Underreporting of Cases in the COVID-19 Outbreak of Borriana (Spain) during Mass Gathering Events in March 2020: A Cross-Sectional Study

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you for the opportunity to review this article. I believe that the topic is quite relevant, since the healthcare systems of various countries must be prepared for the development of pandemics and have the appropriate resources, including diagnostic capabilities. I have several comments: 1) In the introduction, the authors mention unreported deaths from coronavirus infection, but the article does not provide such information. Were there such deaths in the study region?; 2) In the Materials and Methods chapter, the principle of selecting patients for the study group is unclear. Of the 536 laboratory-confirmed cases of COVID-19, only 34 cases underwent PCR testing. Did they have symptoms of infection? What about the remaining patients whose diagnosis was confirmed? Did they have symptoms of the disease and if so, what were they? Did they have a CT scan of their lungs? The PCR reaction may be negative, but all signs of COVID-19 associated pneumonia may be present. There is no such information in the manuscript. The patient selection scheme could be presented in the form of a figure.; 3) Figure 1 needs a clear explanation; 4) It is not clear how the telephone survey of people who had the infection was conducted. It is necessary to present the methodology of such a survey and its results. 5) in the Conclusion section, the authors write about the need to prepare for possible pandemics, but do not say anything about the methods of such preparation based on the results of the study.

Author Response

Reviewer 1

Thank you for the opportunity to review this article. I believe that the topic is quite relevant, since the healthcare systems of various countries must be prepared for the development of pandemics and have the appropriate resources, including diagnostic capabilities. I have several comments: 1) In the introduction, the authors mention unreported deaths from coronavirus infection, but the article does not provide such information. Were there such deaths in the study region?; 2) In the Materials and Methods chapter, the principle of selecting patients for the study group is unclear. Of the 536 laboratory-confirmed cases of COVID-19, only 34 cases underwent PCR testing. Did they have symptoms of infection? What about the remaining patients whose diagnosis was confirmed? Did they have symptoms of the disease and if so, what were they? Did they have a CT scan of their lungs? The PCR reaction may be negative, but all signs of COVID-19 associated pneumonia may be present. There is no such information in the manuscript. The patient selection scheme could be presented in the form of a figure.; 3) Figure 1 needs a clear explanation; 4) It is not clear how the telephone survey of people who had the infection was conducted. It is necessary to present the methodology of such a survey and its results. 5) in the Conclusion section, the authors write about the need to prepare for possible pandemics, but do not say anything about the methods of such preparation based on the results of the study.

Thank you very much for the review of our manuscript.  We appreciate your suggestions and indications. For our response, we have separated all the questions.  

1) In the introduction, the authors mention unreported deaths from coronavirus infection, but the article does not provide such information. Were there such deaths in the study region?;

Thank you for questions. We reported deaths from COVID-19 in Borriana and Castelló de la Plana during January-June 2020.

2) In the Materials and Methods chapter, the principle of selecting patients for the study group is unclear. Of the 536 laboratory-confirmed cases of COVID-19, only 34 cases underwent PCR testing. Did they have symptoms of infection?

Thank you very much for your comments. The 536 laboratory confirmed cases of COVID-19 had suffered symptoms of illness. Asymptomatic cases were excluded. We have included Figure 2 with the flow diagram to clarify this issue.

2.1) Did they have symptoms of the disease and if so, what were they?

We have added Table 1 to compare COVID-19 symptoms between reported and unreported cases.

2.2) Did they have a CT scan of their lungs? The PCR reaction may be negative, but all signs of COVID-19 associated pneumonia may be present. There is no such information in the manuscript.

We don`t have information about the issue. However, the 2.4 % of cases have pneumonia and radiographic studies in hospitalized patients were performed. In addition, PCR and serological studies are considered the laboratory tests for SARS-CoV-2 confirmation.

2.3) The patient selection scheme could be presented in the form of a figure.

Thank you very much for your suggestion. We add this Figure 2 with the flow diagram of the study population in the mass gathering events in Borriana between January and June 2020.

3) Figure 1 needs a clear explanation;

Thank you very much for comment. Directed Acyclic Graphics (DAGs) was used to control potential confounding factors. We have explained this in Figure 1 with more detail.

4) It is not clear how the telephone survey of people who had the infection was conducted. It is necessary to present the methodology of such a survey and its results.

We appreciated this indication. We add information of the telephone survey, which was performed from May to June 2020, and in June the serological survey was implemented. This serological study permitted to confirm the cases of infection. All this have been described in the study of Domenech-Montoliu et al (1).

5) in the Conclusion section, the authors write about the need to prepare for possible pandemics, but do not say anything about the methods of such preparation based on the results of the study.

Thank you very much for your suggestion. We have added recommendations of some specific measures derived of our study. 

Reference

1.Domènech-Montoliu S, et al. "Mass gathering events and COVID-19 transmission in Borriana (Spain): A retrospective cohort study". PLoS One. 2021;16:e0256747.

 

Reviewer 2 Report

Comments and Suggestions for Authors

The study shows a high percentage in the similarity report, and it needs to be adjusted to be published. The introduction is too short and needs improvement. The presented results are insufficient to interest the medical audience; for publication, it is necessary to show more new information related to the reported medical aspects.

Author Response

Reviewer 2

The study shows a high percentage in the similarity report, and it needs to be adjusted to be published. The introduction is too short and needs improvement. The presented results are insufficient to interest the medical audience; for publication, it is necessary to show more new information related to the reported medical aspects.

Thank you for your review and your interest in our manuscript. Following your comments, we have augmented the introduction, and we have added more references. In addition, we have added new information of COVID-19 symptoms of the reported and unreported cases, and a flow diagram of the study population.  

Reviewer 3 Report

Comments and Suggestions for Authors

Reviewer Comments

Dear authors, it was a pleasure to read the study entitled: "Underreporting of cases in the COVID-19 outbreak of Borriana (Spain) during mass gathering events in March 2020: A cross-sectional study" by Salvador Domènech-Montoliu and colleagues with interest. Your topic is of some interest and the content of your manuscript is easy to follow.

However, conclusions should be posed with more caution in relation to the kind of data you used. Please find below my comments:

 

1.The manuscript could also benefit from further editing to remove some expressions that are not used in professional science communication. In general, the article could use some editing by someone experienced in scientific communication, particularly in English.

Some examples of imprecise language are as follows:

Introduction, lines 65-68. "In addition, it is of special interest in preparedness to future epidemics to adopt specific measures to know the causes and factors associated with the underreporting during the first wave of the COVID-19 pandemic." Clunky writing here.

Materials and Methods, lines 110-112. "Comparisons of variables between reported and underreported COVID-19 cases were made by Chi2 and Fisher exact tests for qualitative variables and Kruskal-Wallis for quantitative variables." It seems not precise and chunky here.

Results, lines 151-153. "Other factors concerting lifestyles such as obesity, smoking, alcohol intake, habitual physical exercise, and following a nutritional diet were not associated with the underreporting." Imprecise writing here.

 

2.In the Materials and Methods section, I strongly recommended you to define some of the lifestyle factors clearly. For example, please provide the type and intensity of your physical activity that were defined as habitual physical exercise. In addition, please specify the content of a nutritional diet, especially for the type of food and the frequency of such diet.

 

3.One general comment on the results of your manuscript: text often duplicates tables’ content, and the order of your results is a little confusing. I strongly advise you to simplify and adjust this section, as it complicates reading.

 

4.The tables were not standardized, it is recommended to put the first columns of the content in Table 1 and Table 2 left-sided alignment.

 

5.In the adjusted logistic regression model, you only adjusted for demographics information of the first two rows of Table 2, why? In order to better control the confounding factors, I advise you to adjust all the confounding factors in the adjusted model of your analysis, except for the effect modifier.

 

6.In the Discussion section, I suggest adding some appropriate content to the limitations section. It should include the reliance on a cross-sectional analysis, which might have an impact on causal direction.

Author Response

Reviewer 3.

Dear authors, it was a pleasure to read the study entitled: "Underreporting of cases in the COVID-19 outbreak of Borriana (Spain) during mass gathering events in March 2020: A cross-sectional study" by Salvador Domènech-Montoliu and colleagues with interest. Your topic is of some interest and the content of your manuscript is easy to follow. However, conclusions should be posed with more caution in relation to the kind of data you used. Please find below my comments:

 Thank you very much for your revision. We are grateful for your precise comments and suggestions.

1. The manuscript could also benefit from further editing to remove some expressions that are not used in professional science communication. In general, the article could use some editing by someone experienced in scientific communication, particularly in English. Some examples of imprecise language are as follows:

We have examined our study again, and an expert in English has reviewed the manuscript.

Introduction, lines 65-68. "In addition, it is of special interest in preparedness to future epidemics to adopt specific measures to know the causes and factors associated with the underreporting during the first wave of the COVID-19 pandemic." Clunky writing here.

Materials and Methods, lines 110-112. "Comparisons of variables between reported and underreported COVID-19 cases were made by Chi2 and Fisher exact tests for qualitative variables and Kruskal-Wallis for quantitative variables." It seems not precise and chunky here.

Results, lines 151-153. "Other factors concerting lifestyles such as obesity, smoking, alcohol intake, habitual physical exercise, and following a nutritional diet were not associated with the underreporting." Imprecise writing here.

Thank you very much for your comments. We have changed these phrases following the indications of the reviewer.

2.In the Materials and Methods section, I strongly recommended you to define some of the lifestyle factors clearly. For example, please provide the type and intensity of your physical activity that were defined as habitual physical exercise. In addition, please specify the content of a nutritional diet, especially for the type of food and the frequency of such diet.

Thank you very much for your suggestion. We add the questions for the lifestyle factors including habitual physical exercise and nutritional diet.

3. One general comment on the results of your manuscript: text often duplicates tables’ content, and the order of your results is a little confusing. I strongly advise you to simplify and adjust this section, as it complicates reading.

Thank you very much for your indications. We have made the simplifications.

4.The tables were not standardized, it is recommended to put the first columns of the content in Table 1 and Table 2 left-sided alignment.

Thank you very much for your indication. We have performed the left-side alignment.

 5.In the adjusted logistic regression model, you only adjusted for demographics information of the first two rows of Table 2, why? In order to better control the confounding factors, I advise you to adjust all the confounding factors in the adjusted model of your analysis, except for the effect modifier.

We appreciate these indications. Following our Directed Acyclic Graphics (DAGs) model, we have adjusted only for demographics information of the first two rows of Table 2, in order to know the association of demographics information with the underreporting of COVID-19 cases.  

We agree with the reviewer about the adjust for confounding factors, and we used the DAGitty v3.1 program of Textor J et al (1), and no medical assistance was adjusted for all potential confounding factors in our model. 

We have implemented a DAGs analysis for control of potential confounding factors, following Greenland, Pearl, and Robin (2), and Lederle et al (3). We have added these references to the manuscript for a better understanding.

 

6. 6. In the Discussion section, I suggest adding some appropriate content to the limitations It should include the reliance on a cross-sectional analysis, which might have an impact on causal direction.

Thank you for your indication. We add the cross-sectional design as other limitation of our study.

References

1.Textor, J.; van der Zander, B.; Gilthorpe, M.S.; Liskiewicz, M.; Ellison, G.T. Robust causal inference using directed acyclic graphs: the R package 'dagitty'. Int J Epidemiol 2016, 45, 1887-1894.

2. Greenland S, Pearl J, Robins JM. Causal diagrams for epidemiologic research. Epidemiology. 1999;10:37-48.

3.Lederer DJ, et al. Control of Confounding and Reporting of Results in Causal Inference Studies. Guidance for Authors from Editors of Respiratory, Sleep, and Critical Care Journals. Ann Am Thorac Soc. 2019;16:22-28.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

I am satisfied with the changes made to the article by the authors and the answers to my questions

Author Response

Reviewer 1

I am satisfied with the changes made to the article by the authors and the answers to my questions

Thank you very much for your comment. We have appreciated your indications.

 

Reviewer 2 Report

Comments and Suggestions for Authors

The article has only been partially improved according to the requirements, and the level of similarity is still too high (30%) to be published. I recommend the authors check the article with a professional plagiarism detection program before uploading it to the journal's website. The following observations are noted:
1. The article has too many authors,
2. Figures 1 and 2 need to be redone,
3. There are many formatting errors: extra spaces or missing spaces where they are needed,
4. The study number and approval date must be specified,
5. The conclusions need to be revised.

Author Response

Reviewer 2

The article has only been partially improved according to the requirements, and the level of similarity is still too high (30%) to be published. I recommend the authors check the article with a professional plagiarism detection program before uploading it to the journal's website. The following observations are noted:
1. The article has too many authors,
2. Figures 1 and 2 need to be redone,
3. There are many formatting errors: extra spaces or missing spaces where they are needed,
4. The study number and approval date must be specified,
5. The conclusions need to be revised.

Thank you very much for your observations.

We are increasing introduction, material and methods, and results. A new Table and a Figure are performed to improve the manuscript. In addition, the discussion has been completed. 

With respect to similarity, we have used the program https://plagiarismdetector.net/ to verify your indications, and we have changed and simplified some phrases. The level of similarity has reduced in a high proportion.

1.The article has too many authors,

All the authors have played a relevant role to make this study.

2. Figures 1 and 2 need to be redone,

The Figures 1 and 2 contributes with important information’s.  We think that are adequate in accordance with the first reviewer.

3. There are many formatting errors: extra spaces or missing spaces where they are needed,

We have reviewed the manuscript to correct these errors.

4. The study number and approval date must be specified,

The telephone survey study was approved in May 2020, and the serological survey on 11 June 2020, by the director Public Health Center of Castellon and the management of the Health Department of la Plana, considering the situation of the COVID-19 pandemic in the province of Castellon. No study number was indicated because no approval of an Ethic Committee was necessary (1)

 

5. The conclusions need to be revised.

Thank you for your comment. We change the conclusions following the abstract.

Reference

1. 1.Domènech-Montoliu S, et al. "Mass gathering events and COVID-19 transmission in Borriana (Spain): A retrospective cohort study". PLoS One. 2021;16:e0256747.