PONE-D-22-31470Hospital services utilisation and cost before and after COVID-19 hospital treatment: evidence from IndonesiaPLOS ONE

Dear Dr. Firdaus Hafidz,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

==============================

Please submit your revised manuscript by May 06 2023 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

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If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

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We look forward to receiving your revised manuscript.

With Kind Regards,

Asst. Prof. Dr. Nemer Badwan

PhD in Economics and Finance

Assistant Professor of Economics and Finance

Academic Editor

PLOS ONE

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: No

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4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: This paper presents important information on hospital services utilization and cost before and after COVID-19 hospital treatment. The article is well written but there is some minor editing required. Also, I have highlighted a few areas of concerns in the submitted manuscript (see uploaded attachment.

Reviewer #2: This is an informative and well written article. There are a number of suggestions for strengthening the content and findings.

1. In the introduction and discussion I would like to see more information on the population based epidemiology of covid-19 for Indonesia. This will help to better understand the landscape at this time. This study occurred during the first surges globally and the incidence and prevalence of the condition and other demographic characteristics of those effected and uneffected would be useful to see.

2. The data is based upon a large administrative data base from Indonesia subjects included "with 28,159 Indonesian NHI enrollees treated with laboratory-confirmed COVID-19, compared with 8,995 individuals never diagnosed with COVID-19 in 2020." The methods used for laboratory confirmed Covid-19 dx is not described in detail. Was this according to the WHO criteria for diagnosing Covid-19. In addition, as this was based upon national data, were the laboratory methods across the country uniform and standardized?

3. More detail is needed for understanding the Covid-19 positive and "never diagnosed" groups. What is the level of comparability for the two groups (covid positive and "never diagnosed" beingcompared). Perhaps a propensity analysis would be useful to better understand the distance for all of the sociodemographic variables included to best understand the differences between the two groups compared. When matching I would base this on the Mahalanobis distance (MD), with the selection of the caliper. The study is only as good as an indepth understanding of the control group.

4. For the control group, what is meant by "never diagnosed." Does this mean that those in the control group received the Covid-19 test and were negative? Is it possible that there was a fraction of individuals in the control group that were positive for covid?

4. An instrumental variable analysis might be useful to better understand unmeasured variables that go uncontrolled for in the analysis? What might such unmeasured variables be?

5. As this study was done during the earlier surges of the global pandemic it would be useful to understand the severity of the presenting covid-19 and if data is available have a breakdown of costs and hospitalizations for those severely impacted.

6. The focus for stratifications for hospital costs of services is by age (< 40 and >= 40). How was 40 years of age selected as the cutoff? Could more stratifications be included for age by a younger age group and the elderly? Results may be interesting. Can additional stratifications for other variables be included such as gender and educational level (a proxy for income).

7. I would like to see the Indonesian currency "Rupiahs" converted to US dollars. Or at least a footnote indicating the conversion rate.

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Reviewer #1: Yes: Adebola Emmanuel Orimadegun

Reviewer #2: No

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Attachments

Attachment

Submitted filename: PONE-D-22-31470_reviewer.pdf

PONE-D-22-31470R1Hospital services utilisation and cost before and after COVID-19 hospital treatment: evidence from IndonesiaPLOS ONE

Dear Dr. Firdaus Hafidz,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please submit your revised manuscript by Oct 16 2023 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

• A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind Regards,

Asst. Prof. Dr. Nemer Badwan

PhD in Economics and Finance 

Assistant Professor of Economics and Finance

Academic Editor

PLOS ONE

Journal Requirements:

Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #3: (No Response)

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #3: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #3: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #3: No

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #3: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: (No Response)

Reviewer #3: The authors conducted a retrospective study on parameters related to COVID-19 healthcare in Indonesia. The idea to focus on periods before or after treatment of COVID-19 patients is highly interesting. Scope and idea of the study are clearly described. The study is relevant for understanding the pandemic’s impact of the pandemic on the healthcare system.

Comments/questions:

1. I suppose “COVID-19” here is defined as a lab-confirmed SARS-CoV-2 infection. Are information available that allow for identifying patients who actually developed corresponding respiratory systems? What might be the influence of patients without SARI?

2. If “COVID-19” were indeed defined as SARS-CoV-2 infection, I would recommend including SARI as a comorbidity too.

3. How does hospital service utilization enter the statistical models? Is it a binary variable or a count per month? What kind of model was used, logistic or Poisson regression? Please add more details.

4. Is a linear model used for total claims (costs)? Did you check the distribution of costs? Was the variable transformed before entering the model? In my experience, this variable is highly skewed. Please add more details.

5. The model formula (line 146) contains two coefficients, alpha and beta. I suppose the regression estimated coefficients for the other covariates too. If this is true, please extend the formula.

6. The model formula appears to contain interaction terms between the month and several covariates (age, sex, comorbidities). Did the model also contain terms for main effects of these covariates?

7. I would like to know whether the authors did conduct the analyses stratified for total, age groups, and sex.

8. The authors present the proportions of different comorbidities. Are these comorbidities derived from ICD codes?

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7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: Yes: Adebola E. Orimadegun

Reviewer #3: No

**********

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.<quillbot-extension-portal></quillbot-extension-portal>

PONE-D-22-31470R2Hospital services utilisation and cost before and after COVID-19 hospital treatment: evidence from IndonesiaPLOS ONE

Dear Dr. Hafidz,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

==============================

Please submit your revised manuscript by Dec 01 2023 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

• A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Asst. Prof. Dr. Nemer Badwan, Ph.D in Economics and Finance

Academic Editor

PLOS ONE

Journal Requirements:

Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

[Note: HTML markup is below. Please do not edit.]

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

PONE-D-22-31470R3Hospital services utilisation and cost before and after COVID-19 hospital treatment: evidence from IndonesiaPLOS ONE

Dear Dr. Hafidz,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

==============================

Please submit your revised manuscript by Jan 20 2024 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

• A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes should be uploaded as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions, see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind Regards,

Asst. Prof. Dr. Nemer Badwan

Ph.D in Economics and Finance

Assistant Professor of Economics and Finance

Academic Editor

PLOS ONE

[Note: HTML markup is below.] [Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #5: (No Response)

Reviewer #6: (No Response)

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #5: Partly

Reviewer #6: Partly

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #5: Yes

Reviewer #6: Yes

**********

4. Have the authors made all the data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with a rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g., participant privacy or use of data from a third party—those must be specified.

Reviewer #5: Yes

Reviewer #6: No

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #5: Yes

Reviewer #6: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters.)

Reviewer #5: Major comments:

- Choice of reference period? What is the rationale for using the fifth month for hospital utilization and the 4-6 months before for cost? If you had chosen one month prior to hospitalization, the results would have been different. Why is the period in February used as comparison group?

- Is the aim of the study to investigate the utilization and cost for the ‘patients with COVID’ or the ‘COVID-19 disease’ itself? See the following text from your paper: “ We explored the short- to medium-term change in the pre- and post-acute period of COVID-19 treatment to fully understand the extent to which COVID-19 might be associated with the use of hospital services, especially in a resource-constrained setting.”

- I would like to include the crude rate of hospital utilization and cost, not only the estimated difference in the difference plot, to be sure of the assumption that the trend in outcome between the two groups was similar in the absence of COVID-19.

- I also want you to include the figures on the difference in the estimate for cost analysis and not only for health care utilization to see if the pre-trend assumption also holds here.

- In Figure 4 (in-patient, May period), I think the estimates of the difference are not zero in the months prior to the fifth month before COVID-19 treatment but rather increasing; this may be discussed in the Discussion section.

- Additionally, also you should also discuss what causes the increased use of health care and cost from 5 months before treatment; it is a long period, are these frail patients?

- And why are the patients older in the comparison group?

- There are more people in the comparison group with the non-subsidized membership scheme; could this affect health care utilization?

Minor comments:

- Please use the comparison group instead of the control group since it is not an RTC.

- Fig 1, misspelled in legend yellow, Months before COVID-10 hsopitalization

- Severity level: how are the different levels defined? Please include this information in the method section and in the table notation. Is this the same as the COVID-19 severity used as the control variable in the regression? And have all included patients with COVID-19 as their main cause of hospitalization, or could it also be that they were arbitrary was tested when admitted to the hospital?

- In figure 1, it is stated that "lines represented the estimated difference between the COVID-19 and 215 control groups, controlling for demographic characteristics," but the controlling variable is the same as stated in the tables: “Regressions control for individuals’ year of birth, gender, COVID-19 severity, NHI membership segment, comorbidities prior to 2020 interacted with the month indicator, as well as month and province fixed effects.” But in the data source section, the basic demographic characteristics included year of birth, sex, district and province, and type of NHI membership, but nothing about COVID-19 severity or comorbidity. Please indicate all controlling variables in the figure legends.

- Please be consistent with the word, like for instance, province or district instead of region, and COVID-severity instead of only severity.

- Use log-transformed values of the cost variables. What are the results from the additional analysis? I can’t see that Table 2 includes these results. “ These results were similar when we used the log-transformed value of the cost variables (see Table 2).”

Reviewer #6: The study authors conducted an analysis comparing inpatient hospital visit rates, outpatient hospital visit rates, and hospital-associated costs associated with COVID-19-positive patients compared with controls who have not yet contracted COVID-19. I believe the study is methodologically sound, but this can be strengthened with more details regarding data sources and the statistical methods.

- Page 3 line 62: “with” instead of “which” or some rewording of this first sentence is needed

- Page 6 line 128: “in in”

- Page 9 line 184: range of age minimum is 44.2, not 44.6, if I’m reading this correctly

- It took me a while, but after studying Figure 1 and looking at the results, I believe I understand the methods. Please confirm if I’m understanding this correctly. If I am, then I think the methods can be written differently to more simply explain what was done and why

o The control group (unexposed) contracted COVID-19 eventually. This fact is the reason why this group was chosen as a control (as a means to adjust for some confounders)

o The case group (exposed) contracted COVID-19 earlier (2020)

o The difference between exposed and unexposed was determined by time period (-9, -8, 0, 1, …, 6)

- We would expect, on average, that the cases and controls are similar with respect to demographic and clinical characteristics. However, this is generally not true as COVID-19 changed over time (e.g., virulence), immunity changed, and public health mandates changed as well. Standardized differences are not reported but are probably meaningfully different between cases and controls during the “pre” period. DiD methods often use propensity score methods to adjust for such factors. Why was this not considered? This is particularly of concern when, using age as an example

- It appears that there is a lack of parallel trends for the inpatient analysis (Figure 4).

- It’s unclear how clustering was taken into account since the same patient can be found in the analysis multiple times. From the table captions, it seems like there was some adjustment, but I did not see this mentioned in the methods.

- An assumption was made on page 6 that “those who were treated in hospitals with COVID-19 in February 2021 were classified as the control group, assuming they never contracted COVID-19 in 2020," but it’s not clear why an assumption had to be made. Rather, couldn’t this have been verified from the data?

- If coefficient 0.1t represents the month-specific DiD, is this what’s reported in Table 2? It isn’t clear from the table descriptor or the description of the results in the prose. For example, the paragraph beginning on page 17, line 270, does not mention interaction in the interpretation.

- It is not specified in the methods by which cases of COVID-19 were captured or the accuracy of this. Different countries may have had differential access to PCR testing over time, and inpatient testing may be more accurately documented than outpatient testing.

- The descriptors of cost were not presented. What types of costs were captured?

- I don’t think using prior medical history to predict COVID-19 infection should be mentioned in the conclusions.

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Reviewer #5: No

Reviewer #6: No

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PONE-D-22-31470R4Hospital services utilization and cost before and after COVID-19 hospital treatment: evidence from IndonesiaPLOS ONE

Dear Dr. Hafidz,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please submit your revised manuscript by Apr 14 2024 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

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If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

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We look forward to receiving your revised manuscript.

Kind Regards,

Asst. Prof. Dr. Nemer Badwan 

Ph.D in Economics and Finance

Assistant Professor of Economics and Finance

Academic Editor and Reviewer 

PLOS ONE

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #5: All comments have been addressed

Reviewer #7: (No Response)

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #5: Yes

Reviewer #7: Partly

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #5: Yes

Reviewer #7: Yes

**********

4. Have the authors made all the data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with a rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information or deposited in a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g., participant privacy or use of data from a third party—those must be specified.

Reviewer #5: Yes

Reviewer #7: No

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #5: Yes

Reviewer #7: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters.)

Reviewer #5: Thanks for the answers to all my previous comments. I only have one additional comment.

Could you refer to all the S2 tables in the manuscript?

Reviewer #7: Review report on PONE-D-22-31470_R4: Hospital services utilization and cost before and after COVID-19 hospital treatment: evidence from Indonesia

The authors estimate health care utilization before and after PCR-confirmed SARS-CoV-2 in Indonesia in 2020 by contrasting the utilization of patients with COVID-19 in 2020 to the utilization of patients with COVID-19 in February 2021. They find elevated utilization around the time of infection, but no difference after four months.

The paper is well-written, and the statistical analyses appear well-executed. As noted by the authors, it is important to undertake studies using registry data in LMIC too, and this is a fine example thereof. Still, I believe the study suffers from a couple of fundamental concerns that need to be discussed more carefully and sincerely before the paper can be accepted for publication.

The construction of the treatment (covid-19) and comparison (not yet covid-19) is crucial for the interpretation of the results. The author states that “the comparison group comprised individuals treated for COVID-19 in hospitals in February 2021, under the presumption they had not contracted the virus in 2020” (line 115). This implies that what is estimated is not the impact (on subsequent utilization/costs) of having COVID-19 vs. not having COVID-19 in 2020, but the impact (on subsequent utilization/costs) of having COVID-19 in 2020 vs. having COVID-19 in 2021. This distinction has important implications for interpretation. For example, the authors’ DiD estimates how much higher the costs of treating a COVID-19 patient were in 2020 compared to 2021 (not the costs of treating a COVID-19 patient vs. not treating one). And, as another example, the authors do not shed any light on the presence of sequelae after SARS-CoV-2 infection, only on the question of whether possible sequelae are different in 2020 vs. 2021.

Clearly, these are two different questions (i. effects on utilization of COVID; ii. effects on utilization of COVID in 2020 vs. 2021), due, e.g., to the strain on health care services and other societal restrictions at the beginning of the pandemic. It seems obvious that the services’ ability to treat patients (both those with COVID-19 and other patients) was very different in 2020 than in 2021 (and definitely in 2024). It is crucial that the authors make this distinction between the two research questions clear to the readers (including in the abstract) and that they improve precision in how they describe their research question (and findings) throughout the paper (including considering making the title communicate this better).

In doing so, the authors may consider describing briefly other ways of constructing the comparison group and its implications for the research question, e.g., using contemporaneous patients with negative PCR tests (in 2020), like in reference (14), which would address the question of the impact of SARS-CoV-2 vs. no SARS-CoV-2 (instead of SARS-CoV-2 in 2020 vs. 2021). The authors should also be careful in pointing out the differences in research questions when comparing them with previous studies and when discussing policy implications (both in Discussion). This said, it appears to me that the question actually addressed by the authors' regressions (impact on utilization of COVID in 2020 vs. 2021) is of interest; it just needs to be stated and motivated clearly to the reader.

It seems that those dying are excluded from the sample, instead of the more common approach of censuring them from the month of death: “Similarly, those who died during COVID-19 hospitalization or in subsequent months were also excluded from the analysis.” (line 114). If medical treatment for COVID-19 was more effective in 2021 than in 2020 (e.g., due to less strain on the services or some immunity due to low-dose exposure or vaccination (too early for that in Indonesia?)), this introduces a potentially serious bias to the analysis: The comparison group receives more utilization because they survive longer (which would lead to an underestimation of how much higher costs were in 2020 than in 2021). This problem is not easy to handle, but it absolutely deserves a serious and sincere discussion. It would also be important to inform the reader of the survival in the two groups (i.e., by providing death rates by 3-6 months or even the impact on death using the same regressions). Was survival measured for the same length of time in the comparison group?

Minor things.

I do not understand why “individuals who were under monitoring and recorded as suspect or probable cases of COVID-19 in the previous months before laboratory confirmation were excluded” (line 113), since it makes the relevance of the results restricted to those who are actually being tested (which I presume could depend on the severity of the infection or socioeconomic status, or, as noted by the authors, that the hospital/patient have access to PCRs done by a Ministry of Health-accredited laboratory). On the other hand, I do not see that this has important methodological problems (except that PCR testing capacity was presumably smaller relative to the number of infections in 2020 than in February 2021) as long as the reader understands that the population under study is narrow. However, in note to Table 1, it is stated that “individuals without any hospital encounters before January 2020 (..) were excluded.” How is this incorporated for the comparison group in a way that does not introduce differences/bias across the two groups?

It would be very informative if Table 1 also included the outcome variables (i.e., the raw out- and inpatient rates and costs by, e.g., 3 months) and a reference to Supplement Table 2 for details (but this supplement table is not informative about the comparison group since we are only informed about post-infection months for the treated (not the comparison)—please fix).

Eq. 1 includes individual fixed effect (alpha i), but also a dummy for being in the treatment group (Covid i). I presume there is a typo here, as the individual fixed effect would absorb all other time-invariant individual characteristics (and, obviously, being in the treatment group does not change over time).

Given the vast population of Indonesia, some information on why there are so few people in the sample is warranted.

I don’t understand why the cost results are not also presented in a figure (like the nice figures for in- and outpatient results; please refer the reader to Supplement Table 1 in the note to these figures).

I was not able to reach the data application site using the link in the data sharing statement.

“before” is lacking in line 31 of the abstract.

Strictly speaking, the PCR test is for SARS-CoV-2 (i.e., the virus) and not for COVID-19 (the disease); the authors might consider their precision in the use of these two terms.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

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Reviewer #5: No

Reviewer #7: No

**********

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments.". [If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that supporting information files do not need this step.

PONE-D-22-31470R5Hospital services utilisation and cost before and after COVID-19 hospital treatment: evidence from IndonesiaPLOS ONE

Dear Dr. Hafidz,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

==============================

Dear author(s),

The seventh reviewer asked to amend all the main comments he requested in the fourth review round, and you did not amend what was required.

Either you are not convinced by those comments and are against them, or you did not fully understand what the reviewer wanted from you in order to amend it as necessary.

Therefore, I ask you to review the comments of the seventh reviewer, amend and include all the comments and concerns raised by the reviewer, and submit the manuscript for the sixth time for review.

Please carefully review all comments and do not ignore any of the comments already included in the previous peer review report.

Please see below the reviewer's 7 comments:

I'm not impressed by the authors' response to my comments and suggestions. They either do not want to understand my two main comments—and if so, they should say so or state that they disagree with me (which could be fine, of course)—or their understanding of the method they are applying (DID) is very shallow.

In particular, in responding to my first main comment on implications for interpretations of using 2021 cases as a comparison group, they keep repeating that they assume that the comparison group had not had COVID before. While I agree that this is an important assumption, my point was another one: The DID they run looks at how changes from before to after COVID differ for those having it in 2020 vs. 2021; see my prior report to the authors for elaboration.

I'm also not impressed with the shallow response to my second main comment.

Overall, I maintain my comment in my previous report that the interpretations they make do not sufficiently reflect the research question actually addressed by the method they in fact applied. As noted in my previous response to you, I do not think there is a need for new analyses, only that the interpretation and framing of the paper should align better with what the applied method (DID) is in fact addressing.

On the other hand, it seems to me that the authors have had to deal with 7 (?!) reviewers and a number of revisions, so I can understand if they are getting fed up with revising this paper. Thus, I see that making a decision on this paper can be a hard call for the editor.

==============================

Please submit your revised manuscript by Jun 01 2024 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

• A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind Regards,

Asst. Prof. Dr. Nemer Badwan

Ph.D in Economics and Finance

Academic Editor and Reviewer

PLOS ONE

Journal Requirements:

Additional Editor Comments (if provided):

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #5: All comments have been addressed

Reviewer #7: (No Response)

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #5: Yes

Reviewer #7: Partly

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #5: Yes

Reviewer #7: I Don't Know

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #5: Yes

Reviewer #7: No

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #5: Yes

Reviewer #7: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #5: (No Response)

Reviewer #7: (No Response)

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If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #5: No

Reviewer #7: No

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While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

Hospital services utilisation and cost before and after COVID-19 hospital treatment: evidence from Indonesia

PONE-D-22-31470R6

Dear Dr. Firdaus Hafidz,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice will be generated when your article is formally accepted. Please note, if your institution has a publishing partnership with PLOS and your article meets the relevant criteria, all or part of your publication costs will be covered. Please make sure your user information is up-to-date by logging into Editorial Manager at Editorial Manager® and clicking the ‘Update My Information' link at the top of the page. If you have any questions relating to publication charges, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind Regards,

Asst. Prof. Dr. Nemer Badwan 

Ph.D in Economics and Finance

Assistant Professor of Economics and Finance 

Academic Editor and Reviewer 

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #5: All comments have been addressed

Reviewer #8: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #5: Yes

Reviewer #8: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #5: Yes

Reviewer #8: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #5: Yes

Reviewer #8: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #5: Yes

Reviewer #8: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #5: I have reviewed this manuscript before, and it has improved during the revisions. I have no further comments.

Reviewer #8: Dear authors,

thank you for this opportunity to read "Hospital services utilisation and cost before and after COVID-19 hospital treatment: evidence from Indonesia". It was very clear and well written.

My only concern, and it is minor and should not delay publication, is that in future articles, please be clear about the average outpatient visit costs or per capita expenditure, by island, age, and gender, should be if people were in good health. Reviewing your supplemental tables assisted in my understanding of your paper. Reporting that information will help future readers understand the magnitude and burden of increased utilization on the Indonesian health system.

Overall, a good paper. I look forward to seeing it in print.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #5: No

Reviewer #8: No

**********