Review for 10.1186/s12876-021-01650-7 (2021)

Reviewer’s report
Title: 
High infliximab trough concentrations are associated with sustained
histologic remission in inflammatory bowel disease: a prospective cohort study
Version: 
1 
Date: 
21 Jan 2021
Reviewer's report:
while the authors have addressed most comments reasonable well further
revisions need to be made:
4. The median time between the 2 colonoscopies is 3 months. This is extremely
short. In my view way too short to call this sustained remission. Given a 3 month
follow-up between procedures this part is too weak to give meaningful insight. I
would suggest a meaningful definition of sustained remission is >6 ideally ≥12
months.
Response: We agree this is a limitation of our cohort. The following statement
has been added to the Discussion (page 15, ln 15):
" Additionally, colonoscopies were performed at different points relative to the
collection of blood for infliximab concentration quantification and the median
time
between colonoscopies was 3 months." 
Please add the following: A 3 month interval between colonoscopies may be to
short to assess for full interval changes in day to day clinical practice.
5. As there was no clear protocol for clinical care individual clinicians could
have altered dosing of IFX dependent on many factors including the initial
histology results.
This would introduce an amount of bias that makes sustained results
meaningless. Response: Thank you. This point is well taken. We agree that
physicians likely
adjusted dosing due to a variety of factors. However, a strength of this study is
the serial monitoring of infliximab concentrations over and up to 7 blood draws.
Providing
the mean infliximab concentration over time provides more information
regarding the blood concentrations required for remission than the evaluation of
a single blood
concentration as is typically done in most studies of infliximab exposure.
This requires a sentence in the discussion not only a response to my comment.
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