Lack of protective effect of chloroquine derivatives on COVID-19 disease in a Spanish sample of chronically treated patients
Laplana et al.
, Lack of protective effect of chloroquine derivatives on COVID-19 disease in a Spanish sample of chronically..
, PLOS ONE, doi:10.1371/journal.pone.0243598
Survey of 319 autoimmune disease patients taking CQ/HCQ with 5.3% COVID-19 incidence, compared to a control group from the general population (matched on age, sex, and region, but not adjusted for autoimmune disease), with 3.4% incidence.
It not clear why authors did not compare with autoimmune patients not on CQ/HCQ. Other research shows that the risk of COVID-19 for systemic autoimmune disease patients is much higher overall, Ferri et al. show OR 4.42, p
, which is the observed real-world risk, taking into account factors such as these patients potentially being more careful to avoid exposure. If we adjust for the different baseline risk, the result becomes RR 0.36, p
<0.001, suggesting a substantial benefit for HCQ/CQ treatment (as shown in other studies).
There may also be significant survey bias - those experiencing COVID-19 may be more likely to respond to the survey.
Authors note that they "could not eliminate completely the possibility of some bias due to the intrinsic condition of the individuals within the treatment group that are undergoing chloroquine or derivative drug treatment due to other diseases that alter their health status and may have different comorbidities", however they could account for one significant bias by comparing with matched autoimmune disease patients.
This study is excluded in the after exclusion results of meta
not fully adjusting for the different baseline risk of systemic autoimmune patients.
risk of case, 56.0% higher, RR 1.56, p = 0.24, treatment 17 of 319 (5.3%), control 11 of 319 (3.4%).
Effect extraction follows pre-specified rules prioritizing more serious outcomes. Submit updates
Laplana et al., 9 Sep 2020, retrospective, Spain, peer-reviewed, survey, 3 authors.
Abstract: PLOS ONE
Lack of protective effect of chloroquine
derivatives on COVID-19 disease in a Spanish
sample of chronically treated patients
Marina Laplana ID1, Oriol Yuguero2,3, Joan Fibla ID3,4*
1 Departament de Ciència Animal, Universitat de Lleida, Lleida, Spain, 2 Hospital Universitari Arnau de
Vilanova de Lleida, Lleida, Spain, 3 Institut de Recerca Biomedica de Lleida, Lleida, Spain, 4 Departament
de Ciències Mèdiques Bàsiques, Unitat de Genètica Humana, Lleida, Spain
Citation: Laplana M, Yuguero O, Fibla J (2020)
Lack of protective effect of chloroquine derivatives
on COVID-19 disease in a Spanish sample of
chronically treated patients. PLoS ONE 15(12):
Editor: Wenbin Tan, University of South Carolina,
Received: August 27, 2020
Accepted: November 24, 2020
The search for a SARS-CoV-2 treatment has emerged as a worldwide priority. We evaluated the role of chloroquine and its derivatives in COVID-19 in Spanish individuals.
We performed a survey addressed to patients regularly taking chloroquine and its derivatives for the control of their autoimmune diseases. The survey was distributed with special
attention to Spanish patient associations centred on autoimmune diseases and rheumatology and to the general population. A sample of untreated subjects was matched to the
treated group according to sex, age range and incidence region. COVID-19 disease prevalence was compared between treated and untreated-matched control sample.
Published: December 14, 2020
Peer Review History: PLOS recognizes the
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Copyright: © 2020 Laplana et al. This is an open
access article distributed under the terms of the
Creative Commons Attribution License, which
permits unrestricted use, distribution, and
reproduction in any medium, provided the original
author and source are credited.
Data Availability Statement: All relevant data are
within the manuscript and its Supporting
A total of 319 surveys of patients regularly taking chloroquine and its derivatives were recovered for further analysis. The prevalence of declared COVID-19 status in the treated group
was 5.3% and the mean prevalence among the untreated-matched groups was 3.4%. A
community exposition to COVID-19 was associated with a greater prevalence of COVID-19
in both, treated (17.0% vs. 3.2%; p-value<0.001) and untreated groups (13.4% vs. 1.1%; pvalue = 0.027).
We did not find differences of reported COVID-19 cases between treated and untreated
groups, indicating a lack of protection by regular administration of chloroquine and its derivative drugs on COVID-19 infection. Of relevance, data indicates that patients that regularly
take chloroquine derivatives are exposed to SARS-CoV-2 infection and must take the same
protection measures as the general population.
PLOS ONE | https://doi.org/10.1371/journal.pone.0243598 December 14, 2020
Funding: The author(s) received no specific
funding for this work.
Competing interests: The authors declare that the
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