Review for 10.1186/1471-230X-11-86 (2011)

Reviewer's report
Title:Appointment waiting times and education level influence the quality of
bowel preparation in adult patients undergoing colonoscopy
Version: 1Date:25 March 2011
Reviewer: Benjamin Lebwohl
Reviewer's report:
In this study, Chan and colleagues prospectively evaluated 501 patients who
underwent colonoscopy with the primary aim of identifying risk factors for poor
bowel preparation. The investigators also reported the impact of poor bowel
preparation on colonoscopy outcomes including cecal intubation rate,
colonoscopy time, and post-procedure discomfort. Risk factors for poor bowel
preparation included male gender, lower education level, non-adherence to
pre-procedure instruction, and a prolonged interval between scheduling and
performance of the colonoscopy. Poor bowel preparation was associated with
lower cecal intubation rate (regardless of operator experience), longer procedure
time, and increased post-procedure discomfort. Study strengths include its
prospective design, calculation of kappa statistics to support interobserver
agreement when rating preparation, and detailed measurements of important
procedure-related outcomes.
The authors point out in the Introduction that this area has been understudied in
Asia, though they do not mention a similar study in South Korea (Chung, et al J
Clin Gastro 2009) until the Discussion section. This reference should be moved
to the Introduction. Another limitation is the lack of data on the impact of poor
preparation on adenoma or polyp detection; given the extensive
procedure-related information collected during this prospective study, the
omission of these data is striking. Even if the study was underpowered to show
an association between preparation and adenoma prevalence, a univariate
analysis of this outcome would be welcome.
Major compulsory revisions:
How many endoscopists performed these colonoscopies? The section reporting
the kappa statistics mentions 3 endoscopists but do not see the number of
providers participating in the main study.
The preparation categories are a bit confusing. In the tables, the outcome is
dichotomized as "poor" vs. "non-poor." But in the methods section, the authors
suggest a trichotomized outcome, when they state that "they were re-categorized
for the purposes of subsequent of analysis as follows: good (i.e. excellent),
intermediate (combination of good & fair), and poor."
I am uncertain how to interpret the comparison of cecal intubation time among
senior endoscopists in table 3. The mean time is actually shorter (11.09 minutes)
among poorly prepared patients compared to non-poorly prepared patients
(11.12 minutes, p<0.001), though the authors suggest that poor preparation
lengthens cecal intubation time. Perhaps the discrepancy is a typographical
error, or it reflects a non-normally distributed set of times-- if this is the case,
perhaps this would be better shown as a box-plot graph.
Discretionary revisions:
The finding of increased post-procedure discomfort in those with poor
preparation is novel and intriguing, and should be further fleshed out. Was this
independent of the procedure time? Regardless of indication? (Perhaps patients
with an indication of abdominal pain were more likely to have a poor preparation
and more likely to have post-procedure pain.)
The authors should note that two variables traditionally thought to be associated
with poor preparation were not significant in this study: inpatient location and
later time of day. Perhaps later time of day was not significant because the
same-day administration of PEG in that group nullified their increased risk of poor
preparation.
Level of interest: An article of importance in its field
Quality of written English: Acceptable
Statistical review: No, the manuscript does not need to be seen by a
statistician.
Declaration of competing interests:
I declare that I have no competing interests