Review for 10.1186/s12876-020-01296-x (2020)

Reviewer’ s report
Title: Elderly-onset vs adult-onset Ulcerative Colitis: a different natural history?
Version: 1Date: 28 Feb 2020
Reviewer: Petr Hruz
Reviewer's report:
To understand elderly-onset IBD is a very important topic in the field of IBD, therefore the
retrospective analysis of prospectively collected data as presented by the authors is important.Indeed the authors present different results which may be very interesting to better understand thecourse of disease in elderly patients.I have methodological issues with the data presented so farhere. At best, this a retrospective analysis of prospectively collected data. It seems to me that first94 patients with elderly onset were identified or selected (how many were not selected and why?)and then matched 1:1 to type of diseases, sex and year of diagnosis to patients between the age of40-64 years of age. I do not understand why not all patients were included that were diagnosedbetween 40-64 years of age. Why was a matching done, which seems to be something like a casecontrol. There is a substantial amount of patients that are excluded from the analysis with thisapproach. If the authors wish to do it this way it needs also to be reasonably explained why theywant to do a matched comparison and discuss the advantages and disadvantages of this approach. Ithink the methodological section needs a better description for the patient populations that arecompared. Also we need to know how many patients were lost to follow up and if available whythey were lost to follow up. I do not think that loss to follow up is an adequate exclusion criterium.
Are the methods appropriate and well described?
If not, please specify what is required in your comments to the authors.
NoDoes the work include the necessary controls?
If not, please specify which controls are required in your comments to the authors.
YesAre the conclusions drawn adequately supported by the data shown?
If not, please explain in your comments to the authors.
NoAre 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 furtherassessment 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:
Needs some language corrections before being publishedDeclaration of competing interests
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