Table 1 Result of critical self-assessment of systematic review quality (AMSTAR)

(1) Was an 'a priori' design provided? The research question and inclusion criteria should be established before the conduct of the review.

X

X

X

X

X

X

X

(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.

X

X

X

X

X

X

X

(3) Was a comprehensive literature search performed? At least two electronic sources should be searched. The report must include 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, textbooks, specialized registers, or experts in the particular field of study, and by reviewing the references in the studies found.

X

X

X

X

X

X

X

(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.

X

X

X

X

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

X

X

X

X

X

X

X

(6) Were the characteristics of the included studies provided? In an aggregated form such as table, data from the original studies should be provided on the participants, interventions and outcomes. The ranges of characteristics in all studies analysed e.g. age, race, sex, relevant socio-economic data, disease status, severity, or other diseases should be reported.

X

X

X

X

X

X

X

(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); or other types of studies alternative items will be relevant.

X

X

X

X

X

X

X

(8) Was the scientific quality of the included studies used appropriately in formulating conclusions? The result of the methodological rigor and scientific quality should be considered in the analysis and the conclusions of the review and explicitly stated in formulating recommendations.

X

X

X

X

X

(9) Were the methods used to combine the findings of the studies appropriate? For the pooled results, a test should be done to ensure the studies were combinable, 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 be taken into consideration (i.e. is it sensible to combine?).

X

X

X

X

X

X

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

X

(11) Was the conflict of interest stated? Potential source of support should be clearly acknowledged in both the systematic review and the included studies.