Review for 10.1186/s12876-015-0234-1 (2015)

Reviewer's report
Title:Cap assisted colonoscopy for the detection of serrated polyps
Version:3Date:24 August 2014
Reviewer: Thomas De Wijkerslooth
Reviewer's report:
This is a post-hoc analysis of the previous published randomized controlled trial
comparing adenoma detection with cap-assisted colonoscopy (CAC). Rastogi
and collegues now reported on serrated polyp detection by CAC. The hypothesis
of this paper is very relevant and it is adequately written. The authors lay stress
on the fact it is a post-hoc analysis, not powered for serrated polyp detection. I
have some major and minor comments which should be addressed first before
acceptance:
Major:
1. Title: Please change the title into: “Cap-assisted colonoscopy for the detection
of serrated polyps: a post-hoc analysis.”
2. Methods and Results: The authors describe the results of the per-protocol
analysis (after exclusion of subjects with inadequate bowel prep and/or failure of
cecal intubation). Please add the intention-to-treat analysis. I would suggest to
describe the results of the i.t.t. analysis in the text, and the results of the
per-protocol analysis in the tables.
3. Methods, definitions: Serrated polyps were defined as SSA/P, TSA, proximal
hyperplastic and large hyperplastic. Please explain why distal small hyperplastic
polyps were not included in the analyses. Probably they were not detected and/or
removed during colonoscopy as a consequence of the study design (post-hoc
analysis) and outcome measures (primary outcome: adenoma detection). Please
insert this as a limitation in the discussion section.
4. Methods, statistical analysis: In my opinion, the statistical analyses are
inadequate. The authors used Fisher’s exact test and Wilcoxon rank sum test.
Have the authors performed a preventative post-hoc control of the type I error
rate, such as Bonferroni or Fisher Least Significant Difference (LSD)? I would
advise a statistical review of a statistician.
5. Results: Please report the median or mean withdrawal/inspection time.
According to the original paper the withdrawal time was less than 6 minutes.
Please add this as a limitation in the discussion section.
6. Results: Please report the total number of study colonoscopies per
endoscopist and the serrated polyp detection rate per endoscopist. Please add to
the discussion section that the results were probably influenced by investigator
bias, because one endoscopist performed the majority of colonoscopies
(assuming comparable differences of the SP detection, as for adenoma
detection).
7. Discussion: Please shorten or remove paragraph 1, 2 and 3, it is a bit a
repetition of the introduction.
Minor:
8. Abstract (results) and Results: please report the median (skewed distribution)
or mean (normal distribution) serrated polyps per subject (including analysis of
this comparison), instead of the total number, as in the original paper.
9. Abstract, conclusion section: Please start the conclusion with: “In this post-hoc
analysis, CAC is a safe technique that offers a higher…..).
10. Methods: Have the endoscopist detected and removed all serrated polyps?
Probably not, especially not the distally located serrated polyps, as a
consequence of the study design and primary outcome. Please insert this as a
limitation in the discussion section.
11. Discussion: Please insert “strenghts of the study” to the discussion section
12. Discussion: Please add the above mentioned points to the “limitations of the
study”
13. It is mentioned that “the lack of statistical significance could very well be
explained by a Type II error, as the trial was not powered adequately to detect a
difference in these categories.” This is possible, however to my opinion, it is more
likely the significant results are the effect of a Type I error. Please see point 4.
Level of interest: An article of importance in its field
Quality of written English: Acceptable
Statistical review: Yes, but I do not feel adequately qualified to assess the
statistics.
Declaration of competing interests:
I declare that I have no competing interests.