Review for 10.1186/s12876-021-01693-w (2021)

Reviewer’s report
Title: 
Gut microbiota composition and functional prediction in diarrhea-
predominant irritable bowel syndrome
Version: 
2 
Date: 
03 Aug 2020
Reviewer's report:
I applaud the authors on studying a challenging yet important are of
neurogastroenterology. Microbiome has remained a hot topic of interest in IBS
and yet despite years of interest, our understanding remains crude.
1. Was any sample size calculation performed? How was the decision made to
recruit 30 patients? Although sample size is similar to other published studies, I
fear the study is underpowered and this needs to be added in discussion as
limitation.
2. Antibiotics often have long lasting effect on microbiome and 2 weeks of
washout period may not be sufficient. Past antibiotic use may be a confounder
here. Please add this as limitation.
3. Please define organic heart disease. Why were these patients excluded?
4. 'psychopath' is not an appropriate medical term. Suggest describing or
defining what authors mean by this term and state if this indicates any
psychiatric comorbidity.
5. Obesity has an effect on microbiome. It seems both group's BMI were
significantly different, albeit by a small difference. Please discuss this as
potential confounder in limitations.
6. In discussion, recommend adding a paragraph of limitations discussing above
limitations, this should be prior to conclusions. Conclusions should summarize
one or two major points of the article.
7. Line 38: change to 'categorized into four subtypes'.
8. Figure 4: Legend is missing.
9. Line 225: Suggest, 'this study is the first to analyze'.
10. Line 270: Suggest 'China has undergone'.
11. Line 292, I don't think the present study can validly conclude that IBS-D
patients are characterized by 
a 'thin body'.
Publons Reviewer Recognition
. Springer Nature can send verification of this
review directly to Publons (a subsidiary of Clarivate Analytics). If you would
like to take advantage of this service, please click on the “Yes” option below.
Your name, email address, title of the reviewed manuscript, name of the journal,
and date of your review submission (the “Review Data”) will then be transmitted
to Publons after the final decision on the manuscript has been made. If you have
already registered at Publons, they will notify you of the receipt of this review
and update your profile 
as per your settings and their policy. If you are not
registered with Publons, you will receive an email from them asking you to
register in order for them to be able to recognize your review on your new
profile page. Publons may use the Review Data to generate derivative metadata
for the benefit of Publons and you as a reviewer, carefully considering the
sensitivity of such information. For example, Publons may verify your record as
a reviewer by updating your profile published on its webservice if you have
registered for such service or help editors to identify candidate reviewers. Please
find the details of processing in Publons’ privacy policy
https://publons.com/about/terms
Yes
Declaration of competing interests
Please complete a declaration of competing interests, considering the following
questions:
1
. 
Have you in the past five years received reimbursements, fees, funding, or
salary from an organisation that may in any way gain or lose financially
from the publication of this manuscript, either now or in the future?
2
. 
Do you hold any stocks or shares in an organisation that may in any way
gain or lose financially from the publication of this manuscript, either now
or in the future?
3
. 
Do you hold or are you currently applying for any patents relating to the
content of the manuscript?
4
. 
Have you received reimbursements, fees, funding, or salary from an
organization that holds or has applied for patents relating to the content of
the manuscript?
5
. 
Do you have any other financial competing interests?
6
. 
Do you have any non-financial competing interests in relation to this
paper?
If you can answer no to all of the above, write 'I declare that I have no competing
interests' below. If your reply is yes to any, please give details below.
'I declare that I have no competing interests'
Reviewer Publication Consent.
 I agree for my report to be made available
under an Open Access Creative Commons CC-BY License (
http://creativecommons.org/licenses/by/4.0
) if this manuscript is accepted for
publication. Any comments that I do not wish to be included in the published
report have been included as confidential comments to the editor, which will not
be published.
If you are not happy for us to publish this report, please contact the editorial
office before completing the review.
If you wish, you can include your name in your published report. Please note
you must decide whether to include your name at the start of the process and
confirm this decision whenever prompted. If you change your decision later, we
will not be able to publish your name.
I agree to the terms of the CC-BY 4.0 license; please 
do not
 publish my name
with my report. (default)
Is the study design appropriate to answer the research question (including the use
of appropriate controls), and are the conclusions supported by the evidence
presented?
Yes
Are the methods sufficiently described to allow the study to be repeated?
Yes
Is the use of statistics and treatment of uncertainties appropriate?
Yes
Is the presentation of the work clear?
Yes
Are the images in this manuscript (including electrophoretic gels and blots) free
from apparent manipulation?
Yes