Review for 10.1186/s12876-018-0928-2 (2019)

Reviewer ’s report  
 
Title:  Risk Factors and Long -term Outcome of Disease Extent Progression in Asian Patients 
with Ulcerative Colitis: A Retrospective Cohort Study  
 
Version: 1 Date: 30 Aug 2018 
 
Reviewer:  Jae Jun  Park 
 
Reviewer’s report:  
 
The aim of this study was to analyze the risk factors of proximal extension of ulcerative colitis 
and long  term outcomes. Authors found that only the baseline extent alone was a risk factor for 
proximal extension and patients with proximal extension more required therapeutic medication. 
This paper has been conducted on a relatively large number of subjects and  is well written and 
the results are systematically presented as a whole. However, it is a retrospective study, and it is 
a limitation of the paper that the findings are not novel compared to existing results.  
 
 
Several comments are as follows:  
 
1. In the a nalysis in Table 2, reference variable that is the basis of comparison is lacking. Specify 
which statistical method was used to perform the univariate analysis. Furthermore, there is only 
one variable in the multivariate analysis item. Was the multivariate  analysis performed based on 
only one variable?  
 
2. In the analysis of Table 3, specify the total number of patients for each group. Also, specify 
the detailed timing of analysis in this table.  
 
3. Specify which statistical method was used in Figure 3  
 
4. Specify for each analysis group for the first analysis in Figure 4. In Figure 4, specify the 
timing (from when the analysis was started) of the analysis in each group. Moreover, in 
statistical analysis section, further specify the statistical calculation m ethod in survival analysis 
regarding last follow up without event, sensoring methods etc.  
 
5. In general, E3 refers to the extent that is more proximal to the splenic flexure. Authors further 
classified E3 lesion based on hepatic flexure. Describe further in the discussion section whether 
this grouping has clinical significance (Consider quoting  a recent article from Dig Dis Sci. 2018 
Aug 25. doi: 10.1007/s10620 -018-5218 -x. ). 
 
Are the methods appropriate and well described?  
If not, please specify what is required in your comments to the authors.  
 
No 
 
Does the work include the necessary controls?  
If not, plea se specify which controls are required in your comments to the authors.  
 
No 
 
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:  
 
Not suitable for publication unless extensively edited  
 
Declaration of competing interests  
Please complete a declaration of competing interests, considering the following questions:  
 
1. Have you in the past five years received reimbursements, fees, funding, or salary from an 
organisation that may in any way gain or lose financially from the publication of this 
manuscript, either now or in the future?  
 
2. Do you hold any stocks or shares in an organisation that m ay in any way gain or lose 
financially from the publication of this manuscript, either now or in the future?  
 
3. Do you hold or are you currently applying for any patents relating to the content of the 
manuscript?  
 
4. Have you received reimbursements, fees, fund ing, or salary from an organization that 
holds or has applied for patents relating to the content of the manuscript?  
 
5. Do you have any other financial competing interests?  
 
6. Do you have any non -financial competing interests in relation to this paper?  
 
If you can answer no to all of the above, write 'I declare that I have no competing interests' 
below. If your reply is yes to any, please give details below.  
 
'I declare that I have no competing interests'  
I agree to the open peer review policy of the journa l. I understand that my name will be included 
on my report to the authors and, if the manuscript is accepted for publication, my named report 
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