Estimation of Serum Calcium on the Severity and Mortality in COVID-19 Infections in Sulaymaniyah City, Kurdistan Region of Iraq: A Cross-Sectional Study

Round 1

Reviewer 1 Report

This is a transversal study regarding the relationship between calcium concentration and COVID-19 Severity, which represents an addition to the issue of searching for cheap and accesible biomarkers for COVID-19 severity and outcomes; however, there are several issues regarding the methods and results:

1) Apparently only the total calcium was considered and there are no results using ionized or corrected calcium. Given that the authors comment on the fact that calcium may be affected by albumin and severe COVID-19 and sepsis is related to liver functiont test abnormalities, they should clarify as to why they used only total calcium. 

2) There are no results regarding other important biomarkers of severity for COVID-19 (including laboratory or imaging) in order to classify the patients in different groups

3) there is no information regarding the patients' comorbidities, which may affect the calcium concentrations, including kidney or liver disease, use of diuretics or calcium as well as other drugs

4) the only difference found by the authors was that female patients had a higher proportion of hypocalcemia than men (61 vs 34%), but table 1 does not show a significance for this difference and why there is a difference at all. An evaluation between men and women (age, BMI, medications, comorbidities, severity, etc.) may be necessary to clarify this point. 

5) figure 2 and tables 3 and 4 seem unnecesary because they don't provide any additional information and the results can be written in short sentences. It would be more interesting to provide a table comparing male vs female, the characteristics of patients with low calcium vs normal, etc.

6) If the only endpoint is to associate calcium levels to severity of COVID-19 there should be a clear definition of severity and maybe a comparison between low calcium and normal calcium and the percetage of Severe COVID. 

7) reference 15 is mentioned in the methods but it related to an article about breast cancer and hepatitits B which is not related to the topic at hand. The quality of PCR testing can therefore not be evaluated 

8)Authors do not mention either the moment at which the calcium was evaluated, given that if the patient has been hospitalized for several days before the sampling, treatments are also relevant for the calcium concentration. 

9) References 13 & 16 are not formatted correctly 

Author Response

Comments and Suggestions for Authors

This is a transversal study regarding the relationship between calcium concentration and COVID-19 Severity, which represents an addition to the issue of searching for cheap and accesible biomarkers for COVID-19 severity and outcomes; however, there are several issues regarding the methods and results:

Dear respected reviewer many thanks for your time to assess our manuscript. Your comments and suggestions were very significant to improve the quality of the work. We have revised our manuscript based on your comments. Responses to individual comments are given below and all changes in the manuscript are highlighted in yellow.

• Apparently only the total calcium was considered and there are no results using ionized or corrected calcium. Given that the authors comment on the fact that calcium may be affected by albumin and severe COVID-19 and sepsis is related to liver function test abnormalities, they should clarify as to why they used only total calcium. 

Dear reviewer thanks for this point. You are correct the calcium levels may be affected by albumin and severe COVID-19 and sepsis are related to liver function test abnormalities. We asked all the patients regarding their liver and kidney problems, they had no history of these diseases. Only five patients had underlying diseases namely cardiovascular diseases, diabetes, and hypertension. Also, the characteristics of COVID-19 gastrointestinal symptoms are subtler than those of COVID-19 respiratory symptoms, making them easy to ignore for all patients.  

• There are no results regarding other important biomarkers of severity for COVID-19 (including laboratory or imaging) in order to classify the patients in different groups.

Dear reviewer thanks for this notice, regarding the other biomarkers such as imaging, we are really sorry we couldn’t get the CT- scan for all patients. As you know this is a cross-sectional study, and we are not following the patients to test other biomarkers, hopefully, we will do that for our future works. Meanwhile, all of the patients were tested positive as having COVID-19 infection via analyzing a sample from a nasopharyngeal swab and performing real-time reverse transcription-polymerase chain reaction (RT-PCR).

• there is no information regarding the patients' comorbidities, which may affect the calcium concentrations, including kidney or liver disease, use of diuretics or calcium as well as other drugs.

Dear reviewer thanks for this point. We asked all the patients about their liver and kidney problems, they had no history of these diseases. An extra explanation has been added to the revised manuscript and all the changes are highlighted in yellow.

4) the only difference found by the authors was that female patients had a higher proportion of hypocalcemia than men (61 vs 34%), but table 1 does not show a significance for this difference and why there is a difference at all. An evaluation between men and women (age, BMI, medications, comorbidities, severity, etc.) may be necessary to clarify this point. 

Dear reviewer thanks for this important point. Table 4 illustrates that there is a mean difference between male and female calcium, as Levene's Test P-vale = 0.02 less than alpha 0.05, indicating that male and female calcium are not equal and there is a significant difference between them.

5) figure 2 and tables 3 and 4 seem unnecesary because they don't provide any additional information and the results can be written in short sentences. It would be more interesting to provide a table comparing male vs female, the characteristics of patients with low calcium vs normal, etc.

Dear reviewer thanks for this comment. In fact, table 3 displays a static analysis of one sample T-Test for serum calcium while table 4 shows an Independent sample test for serum calcium according to gender. Also, the age effect on to calcium levels are presented in Figure 2.

6) If the only endpoint is to associate calcium levels to severity of COVID-19 there should be a clear definition of severity and maybe a comparison between low calcium and normal calcium and the percetage of Severe COVID. 

Dear reviewer, many thanks for highlighting this. Male vs female comparisons based on the characteristics of patients with low calcium vs normal are well defined in the revised manuscript. Due to the patients were under intensive care in the hospital we couldn’t detect the percentage of sever COVID.

7) reference 15 is mentioned in the methods but it related to an article about breast cancer and hepatitits B which is not related to the topic at hand. The quality of PCR testing can therefore not be evaluated 

Dear reviewer thanks for this crucial note, and sorry for the mistake. The reference list is updated and re-arranged according to the journal style.

8)Authors do not mention either the moment at which the calcium was evaluated, given that if the patient has been hospitalized for several days before the sampling, treatments are also relevant for the calcium concentration. 

Dear reviewer thanks for this important comment, we would like to inform you that all the blood samples were taken from patients immediately after being admitted to the hospital and tested positive.

9) References 13 & 16 are not formatted correctly 

Dear reviewer thanks for this note, and sorry for the mistake. The reference list is updated and re-arranged according to the journal style.

 

Again, we would like to thank you for the wonderful and positive comments from the reviewers. Any changes or addition of words have been highlighted in yellow. We hope that our revised manuscript can now be accepted for publication.

Reviewer 2 Report

The manuscript has serious flaws. Please refer to the Abstract session for marked comments/suggestions/corrections as an example.

Comments for author File: Comments.pdf

Author Response

Reviewer #2

comments and Suggestions for Authors

The manuscript has serious flaws. Please refer to the Abstract session for marked comments/suggestions/corrections as an example.

Dear respected reviewer, we would like to thank you for your careful and thorough reading of this manuscript and for the thoughtful comments and constructive suggestions, which help to improve the quality of this manuscript. We have revised our manuscript based on your comments. All changes in the manuscript are highlighted in yellow.

Again, we would like to thank you for the wonderful and positive comments from the reviewers. Any changes or addition of words have been highlighted in yellow. We hope that our revised manuscript can now be accepted for publication.

Reviewer 3 Report

The work presented by Jihad M. Hadi and et al. title “Estimation of Serum Calcium on the Severity and Mortality in COVID-19 Infections in Sulaymaniyah City, Kurdistan Region of Iraq: A cross-sectional study” is well-written, clear, and easy to read. The topic is very interesting and actual. In particular, the author performed very well-conceived clinical trials about the infection due to the pandemic.

 

Just a note that I think is important to insert and discuss in the proper section please see  https://doi.org/10.3390/nu13113932,  https://doi.org/10.3390/reports4020018

Author Response

Reviewer #3

 

Comments and Suggestions for Authors

The work presented by Jihad M. Hadi and et al. title “Estimation of Serum Calcium on the Severity and Mortality in COVID-19 Infections in Sulaymaniyah City, Kurdistan Region of Iraq: A cross-sectional study” is well-written, clear, and easy to read. The topic is very interesting and actual. In particular, the author performed very well-conceived clinical trials about the infection due to the pandemic.

 

Just a note that I think is important to insert and discuss in the proper section please see  https://doi.org/10.3390/nu13113932,  https://doi.org/10.3390/reports4020018

Dear respected reviewer many thanks for the time to assess our manuscript. Your comments and suggestions were very significant to improve the quality of the work. We are really glad to hear that our manuscript is well-written, clear, and easy to read, and our topic was found to be very interesting and actual. Thank you very much for providing the references, we have cited your provided reference. It was very helpful in improving our manuscript and all changes in the manuscript are highlighted in yellow.

Again, we would like to thank you for the wonderful and positive comments from the reviewers. Any changes or addition of words have been highlighted in yellow. We hope that our revised manuscript can now be accepted for publication.

Reviewer 4 Report

This interesting cross-sectional study aimed to the association between calcium levels and COVID-19 severity. 

The authors should check the writing of the full text: for example line 47 "these virus" should be replaced with "this virus".

Line 77-84. The Authors should indicate other laboratory tests and relative references. Importantly, Napolitano F et al proposed soluble urokinase receptor (suPAR) as a serum biomarker of clinical severity in COVID-19 patients [Napolitano F et al, 2021 J Clin Med].

Author Response

Reviewer #4

 

Comments and Suggestions for Authors

This interesting cross-sectional study aimed to the association between calcium levels and COVID-19 severity. 

The authors should check the writing of the full text: for example line 47 "these virus" should be replaced with "this virus".

Line 77-84. The Authors should indicate other laboratory tests and relative references. Importantly, Napolitano F et al proposed soluble urokinase receptor (suPAR) as a serum biomarker of clinical severity in COVID-19 patients [Napolitano F et al, 2021 J Clin Med].

Dear reviewer thanks for your time and detailed evaluation on our manuscript. The offered comments and suggestions are very helpful. Following your suggestion, we corrected the mentioned mistakes and revised the manuscript thoroughly and accurately. Thank you very much for providing the references, we have cited all your provided references. It was very helpful in improving our manuscript and all changes in the manuscript are highlighted in yellow.

Again, we would like to thank you for the wonderful and positive comments from the reviewers. Any changes or addition of words have been highlighted in yellow. We hope that our revised manuscript can now be accepted for publication

Round 2

Reviewer 2 Report

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