Review for 10.1186/s12876-021-01898-z (2021)

Reviewer’s report
Title: 
Utility of the Narrow-band imaging International Colorectal
Endoscopic classification for optical diagnosis of colorectal polyp histology in
clinical practice: a retrospective study
Version: 
0 
Date: 
20 Apr 2021
Reviewer's report:
The authors evaluated the utility of the NICE classification for endoscopic
diagnosis of colorectal polyps, and concluded that it has high sensitivity,
specificity, NPV, PPV and accuracy irrespective of the user (expert versus non-
expert). The study raises few questions that need to be fully resolved:
1. The study appeared to have been performed in 2013 (based on the study group
and IRB approval with an apparent date of 2013). The authors need to clarify if
this is true and the logic for studying cases diagnosed essentially in a dated era
compared to more recent cases. Not that this is critical but interpreting a set of
data from 2013 against more recent publications on the same topic with recent
data set needs to be put in perspective for the reader.
2. This study was silent about the results of prior validation studies for NICE and
in the introduction, the stated aim would suggest that was the first time anyone
was doing this, which isn't true. 
Therefore an acknowledgement of current
knowledge of strengths and and controversies of NICE need to be included in
the introduction, and the aim re-stated in this context to justify a need for this
study.
3. The findings of diagnostic accuracy of greater than 97.7-99.6% is significantly
better than in other recent studies (e.g overall accuracy of 76.7% in Patrun J, et
al. Gastroenterol Res Pract. 2018;2018:7531368). A discussion of the differences
in this and other studies will much lower accuracy is missing and needs to be
included.
4. A major issue over the years with NICE is in recognizing sessile serrated
polyps (SSP). This study however seems to have very few type 1 lesions and
silent completely about the representation of this difficult lesion in this study,
regarding NICE and SSP. The study conclusion cannot be deemed valid without
addressing hitherto identified difficult areas of performance for NICE.
5. In this study 92.0% of all polyps were neoplastic, presumably types 2 and 3.
This is rather high given the high prevalence of hyperplastic polyps in most
practices. Is this distribution characteristic of the authors' practice or were there
some other reasons why type 1 lesions accounted for only 8%, maybe some
selection factors?
6. The basis for selecting the 50 images for inter- and intra- observer study is
undefined, given there were 534 colorectal lesions with image sources.
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Is the study design appropriate to answer the research question (including the use
of appropriate controls), and are the conclusions supported by the evidence
presented?
Yes
Are the methods sufficiently described to allow the study to be repeated?
No
Is the use of statistics and treatment of uncertainties appropriate?
Yes
Is the presentation of the work clear?
No
Are the images in this manuscript (including electrophoretic gels and blots) free
from apparent manipulation?
Yes