Neurology India
menu-bar5 Open access journal indexed with Index Medicus
  Users online: 6341  
 Home | Login 
About Editorial board Articlesmenu-bullet NSI Publicationsmenu-bullet Search Instructions Online Submission Subscribe Videos Etcetera Contact
  Navigate Here 
 Resource Links
    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
    Article in PDF (373 KB)
    Citation Manager
    Access Statistics
    Reader Comments
    Email Alert *
    Add to My List *
* Registration required (free)  

  In this Article

 Article Access Statistics
    PDF Downloaded89    
    Comments [Add]    
    Cited by others 3    

Recommend this journal


Table of Contents    
Year : 2016  |  Volume : 64  |  Issue : 4  |  Page : 840

Interpreting forest plots and funnel plots in meta-analysis

Department of Community Medicine, Dr. RP Government Medical College Tanda, Kangra, India

Date of Web Publication5-Jul-2016

Correspondence Address:
Sunil K Raina
Department of Community Medicine, Dr. RP Government Medical College Tanda, Kangra
Login to access the Email id

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0028-3886.185366

Rights and Permissions

How to cite this article:
Raina SK. Interpreting forest plots and funnel plots in meta-analysis. Neurol India 2016;64:840

How to cite this URL:
Raina SK. Interpreting forest plots and funnel plots in meta-analysis. Neurol India [serial online] 2016 [cited 2022 Aug 13];64:840. Available from: https://www.neurologyindia.com/text.asp?2016/64/4/840/185366


I went through with interest the article entitled “Rheumatoid arthritis and the risk of dementia: A systematic review and meta-analysis” published in Neurology India (2016;64:56-61).[1] Studies based on systematic reviews are an important means of summarizing the methods and results of individual studies.[2] Systematic reviews are being increasingly used in the development of clinical practice as well as the starting and ending point of randomized trials.[2] The authors, therefore, deserve credit for their effort. The authors have resorted to display of forest plot and funnel plot for interpretation of the results of their study, which is an accepted standard for conducting systematic reviews and meta-analyses. In this, the methodology used by the authors is correct. Herein, however, I would like to share a few concerns with the authors.

The authors in the past have emphasized the use of forest plots only when there are sufficient studies to make them of value, although this has not been defined.[2] However, it appears (from the forest plot) that inclusion of only five studies may be slightly on the lower side to derive the benefits of drawing a forest plot for the interpretation of results.

This takes me to my second point of concern. The authors report in their 'Results' section that the visualization of the funnel plot did not provide suggestive evidence for publication bias because the graph was symmetric. The authors further resort to Egger's regression test (P = 0.65), and quite correctly so, to establish any publication bias. However, a look at the Cochrane review reveals that, as a rule of thumb, tests for funnel plot asymmetry should be used only when there are at least ten studies included in the meta-analysis. This, they state, is because when there are fewer studies, the power of the tests is too low to distinguish chance from real asymmetry. The Cochrane review further advocated that the tests for funnel plot asymmetry should not be used if all studies are of similar sizes (similar standard errors of intervention effect estimates). Importantly, the test proposed by Egger in 1997 may be used to test for funnel plot asymmetry (as has been done by the authors); however, the review suggests that the use of tests to assess the power of study with substantially fewer than 10 studies would be unwise.[3]

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Ungprasert P, Wijarnpreecha K, Thongprayoon C. Rheumatoid arthritis and the risk of dementia: A systematic review and meta-analysis. Neurol India 2016;64:56-61.  Back to cited text no. 1
[PUBMED]  Medknow Journal  
Schriger DL, Altman DG, Vetter JA, Heafner T, Moher D. Forest plots in reports of systematic reviews: Across-sectional study reviewing current practice. Int J Epidemiol 2010;39:421-9.  Back to cited text no. 2
Recommendations on testing for funnel plot asymmetry. Available from: http://handbook.cochrane.org/chapter_10/10_4_3_1_recommendations_on_testing_for_funnel_plot_asymmetry.htm. [Last accessed on 2016 Feb 05].  Back to cited text no. 3

This article has been cited by
1 Association Between ZNF804A Gene rs1344706 Polymorphism and Brain Functions in Healthy Individuals: A Systematic Review and Voxel-Based Meta-Analysis
Liqiong Yang, Fan Xu, Yi He, Yanzhang Li, Zi Chen, Shuai Wang
Neuropsychiatric Disease and Treatment. 2021; Volume 17: 2925
[Pubmed] | [DOI]
2 Author-Based versus Group-Based Systemic Reviews and Meta-Analysis
SunilK Raina
Neurology India. 2020; 68(1): 204
[Pubmed] | [DOI]
3 A Comparison of Complications and Clinical and Radiologic Outcome Between the Mini-open Prepsoas and Mini-open Transpsoas Approaches for Lumbar Interbody Fusion
Alexander Spiessberger, Varun Arvind, Nicholas Dietz, Basil Grueter, Florian Huber, Roman Guggenberger, Bernhard Moriggl, Vikas Varma, Samuel K. Cho
Clinical Spine Surgery: A Spine Publication. 2020; 33(7): 271
[Pubmed] | [DOI]


Print this article  Email this article
Online since 20th March '04
Published by Wolters Kluwer - Medknow