Dear Dr. Melander,

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 Aug 19 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.

• 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'.
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We look forward to receiving your revised manuscript.

Kind regards,

Andreas Vilhelmsson, Ph.D

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?

Reviewer #1: Partly

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

Reviewer #1: No

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

The PLOS Data policy

Reviewer #1: Yes

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

Reviewer #1: Yes

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Reviewer #1: Thank you for providing the opportunity to review this paper, entitled "Swedish pediatric surgery during Covid: A national registry study on the effects of the pandemic on pediatric anesthesia and surgery ". Below, I have provided my evaluation and comments.

I request information about the data source (SPOR) in the method section. How is data recorded into the register? Is it done manually? Are SPOR validated? Most important, to what extent does SPOR cover all operations performed in Sweden? Do centers from both the public and private sectors report to SPOR? Tonsillectomy is often performed in private centers, and sometimes surgery is offered outside the patient's region. Could this impact the validity of the results?

The title contains "…anesthesia and surgery." However, the results do not focus on anesthesia. Are all surgical interventions included in the results performed under anesthesia or specifically general anesthesia? This needs to be clarified.

Only centers that had started reporting to SPOR before 2019 were included. Were all these centers reporting to SPOR throughout the entire period from 2019 to 2022? Or have some centers stopped reporting to the register due to increased workload during the pandemic? This needs to be clarified.

I also request information about the variables retrieved from SPOR and the data arrangement. For example, I find it hard to understand the calculation of the evolution of waiting times. This needs to be clarified in the manuscript.

The large volume of data analyzed means that even small differences can be statistically significant (which could be seen in the analysis of mean age at surgery). Therefore, the results need to be interpreted from the perspective of what is clinically relevant. However, under the statistical section, the significance level that was considered significant is missing.

Several data points appear to be wrong in the tables. For example, the data in Table 1, column 2019, row total-elective, appears to be incorrect (4,067?). The data in Table 3, column Tonsil surgery, row 2019, also seems wrong (1.6?). Please check all data presented in the manuscript.

The discussion is weak and needs to be revised. Some results are briefly discussed, and some statements are poorly substantiated. For instance, the text suggests that ENT surgeries, including tonsillectomy, can be postponed for months or even years without serious harm. The two main indications for tonsil surgery are upper airway obstruction, causing abnormal ventilation during sleep, and infection-related problems such as recurrent tonsillitis. Studies and national guidelines argue that these patients should be prioritized due to short- and long-term consequences of postponed surgery. The discussion section should acknowledge the potential harm of postponed surgeries.

I hope my comments can help!

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Reviewer #1: No

**********

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Dear Dr. Melander,

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 29 2025 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.

• 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,

Andreas Vilhelmsson, Ph.D

Academic Editor

PLOS ONE

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

Reviewer #1: All comments have been addressed

Reviewer #2: (No Response)

**********

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

Reviewer #1: Yes

Reviewer #2: Partly

**********

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

Reviewer #1: Yes

Reviewer #2: N/A

**********

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

The PLOS Data policy

Reviewer #1: Yes

Reviewer #2: No

**********

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

Reviewer #1: Yes

Reviewer #2: Yes

**********

Reviewer #1: (No Response)

Reviewer #2: This manuscript addresses an important and timely topic, contributing to our understanding of long-term healthcare implications post-COVID-19 on healthcare systems. It is a commendable effort to analyze data from a national cohort.

However, significant revisions are necessary to enhance the methodological rigor and ensure the claims are well-supported by the presented data. Specifically, the conclusions regarding long-term effects of COVID-19 require a more cautious interpretation, given the descriptive nature of the retrospective cohort study and potential biases in the analysis. Furthermore, a more robust time series analysis and careful control for confounding factors are critical to substantiate the findings.I do not agree with the concluding claim that the provided data is evidence for long-term effects of COVID-19, at least based on the evidence provided so far. We observe data indicating an increasing overall stress burden on healthcare worldwide due to various reason that also include i.e. changing demographics, rising costs etc.. These factors are and probably cannot addressed in a cohort study based on retrospective secondary data.

Introduction

1) Include more references; ensure all claims are supported by citations.

Methods

1) Report the methods and study characteristics more thoroughly.

2) Explain the rationale for selecting 2019 as the baseline year. Please adjust the research question and objectives accordingly. Elaborate on why comparisons were not made to an average of the years before.

3) Provide details of the study setting, including the exact number of study centers and the variables used for secondary analyses (e.g., level of care).

4) Include comprehensive details of the cohort, including eligibility criteria and the sources and methods of participant selection.

5) Clearly define all outcomes, exposures, predictors, potential confounders, and effect modifiers.

6) Expand on data sources and measurement methods, including a discussion of the registry as a secondary data source and its likely purpose for billing.

7) Describe efforts to address potential sources of bias in the registry or clarify if this is a convenience sample.

8) Explain how quantitative variables were handled in the analyses. If applicable, describe groupings and provide a rationale for the chosen groupings (e.g., why focus on the 20 most common procedures in 2019 rather than overall procedures?).

9) Provide the rationale for investigating the mean age at the time of surgery and how it relates to the study objectives.

10) Include more robust time-series analyses, such as interrupted time-series analysis (Especially given the claim in the conclusion).

10.1) Consider the influence of different COVID-19 waves, comparing them to baseline and different timings ((i.e. https://doi.org/10.1177/014107682096244, https://doi.org/10.1186/s12889-023-15375-7, https://doi.org/10.1371/journal.pgph.0000029).

10.2) Consider causal impact analysis (https://doi.org/10.2147/rmhp.s459307).

13) Explain how missing data were handled in the study.

14) Provide the r source code for the analysis.

Results

15) Clarify whether cases were excluded and provide details about the overall initial sample. Report the number of individuals at each stage of the study (e.g., eligible, examined for eligibility, confirmed eligible, included).

16) If possible, include a cohort flow chart detailing exclusions and other relevant stages.

17) Ensure all tables in the PDF are fully included to allow for a complete evaluation of the results.

18) Align the results with the research question (hypothesis) and objectives. For instance, results such as age characteristics do not fit the stated focus. Adjust the methods and introduction if the scope is broader than the stated patterns of reduction.

18.1) In particular state the rationale behind studying the age. It is not stated in the introduction, methods or discussion what it hast to do with patterns in the reduction of pediatric procedures or if it is a cofactor effecting reduction. The effect of age is not statistically addressed.

19) no infferential results are presented, aside from the statement in the methods section.

Discussion

19) Provide a cautious overall interpretation of the results and discuss their generalizability.

20) Address the effect of comparing one pre-COVID year to multiple post-COVID years.

21) Discussion evaluation is challenging due to missing results (e.g., incomplete tables).

22) Clarify the claim that "the strength of the present study is that it provides detailed data from a national perioperative database including almost all major Swedish hospitals with pediatric anesthesia." Provide evidence to support this claim and elaborate on what "almost all major" entails, as well as its implications for representativeness.

23) Discuss the study's limitations in more detail, particularly regarding the chosen methods. Consider potential sources of bias or imprecision, addressing both their direction and magnitude.

24) Please relate to other studys that study the impact of covid on admission and surgeries.

Overall

24) Reduce the number of figures in the appendix to only those that are directly relevant, I was overwhelmed

25) I cannot fully evaluate the manuscript, as not all data are included (tables do not fit the manuscript).

**********

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: No

Reviewer #2: Yes:  Jonas Bienzeisler

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[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.

Dear Dr. Melander,

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 Sep 14 2025 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.

• 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 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,

Andreas Vilhelmsson, Ph.D

Academic Editor

PLOS ONE

Journal Requirements:

1. If the reviewer comments include a recommendation to cite specific previously published works, please review and evaluate these publications to determine whether they are relevant and should be cited. There is no requirement to cite these works unless the editor has indicated otherwise. 

2. 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

Reviewer #3: All comments have been addressed

Reviewer #4: (No Response)

**********

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

Reviewer #3: Yes

Reviewer #4: Partly

**********

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

Reviewer #3: Yes

Reviewer #4: No

**********

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

The PLOS Data policy

Reviewer #3: Yes

Reviewer #4: Yes

**********

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

Reviewer #3: Yes

Reviewer #4: No

**********

Reviewer #3: The paper has addressed the issues previously raised and is now of sufficient quality for publication.

Reviewer #4: This manuscript investigates the changes in surgical volume in Sweden before and after the COVID-19 pandemic. The topic is of considerable interest, and the reported decrease in elective procedures aligns with many previous studies.

However, the submitted manuscript is very difficult to read and review. The authors use numerous unconventional abbreviations, particularly in the tables, and there is no clear distinction between the table legends and the main text, which severely hinders readability and interpretation.

In addition, the right margin of the manuscript is filled with unnecessary grey space created by Microsoft Word's comment function, which compresses the body text and makes it even more difficult to read. The manuscript also contains many typographical errors and nonstandard terminology, and it clearly should have undergone professional editing by a native English speaker before submission.

I strongly recommend that the authors revise the manuscript with greater consideration for reviewers, who are volunteering their time and effort. The manuscript should be written in a way that facilitates the review process.

Below are some specific questions and concerns regarding the manuscript:

Please specify the exact dates that define the "four different waves" of the pandemic. How were these definitions established?

In Table 1, please provide an explanation for the labels "19_20," "19_21," and "19_22." The legend states: "rate-ratio comparisons of the number of procedures during the different years, using a Poisson regression, adjusted for the Swedish population at risk during that specific year, using data from Statistics Sweden." However, it seems that these are simply the inverse of the proportion values. For example, the first entry (1.17 for 19_20) appears to be calculated by dividing 57099 by 49000, which corresponds to the inverse of 86% shown next to 49000. What is the actual basis for the reported p-values?

Does "EMB30" stand for "Distribution of waiting times for adenoidectomy"? Please clarify.

In the phrase "Forearm or elbow X. Closed reduction," what does "X" mean? This expression appears multiple times but is not standard terminology.

Does “extraction implant” mean “implant removal”? Please use established surgical terminology.

Does “Lap. excision” refer to laparoscopic excision? Please spell it out.

“Retentio testis” is a diagnosis, not a surgical procedure.

What is meant by "Diagnostic exam"? Please specify what kind of diagnostic procedure is being referred to.

Table 3 contains misaligned indentations and spacing, making it difficult to read. Please reconstruct the table for clarity.

"ENT" in "ENT/oral surgery" is not an internationally standardized abbreviation. Please provide the full term and its definition in both the abstract and the main text.

The Discussion section contains too many paragraphs. Some paragraphs consist of only one sentence, and others are divided without logical flow. This makes the text difficult to follow and does not adhere to standard academic writing conventions. Please restructure the Discussion for better coherence and readability.

The authors state that "The strength of the present study is that it provides detailed data from a national perioperative database including almost all major Swedish hospitals with pediatric anesthesia." However, this claim is not substantiated by the content of the manuscript. The level of detail in the data is not sufficient to be considered a particular strength.

In the Discussion, the phrase "nursing staff shortages in the wake of the pandemic" is used. Does this imply that there was a substantial reduction in the number of nurses in Sweden due to the pandemic? Please elaborate and provide references if possible.

**********

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 #3: No

Reviewer #4: 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

The Covid-19 pandemic in Sweden: prolonged and unevenly distributed effects on the volume of pediatric anesthesia and surgery demonstrated by data from the Swedish Perioperative Register

PONE-D-24-03764R3

Dear Dr. Melander,

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.

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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,

Andreas Vilhelmsson, Ph.D

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments: