Published online Aug 26, 2017. doi: 10.13105/wjma.v5.i4.80
Peer-review started: January 16, 2017
First decision: February 17, 2017
Revised: May 18, 2017
Accepted: June 6, 2017
Article in press: June 8, 2017
Published online: August 26, 2017
One of the most important points in the meta-analyses is certainly represented by the assessment of the quality of the studies included in such research. The meta-analyses are considered the highest level of evidence in science. Also for this reason, the quality of the studies included should be accurately evaluated by standardized tools. The overall results of the meta-analysis depend indeed also on a rigorous evaluation of the studies quality. Among all the possible tools for this complex evaluation, the Newcastle Ottawa Scale (NOS) is one of the most used worldwide, above all for observational studies. In this review, we will discuss the strengths and limitation of the NOS, also on the basis of the branch of science in which it has been applied.
Core tip: To assess the quality of a meta-analysis is a remarkable point. In this review, we summarize the current evidence regarding the use of the Newcastle Ottawa Scale, one of the most used tool for evaluating quality in meta-analyses of observational studies. Taking also our works as example, we found that, even standardized and quick in its application, it suffers from some limitations, particularly when evaluating cross-sectional studies.