relevant socioeconomic data, disease status, duration, severity, or other diseases should be reported

□ Yes

□ No

□ Can't answer

□ Not applicable

7. Was the scientific quality of the included studies assessed and documented?

'A priori' methods of assessment should be provided (e.g. for effectiveness studies if the author(s) chose to include only randomised, double-blind, placebo controlled studies, or allocation concealment as inclusion criteria). For other types of studies, alternative items will be relevant

□ Yes

□ No

□ Can't answer

□ Not applicable

8. Was the scientific quality of the included studies used appropriately in formulating conclusions?

The methodological rigour and scientific quality of the studies should be considered in the analysis and the conclusions of the review, and explicitly stated when formulating recommendations

□ Yes

□ No

□ Can't answer

□ Not applicable

9. Were the methods used to combine the findings of studies appropriate?

For the pooled results, a test should be done to ensure the studies were combinable and to assess their homogeneity (i.e. Chi-squared test for homogeneity, I²). If heterogeneity exists a random effects model should be used and/or the clinical appropriateness of combining should also be taken into consideration (i.e. was it appropriate to combine the results?)

□ Yes

□ No

□ Can't answer

□ Not applicable

10. Was the likelihood of publication bias assessed?

An assessment of publication bias should include a combination of graphical aids (e.g. a funnel plot, other available tests) and/or statistical tests (e.g. Egger regression test)

□ Yes

□ No

□ Can't answer

□ Not applicable

11. Was the conflict of interest stated?

Potential sources of support should be clearly acknowledged in both the systematic review and the included studies

□ Yes

□ No

□ Can't answer

□ Not applicable