Review for 10.1186/s12876-023-02796-2 (2023)

Title: Risk factors for inadequate bowel preparation before colonoscopy: a retrospective cohort
study
Version: 7 Date: 04 Feb 2023
Reviewer's report:
Abstract
Much better
You revised the methods section to better describe the prep, I would do the same for the abstract.
"They were instructed to drink half of the volume the night before colonoscopy, and the other
half was given in divided doses of 250 ml every 10 minutes 4-6 hours before the procedure. All
patients received 30 ml of simethicone 4-6 hours before colonoscopy. "
Suggest:
They were instructed to drink 1.5 l the night before the colonoscopy and 1.5 l  4-6 hours before
the procedure given in doses of 250 ml every 10 minutes with 30 ml of simethicone given 4-6
hours before the colonoscopy.
INTRODUCTION
Much better
M+M
"Sufficient bowel preparation was defined as BBPS # 6 with each segment # 2 [15], the rating is
after cleaning maneuvers are performed. "should be removed. Your previous sentence says that.
"The points are assigned as follows" add "after cleaning maneuvers are performed".
This is the third time I bring up this point since it is important:
15. My questions from last time> Was season the primary endpoint of the study when it was
designed?
Your Response 1: Thank you for your helpful comment. As you said, we found that
season may be an influencing factor of poor intestinal preparation through clinical
observation, so we took season as one of the variables in our data statistics
My Question: The study endpoints are really your multi-variable analysis of risk factors for
inadequate preparations as defined by BBPS segments all >=2. I think you need to list the
variables you planned to analyze when the study was
designed and if that included season. Was season something you added after you had the data
and noted it was statistically significant?
Most studies describe a primary endpoint and secondary endpoints before the study is
undertaken. For example, if you have 20 endpoints you evaluate, then, just by chance alone, one
is likely to be positive at a 0.05 level. It needs to be clearly stated in the design of the study
what the
Response 2: Thank you for your careful advice. During the design phase of our study, the initial
consideration was to find that many patients underwent colonoscopy had inadequate bowel
preparation quality even after taking intestinal cleansers as required. Therefore, our primary
endpoint in designing this study was to explore risk factors for
inadequate bowel preparation quality, and season was included as only one factor that
might affect bowel preparation quality. In addition, patients' basic information (age, sex), chief
complaint, time for colonoscopy, colonoscopic findings and hospitalization status were also
included as potential factors.
For a study like this, your methods section clearly needs to state what variables were analyzed
using your univariate analysis . Were these variables identified to be analyzed before the study
was begun as part of the initial study design?  Were any added later after you had your data?
Discussion
"Third, since we selected polyethylene glycol electrolyte (PGE) powder (#) and silicone oil for
bowel preparation"
You mean "simethicone" not "silicone oil"
Table 1
Male gender
Age (mean ± SD) SD needs to go to the 0.1 place (one more significant digit).
Table 2
Needs to include "adequate bowel preparations were defined as all 3 segment scores 2 or 3".
Table 3
Nicely done.
Table 4
I believe you mean "Male Gender"
Spring should be Spring Season (same for the other 3).
Timne for colonoscopy should be "Mornign colonoscopy" or "Afternoon colonoscopy"
Overall, you have made major improvements.