Copyright ©The Author(s) 2017. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Meta-Anal. Aug 26, 2017; 5(4): 80-84
Published online Aug 26, 2017. doi: 10.13105/wjma.v5.i4.80
Assessing the quality of studies in meta-analyses: Advantages and limitations of the Newcastle Ottawa Scale
Claudio Luchini, Brendon Stubbs, Marco Solmi, Nicola Veronese
Claudio Luchini, Department of Diagnostics and Public Health, University and Hospital Trust of Verona, 37134 Verona, Italy
Claudio Luchini, Surgical Pathology Unit, Santa Chiara Hospital, 38122 Trento, Italy
Brendon Stubbs, Physiotherapy Department, South London and Maudsley NHS Foundation Trust, Denmark Hill, London SE5 8AZ, United Kingdom
Brendon Stubbs, Health Service and Population Research Department, Institute of Psychiatry, Psychology and Neuroscience King's College London, De Crespigny Park, London Box SE5 8AF, United Kingdom
Brendon Stubbs, Faculty of Health, Social Care and Education, Anglia Ruskin University, Chelmsford CM1 1SQ, United Kingdom
Marco Solmi, Department of Neurosciences, University of Padova, 35122 Padova, Italy
Marco Solmi, Nicola Veronese, Institute for Clinical Research and Education in Medicine, IREM, 35122 Padova, Italy
Nicola Veronese, National Research Council, Neuroscience Institute, Aging Branch, 35131 Padova, Italy
Author contributions: Luchini C and Solmi M wrote the manuscript; Stubbs B and Veronese N critically evaluated the manuscript; all the authors approved the final form and the submission.
Conflict-of-interest statement: None to declare.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:
Correspondence to: Claudio Luchini, MD, Department of Diagnostics and Public Health, University and Hospital Trust of Verona, 37134 Verona, Italy.
Telephone: +39-45-8124842 Fax: +39-45-8027136
Received: January 13, 2017
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.

Keywords: Quality, Meta-analysis, Newcastle Ottawa Scale

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.