In order to identify studies to include in the review Machado et al (2015) carried out a database search of 8 different databases, and they identify the key-words used. Petticrew and Roberts (2006) point out that although electronic databases are often the starting point, they may not be the only source of evidence, especially in the social sciences. Machado (2015) also used citation tracking on included studies and relevant existing systematic reviews. They also looked at relevant websites and searched trial registries for unpublished studies. …show more content…
The authors used a funnel plot, (which is a statistical way to identify publication bias) and concluded that no meta-analysis presented serious publication bias according to the GRADE approach. Egger and Smith (1998) highlight that studies with significant results have a higher tendency to be published or cited, another danger of publication bias is the inclusion of studies only in the English language, however in Machado et al (2015) there were no restrictions on languages or publication dates in the search.
Petticrew (2001) suggests that good quality systematic reviews have a clear question, strive to locate all relevant publications, discuss which studies are to be included or excluded and give a description of this process, examine the methods and potential biases in individual studies, and form conclusions based on the studies which are most methodologically sound. Machado et al (2015) appear to have followed these steps within their