Letter to the Editor
Copyright ©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Meta-Anal. Aug 28, 2020; 8(4): 345-347
Published online Aug 28, 2020. doi: 10.13105/wjma.v8.i4.345
Integrating contextual variables in meta-analyses
Haitham Jahrami
Haitham Jahrami, Ministry of Health, Kingdom of Bahrain; College of Medicine and Medial Sciences, Arabian Gulf University, Manama P.O Box 26671, Bahrain
Author contributions: Jahrami H wrote this letter.
Conflict-of-interest statement: No conflict of interest.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (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/
Corresponding author: Haitham Jahrami, PhD, Assistant Professor, College of Medicine and Medial Sciences, Arabian Gulf University, Road 2904 Building 293 Manama, Manama PO Box 26671, Bahrain. hjahrami@health.gov.bh
Received: May 20, 2020
Peer-review started: May 20, 2020
First decision: July 4, 2020
Revised: July 4, 2020
Accepted: August 15, 2020
Article in press: August 15, 2020
Published online: August 28, 2020

Meta-analysis is an important statistical tool, and it is often used to solve clinical problems. However inevitably when conducting a meta-analysis, the included studies often have heterogeneity. This paper suggests the inclusion of relevant background data or contextual variables into the model. The contextual variables are those variables not explicitly measured in the studies included in a meta-analysis; thus, these must be very well-described and justified as parameters for analyses.

Keywords: Covariates, Moderator, Meta-analysis, Contextual, Subgroup analysis, Meta regression

Core Tip: This letter call for the use of contextual variables, that are typically not in use for covariate analyses. Contextual variables are introduced and defined as variables not immediately/directly measured by the original studies in the meta-analysis but rather can be estimated knowing the background of each study. For example in a meta analysis of clinical trails one might want to adjust for studies from high income vs low income countries or studies that were funded vs independent.