Review for 10.1186/s12876-020-01374-0 (2020)

Reviewer’ s report
Title: Fruit and vegetable consumption is associated with lower prevalence of asymptomatic
diverticulosis: a cross-sectional colonoscopy-based study
Version: 1Date: 16 Apr 2020
Reviewer's report:
PEER REVIEWER ASSESSMENTS:
OBJECTIVE - Full research articles: is there a clear objective that addresses a testable research
question(s) (brief or other article types: is there a clear objective)?Yes - there is a clear objective
DESIGN - Is the current approach (including controls and analysis protocols) appropriate for the
objective?No - there are major issues
EXECUTION - Are the experiments and analyses performed with technical rigor to allow
confidence in the results?No - there are major issues
STATISTICS - Is the use of statistics in the manuscript appropriate?
No - there are issues with the statistics in the study
INTERPRETATION - Is the current interpretation/discussion of the results reasonable and not
overstated?
Yes - the author's interpretation is reasonable
OVERALL MANUSCRIPT POTENTIAL - Is the current version of this work technically sound?
If not, can revisions be made to make the work technically sound?Maybe - with major revisions
PEER REVIEWER COMMENTS:GENERAL COMMENTS:
The authors conducted an observational study on the association of fruit and vegetable intake withprevalent diverticulosis. The authors observe an association of higher intake of f&v to beassociated with lower prevalence of diverticulosis. The paper clearly describes the procedures usedin the study. My main concern is about the used surveys to collect information on diet and physicalactivity, and about the use of logistic regression
REQUESTED REVISIONS:
One of my concerns is, that the authors did not use an existing validated questionnaire to collect
information on diet and physical activity. How well do these surveys capture diet and physical
activity? Are the validated in any way? How were they constructed and tested? I do not fully
understand the description in the methods. The authors write: "Specifically, we used theSemiquantitative Food Frequency Questionnaire(SFFQ) to define categories of dietary intake and aggregated individual foods into broader foodgroups (Supplementary Table 1)." However, they did not include a reference to thisSemiquantitative FFQ, so I do not know how that one differs from the one they used. How didthey decided to aggregate some of the foods into broader groups? How was this all validated? Thecorrelation between the SFFQ and the brief version is not really high, so what does this mean forthe validity of their findings? How well does the survey rank individuals of low or higher intake?
For physical activity, I have the same concerns. Authors did not use an existing survey. How
confident are they that they can actually rank participants well with regards to physical activity?Although physical activity was not the major focus of this paper, it may very well confound theassociation of diet and diverticulosis.
My other concern is about the odds ratios. An odds ratios overestimates the risk when the outcome
of interest is not rare. In this manuscript, the outcome of interest is certainly not rare. In such cases,it may be better to calculate Prevalence Ratios instead of Odd Ratios (see for example: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5135596/)ADDITIONAL REQUESTS/SUGGESTIONS:The authors drew their sample from the GIDER cohort. I don't know how big the full cohort is,and how many patients were excluded because they did have full data. The authors should includea description of the full cohort, relative to their sample (for example were excluded patients older,more often female, more comorbidities etc).
Are the methods appropriate and well described?
If not, please specify what is required in your comments to the authors.
No
Does the work include the necessary controls?
If not, please specify which controls are required in your comments to the authors.
NoAre the conclusions drawn adequately supported by the data shown?
If not, please explain in your comments to the authors.
YesAre you able to assess any statistics in the manuscript or would you recommend an
additional statistical review?If an additional statistical review is recommended, please specify what aspects require furtherassessment in your comments to the editors.
I am able to assess the statistics
Quality of written English
Please indicate the quality of language in the manuscript:
AcceptableDeclaration 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.
This reviewer has been recruited by a partner organization, Research Square. Reviewers with
declared or apparent competing interests are not utilized for these reviews. This reviewer hasagreed to publication of their comments online under a Creative Commons Attribution Licenseattributed to Research Square and was paid a small honorarium for completing the review within aspecified timeframe. Honoraria for reviews such as this are paid regardless of the reviewerrecommendation.
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