Review for 10.1186/s12876-020-1170-2 (2020)

Reviewer’s report
Title:  Superiority of mucosal incision-assisted biopsy over ultrasound-guided fine needle aspiration
biopsy to diagnose small gastric subepithelial lesions:A propencity score matching analysis
Version: 0 Date: 21 Aug 2019
Reviewer: Werner Dolak
Reviewer's report:
This  is  a  comprehensive  study  that  describes  a  useful  diagnostic  method.  I  have  the  following
comments:
1) You report on the location of subepithelial lesions (upper, middle, lower part of the stomach) - did
you also record the gross appearance / growth pattern of the lesions? Any knife-assisted technique
might work well in such types of lesions that protrude into the gastric lumen but might become difficult
as soon as the majority of the lesion is inside the wall or even outside of the organ. 
2) Was there a difference in diagnostic yield between the different needles used for EUS guided tissue
sampling? It is quite likely that dedicated FNB needles like Acquire will perform better than FNA
needles like Expect, for example.
3) When describing tissue handling in the methods section you say "Procedures were repeated a
maximum of six times until samples containing spindle cells were obtained, which indicated that the
needle had penetrated the
SEL.  Those  multiple  attempts  were  performed  without  waiting  for  the  on-site  evaluations  by
pathologists, to minimize the procedural time." To me, this not clear. Did you wait for spindle cells but
not for the final diagnosis?
4) The majority of lesions in this study are GISTs. According to most guidelines these lesions would be
referred for surgery directly if the lesion size exceeds 2cm. What was the indication to take a biopsy in
the bigger size group then? Where these all metastatic cases? Is that institutional practice? 
5) You compared procedural times. Did you also consider that even in knife-assisted biopsy sampling
EUS needs to be performed before starting the biopsy process? 
6) In your discussion, I miss the comparison to other diagnostic methods to obtain histological samples
in SETs (subepithelial tumors, which is a more common term than SELs by the way): single incision
needle knife (SINK) biopsy,  endoscopic unroofing, ESD itself, full thickness  resection, tunneling
techniques. 
Are the methods appropriate and well described?
If not, please specify what is required in your comments to the authors.
Yes
Does the work include the necessary controls?
If not, please specify which controls are required in your comments to the authors.
Yes
Are the conclusions drawn adequately supported by the data shown?
If not, please explain in your comments to the authors.
Yes
Are you able to assess any statistics in the manuscript or would you recommend an additional
statistical review?
If  an  additional  statistical  review  is  recommended,  please  specify  what  aspects  require  further
assessment in your comments to the editors.
I am able to assess the statistics
Quality of written English
Please indicate the quality of language in the manuscript:
Acceptable
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