Letters To The Editor
Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Jan 7, 2015; 21(1): 377-378
Published online Jan 7, 2015. doi: 10.3748/wjg.v21.i1.377
Re: ''Laparoscopic vs open approach to resection of hepatocellular carcinoma in patients with known cirrhosis: Systematic review and meta-analysis''
Zhan-Zhan Li, Li-Zhang Chen
Zhan-Zhan Li, Li-Zhang Chen, Department of Epidemiology and Health Statistics, School of Public Health, Central South University, Changsha 410078, Hunan Province, China
Author contributions: Li ZZ and Chen LZ conceived the study, participated in the study design, collected the data, and drafted the manuscript; all authors read and approved the final manuscript.
Supported by Hunan Province Science and Technology Project, No. 2014SK2013; Fundamental Research Funds for the Central Universities of Central South University, No. 2014zzts069
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: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Li-Zhang Chen, PhD, Department of Epidemiology and Health Statistics, School of Public Health, Central South University, No. 238 Shang Ma Yuan Ling Xiang Xiangya Road, Kaifu District, Changsha 410078, Hunan Province, China. liche4005@126.com
Telephone: +86-731-88836996 Fax: +86-731-88836162
Received: July 7, 2014
Peer-review started: July 8, 2014
First decision: August 6, 2014
Revised: August 23, 2014
Accepted: September 29, 2014
Article in press: September 30, 2014
Published online: January 7, 2015
Processing time: 183 Days and 14 Hours
Core Tip

Core tip: The combination of effect sizes in the meta-analysis is based on several factors: type of design of included studies, type of data, heterogeneity among studies, numerical stability and accuracy and understandability of results. For continuous variables, the standard mean difference is recommended when different measurement scales in the studies are used to reflect the outcomes. However, the weighted mean difference is more suitable when studies included use the same scale to report the outcomes.