Review for 10.1186/s12876-021-01817-2 (2021)

Title: A Multicenter, Prospective, Inpatient Feasibility Study to Evaluate the Use of an Intra-
Colonoscopy Cleansing Device to Optimize Colon Preparation in Hospitalized Patients - The
REDUCE Study
Version: 2 Date: 12 Mar 2021
Reviewer's report:
This study evaluates a new device designed to complete colon preparation in patients
inadequately cleansed for colonoscopy. Inadequate colon preparation is an important and
common problem which increases the overall cost, and reduces the efficacy, of colonoscopy. In-
patients in particular have high inadequacy rates, thus presenting an excellent milieu in which to
test this device. Though this is a pilot study, all the findings, including potential downsides and
risks, should be presented in a balanced manner and included in the abstract where appropriate.
A more thorough discussion of the limitations related to study design is strongly recommended.
This, and other limitations of this study, should temper the findings and conclusions expressed
in this manuscript.
Major issues
• While the high adequacy rate in this study far exceeds that expected, this study is neither
blinded nor randomized. It is unknown how many patients may have had adequate cleansing
with standard measures alone and there is likely unconscious bias when reporting pre- and post-
Boston scores.
o With all patients being treated with the device, bias toward demonstrating efficacy could lead
to “deflated” pre-device scores and “inflated” post-device scores accounting for a component of
the significant difference observed. Please address this in both the discussion and abstract.
o Please present the pre- and post- BBPSs for the colon segments that could not be completed
with the device but eventually were seen with standard colonoscopy. If the pre- scores are not
available, then provide post. Also, provide whether these colon preps were overall adequate
upon completion using standard colonoscopy without the device. This may provide insight into
what was possible with standard cleansing measures alone.
• The same shortfall affects the data regarding the Kakugawa scale and predicting adequacy so
please address.
• The BBPS is designed and validated for grading after flushing and suctioning is complete. The
nonstandard application here before any cleansing should be discussed.
• Colonoscopy completion data should be presented for all patients (71/94, 76%), not just the
83. Even if the “intent to complete” group is included as a secondary measure, a high number
were incomplete largely or solely related to the device. This rate of incomplete colonoscopy is
much higher than standard and needs to be presented and addressed as a limitation of the device.
If endoscopist experience or other factors played a role, please describe.
• Colon perforation is a rare complication of colonoscopy, occurring generally less than 1/2000
or so procedures. This pilot of less than 100 cases has a perforation and should not be downplayed
and attributed to anything other than the device unless there is strongly compelling information
not presented. Please provide more details and address this in the manuscript.
• The definition of “successful colonoscopy” is not standard or intuitive. For a device that cleans
the colon, I would have thought success would defined as an adequately cleansed colon (along
with colon completion).  Was this definition used a priori in the protocol before starting this
study as an agreed upon outcome?
o Please do not use this in the abstract, which may be the only part that is read, as many
will incorrectly interpret this to mean that the device leads to a complete, adequately cleansed
colonoscopy in essentially all cases.
o Having done many inpatient colonoscopies where a definitive diagnosis is not made, it is
remarkable that such a high % of patients in this study had a diagnosis made during the
colonoscopy. Please provide information on these diagnoses.
• In cases where the source of bleeding was thought to be found distal to the cecum, was the a
priori design to stop the colonoscopy? I am not familiar with this approach of not completing
the colonoscopy other than specific circumstances such as added risk (such as patients having
severe colitis [exclusion criteria here]), obstruction, post-polypectomy bleed, or other unusual
circumstances. Please provide more detail on why these cases were not completed. The device
was not responsible for incomplete colonoscopy in any of these cases?
• The use of the visual scale to predict inadequate cleansing was a secondary, seemingly post
hoc, outcome. If so, why present this first in the title or even mention in the title?
• Please describe how monitoring for adverse events was performed. Three non-related mild
adverse events in almost 100 pts seems extraordinarily low and thus raises the question of
whether an assessment for adverse events was performed? Was air or CO2 used? If air, not a
single patient after longer than usual colonoscopy due to the device had abdominal discomfort?
Did any adverse events occur that patients may not have recognized such as colon trauma related
to the device?
Minor
• Did Fellows assist?
• Who assessed the BBPS?
• Please provide details of endoscopist experience with this device prior to this study, and the
relationship to incomplete procedures (and the perforation).
• In what % of subjects was the pediatric/slim scope used? If nearly all, this is important for
the reader to know.
• Any more details on prep?
o Everyone got 4 L PEG-ELS? Split? Timed to colonoscopy and if so what was the interval
used? Unless the prep timing was coordinated with the procedure, where the procedures AM/
PM/both? Any standard diet?
• While the device was on all the scopes, was there an assessment of whether it was actually
used and to what degree? Standard flush and suction remains available to the endoscopist with
the device loaded.
• Might be helpful to show an image of the clarity scale in the methods section
• Table 1
o Prefer age not be expressed as a fraction
o Indications – please provide the top 4 or 5 indications and then “other” and describe below
the table what is “other” and numbers per indication. Why is suspected neoplasia grouped with
transplant, and abnormal imaging with abd pain/diarrhea/weight loss?