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Vol. 36. Núm. 2.
Páginas 183-184 (Marzo 2021)
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Vol. 36. Núm. 2.
Páginas 183-184 (Marzo 2021)
Letter to the Editor
Open Access
Relation between COVID-19 and Guillain-Barre syndrome in adults. Systematic review
Relación entre COVID-10 y sindrome Guillain-Barre en adultos. Revisión sistemática
F. Araya-Quintanillaa,b,
Autor para correspondencia

Corresponding author.
, I. Valdés-Orregoc, H. Gutiérrez-Espinozaa,c
a Rehabilitation in Health Research Center, CIRES, University of the Americas, Echaurren Street 140, 3rd Floor, Santiago, Chile
b Faculty of Health, University SEK, Fernando Manterola Street 0789, Santiago, Chile
c School of Health Sciences, Physiotherapy Department, Universidad Gabriela Mistral, Santiago, Chile
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Dear Editor:

We read with interest the recent systematic review entitled “Relation between COVID-19 and Guillain-Barré syndrome in adults. Systematic review” by Trujillo-Gittermann et al.1 However, although the authors reported that they conducted the review following recommendations of PRISMA guidelines,2 there are some important departures, which have likely introduced biases and inconsistencies we would like to draw attention.

Our first concern is the questionable way to developed the Systematic Review (SR), the authors mention in the objective: “to analyze the evidence on the associations between COVID-19 and Guillan-Barré Syndrome (GBS)” and in your selection studies only included case reports, design with a lower level of evidence and that does not allow to establish associations between outcomes measures.3 Furthermore, they do not register the protocol in PROSPERO and do not take as reference the Cochrane Handbook to avoid selective reporting bias.4,5

Secondly, the authors not reported the risk of bias or methodological quality of studies included, introducing another bias in the quality of the SR, since it is suggested, evaluating and reporting these aspects in a complete way to see the quality of the studies in a SR.4,6

Regarding to the search strategy, draws attention to the flow chart diagram shown, is too general, the number of studies found by each database and the reasons for excluding studies are not reported, which makes a confusing interpretation. Furthermore, it does not report a sensitive search strategy that is required in a SR, not does it report how the [MesH] terms or “free text terms” were combined in all the databases.7 Elements required by the PRISMA guidelines and Cochrane Handbook to prevent publication bias.2,4,8,9

On close inspection of the raw data used, it can be seen that there is only a descriptive analysis of the studies, which does not allow to demonstrate categorical conclusions such as “We found a strong association between both conditions…” like in the SR.1 Moreover, if you want to show an association in a SR, you most select observational studies with effect estimators for these designs and should be performed a meta-regression analysis.10,11

Due to this, error may be observed in the selection, results and reports. Therefore, the results in this SR can influence the conclusion and findings of the study, Finally, the decisions or associations on its use need to be based upon unbiased summaries of the available evidence, therefore, your results should be interpreted with caution


The authors received no financial support for the research, authorship, and/or publication of this article.

Conflict of interest

The author (s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

L.M. Trujillo Gittermann, S.N. Valenzuela Feris, von Oetinger Giacoman.
Relation between COVID-19 and Guillain-Barré syndrome in adults. Systematic review [published online ahead of print, 2020 Jul 24].
A. Liberati, D.G. Altman, J. Tetzlaff, C. Mulrow, P.C. Gøtzsche, J.P. Ioannidis, et al.
The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate healthcare interventions: explanation and elaboration.
BMJ., 21 (2009), pp. b2700
D.A. Grimes, K.F. Schulz.
An overview of clinical research: the lay of the land.
Higgins JPT, Thomas J, Chandler J, Cumpston M, Li T, Page MJ, et al. (eds.), Cochrane Handbook for Systematic Reviews of Interventions version 6.0 (updated July 2019). Cochrane, 2019. Available from: www.training.cochrane.org/handbook.
F. Saric, O. Barcot, L. Puljak.
Risk of bias assessments for selective reporting were inadequate in the majority of Cochrane reviews.
J Clin Epidemiol, 112 (2019), pp. 53-58
M. Pollock, R.M. Fernandes, L. Hartling.
Evaluation of AMSTAR to assess the methodological quality of systematic reviews in overviews of reviews of healthcare interventions.
BMC Med Res Methodol, 17 (2017), pp. 48
V.M. Montori, N.L. Wilczynski, D. Morgan, R.B. Haynes, Hedges Team.
Optimal search strategies for retrieving systematic reviews from Medline: analytical survey.
B. Hutton, G. Salanti, D.M. Caldwell, et al.
The PRISMA extension statement for reporting of systematic reviews incorporating network meta-analyses of health care interventions: checklist and explanations.
Ann Intern Med, 162 (2015), pp. 777-784
L. Lin, H. Chu.
Quantifying publication bias in meta-analysis.
Biometrics, 74 (2018), pp. 785-794
D. Jackson, R. Turner, K. Rhodes, et al.
Methods for calculating confidence and credible intervals for the residual between-study variance in random effects meta-regression models.
BMC Med Res Methodol, 14 (2014), pp. 103
J.P. Jansen, S. Cope.
Meta-regression models to address heterogeneity and inconsistency in network meta-analysis of survival outcomes.
BMC Med Res Methodol, 12 (2012), pp. 152
Copyright © 2020. Sociedad Española de Neurología
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