Diagnostic Performance of Individual Symptoms to Predict SARS-CoV-2 RT-PCR Positivity and Symptom Persistence among Suspects Presenting in Primary Care during the First Wave of COVID-19

Round 1

Reviewer 1 Report

Thank you for the opportunity to revise this manuscript. This study is about the diagnostic performance of patients’ symptoms and description of the clinical course of patients with a positive compared to a negative PCR.

 

However, I have some suggestions:

 

Introduction

Almost all your references except refs 9, 10 and 16 are outdated (I think 2020 for COVID studies is outdated). I would recommend emphasizing on recent literature.

Lines 76-78 (However, few of these studies compared the duration of symptoms to patients without SARS-CoV-2 infection) – I am not sure it is accurate. Most recent literature about long-COVID does compare test-negative and test-positive patients.

Methods

In general, this method is too long and sometimes not concise enough. I have a few suggestions:

Please add the subheading “study design” and “setting” (together or apart, as suggested in the STROBE checklist). It will facilitate the navigation in the methods section.

Lines 131-132 : the sentence that begins with “Data for this study were… consent.” This was already described before. I would consider deleting this in order to avoid repetitions.

Lines: 142-143: the sentence that begins with “a specific symptom … not ticked”. I would consider deleting this sentence, it does not add up to the understanding of the study.

Lines 152-153: the sentence that begins with “partial or complete loss… respectively”. I would consider deleting this. I believe this is common knowledge to the readers.

Statistical analysis – this part of the methods needs major revision. Most of the statistical analysis focuses on your secondary objectives. I think most of this part should focus on the 2 main objectives and to a lesser extent the explanation about the secondary objective. I would consider moving some of this to the supplementary material (where you describe the detailed statistical methods).

Lines 208-212 – to me, this is counterintuitive. If possible, I would recommend doing it the other way around.

 

Results

Please add subheadings: participants in the beginning of this section (as suggested in the STROBE checklist).

In lines, 227-229 you wrote that 41% were health workers, however 43% had low education level and 75% had medium occupation level. How does it make sense? Please clarify.

Table 2 – please consider moving it to the supplementary material.

Figure 2 – is not clear and I am not sure it adds to the understanding of your data. Maybe try to make it easier to read.

Lines 284-288: you wrote that the median time to symptom recovery was 38 days among test-positive and 15 days among test negative. Later you wrote that certain symptoms lasted longer, but the median duration was shorter… (17 and 15 days respectively).

 

Discussion

Please add the subheading “main findings”   (as suggested in the STROBE checklist). In this section you should focus on the main results of your study and focus on your main objectives.

I think the discussion mostly addresses the secondary objectives and not the primary objectives. I think this should be revised.

The conclusion should first address the main objectives of this study.

 

 

 

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

This manuscript is well-structured, sound and useful information about COVID-19 during the first wave.

Major concerns.

1. How many Ct values that considered RT-PCR positive? Because some country uses Ct<37, but other use Ct <40.

Suggest clarifying the criteria of RT-PCR to the Methods.

2. Suggest adding the total confirmed cases and fatal cases during the first wave in Switzerland to the Introduction to make it more informative.

If possible, suggest adding the total population in the Canton of Vaud with confirmed cases and fatal cases.

 

Comments.

1. What is the targeting gene(s) for RT-PCR?

Are both RdRp and N genes or only used N gene?

2. That is interesting to add the variant circulated during the first wave. You can cite the publication, GISAIDS or Pangolin databases.

Nowadays, we know that almost the first wave was S clade. However, in the future, many readers will not understand what is the difference between waves.

Author Response

Please see the attachment (same attachment).

Author Response File: Author Response.pdf