Review for 10.1186/s12876-020-01534-2 (2020)

Reviewer’s report
Title: 
Narrow band imaging under less-air condition improves the visibility of
superficial esophageal squamous cell carcinoma
Version: 
0 
Date: 
22 Jun 2020
Reviewer: 
Ivan Kristo
Reviewer's report:
The submitted paper concentrates on a crucial topic, namely the early detection
of esophageal SCC. In this retrospective study the authors included a large
number of patients and compared video sequences in a retrospective manner and
detected superiority of low-air conditions when compared to standard
insufflation. The authors conclude that NBI under less air condition therefore
improves visibility of superficial SCC. However, some points still have to be
addressed 
1) Explain how the video review process was performed. Was there any protocol
followed? For example, which video sequences were reviewed first? Was there
any difference in the length of the recorded sequences? From my point of view,
this is crucial as long standard insufflation videos that explore the SCC region
may influence on reviewers as they are prepared for the lesion and impact the
subjective scoring of the SCC exploration in subsequent low-air videos. 
2) Were there any lesions undetected? 
3) The authors discuss that thickness of esophageal wall may impact on their
outcome. How do they explain that invasion depth was not a significant
prediction factor in univariate analysis?
4) The conclusion statements should be refined - we do not know if it really
improves visibility as the study has no prospective randomized and blinded
nature and uses no control patients - therefore the authors can only state that it
improved their subjective visibility. Moreover, only a subtype of SCC is
analyzed, therefore no general statement can be made about SCC in general (this
should be taken into account in the conclusion of the manuscript as well as in the
conclusion of the abstract)
5) A magnifying option was used under low air conditions - was it the same
under standard insufflation - this may also bias the outcomes and has to be
clarified
6) Was a multivariate analysis added for the significant factors that were
revealed under univariate conditions?
7) Who made the videos? Was there any significant difference in outcome
between investigating endoscopists?
8) In the background section 2nd and third line the numbers 3 and 4 appear
without context - please use past tense in the limitation section of the discussion
(were assessed by evaluators that...)
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Are the methods appropriate and well described?
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Yes
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authors.
No
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No
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require further assessment in your comments to the editors.
Not relevant to this manuscript
Quality of written English
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Acceptable
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