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Results of meta-analysis
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Risk of bias of the individual studies are presented. low RoB “++” (study is comparable to a randomized study); moderate RoB “ + ” (study correctly performed represents a non-randomized study); significant RoB “−” (study has some serious problems); critical RoB “−−” (study has too many serious problems); unclear RoB “?” (due to lack of information no assessment is possible)
