Review for 10.1186/s12876-023-03069-8 (2023)

Title: A PHASE 2 EVALUATION OF A NEW FLAVORED PEG AND SULFATE
SOLUTION FOR Colonoscopy
Version: 1 Date: 17 Oct 2023
Reviewer's report:
A PHASE 2 EVALUATION OF A NEW FLAVORED PEG AND SULFATE SOLUTION
COMPARED TO AN OVER-THE-COUNTER LAXATIVE, PEG AND SPORTS DRINK
BOWEL PREPARATION COMBINATION
Comments:
This paper describes an assessment of a new sports drink flavoured PEG-ELS for colon cleansing
prior to colonoscopy.
Comments:
1) Although presented as a comparative study, the authors need to clarify the time line of
recruitment. Were these groups evaluated in the same time period, or was one a historical cohort?
2) Did the study address a clearly focused issue?
Population, intervention and control were outlined. However, there was no clear mention
of primary and secondary outcomes. Safety in regard to electrolytes was mentioned in the
introduction with PEG-SD being an electrolyte unbalanced formulation, but it was not noted
what blood work, if any, would be done to assess for this in the study. Furthermore, no
assessment for symptoms was described in the methods but was alluded to in the results.
3) No mention of how patients were selected. No mention of which centers are involved.
20 participants were assigned to PEG-SD control group and 40 were “later” placed in the FPSS
group. There was a larger sample of FPSS participants and no randomization was used.
Figure 1 does not explain how 40 classified to FPSS group and 19 to PEG-SD.
There was mention that participants were demographically similar (gender, ethnicity and race),
however, no comorbidities were compared and age was not comparable within the groups.
PEG-SD participants were an average of 10 years younger than FPSS (PEGSD 49.7, FPSS 59.0)
There is no clear description of which centers participants were selected from, what the
demographic is like in those areas, and whether they were large or smaller centers. There was
also no description of why a larger proportion of participants were classified in the FPSS group
vs the PEG-SD group. Furthermore, with a 10-year average age difference, more >65-year-old
participants in the FPSS group and few POC in the PEG-SD group, the two groups may not
be completely comparable. With no mention of medical comorbidities within the two groups,
this creates further questions of how well the already imbalanced groups could compare to one
another.
This being said, with an older and more diverse population in the FPSS group, this could show
that the positive results are even more applicable to a larger population.
4) Questionnaire for satisfaction with prep: level of ease with consuming, experience rating,
comparison to previous, if would want to use again in future.
Only FPSS were asked about aftertaste and to what degree they believed it tasted better than
previous preps. There was no comparison for this as the PEG-SD group was not asked these
questions.
Subjects were not blinded to the exposure and nor was the outcome assessor - this could cause
bias in satisfaction results.
Study completed at various centers but not described how participants were collected from
centers and how many involved from each location.
A subjective 4-point scale different than the validated Boston prep scale or other validated scales
was used. Subjects and outcome assessors were both not blinded to exposure and can therefore
cause bias in perceived cleanliness and tolerability of prep. This may have been somewhat
mitigated by reviewers, but their credentials are not made available.
5) No confounders were identified in the paper.
Examples of possible confounders with colonoscopy prep include lifestyle (diet, habits,
additional water intake in this case) as well as health literacy.   With lack of confounding
variables identified there is risk of causal interference.
6) A major point mentioned in the introduction and study aim was safety, however, there is no
clear description of electrolyte testing or mention of how symptoms were assessed.  They did
mention that the symptoms experienced were consistent with expected bowel prep symptoms, 1
in each group had severe N/V. FPSS prep symptoms < 20% with 3 subjects vomiting (7%), 1 with
worsening bradyarrhythmia but no mention of frequency of symptoms in PEG-SD group as a
comparison. Serum chemistry parameters are mentioned to be small and not clinically significant
but not outlined in the paper. One FPSS experienced hypocalcemia and 1 PEG-SD participant
experienced hypernatremia.
7) As a phase 2 study it is interesting, but the cohort comparison, plus the attempted comparison
to results for other products in other papers does not help analysis.
8) In several places the results section has commentary better suited for the discussion section.