Review for 10.1186/s12876-018-0924-6 (2019)

Reviewer’ s report
Title: Predictive Modeling of Disease Burden in Adult-Onset Ulcerative Colitis Using Health
Administrative Data
Version: 0Date: 25 Nov 2018
Reviewer: Glen Doherty
Reviewer's report:
The authors present a study of health administrative data from adults patients with newly
diagnosed UC from a single Canadian centre. The data were analysed with a view to creating amodel predictive of disease burden (either extensive and/or severe UC). The results are interestingbut even the best models performed only fairly in the discrimination of patients with high diseaseburden. The authors take what could be considered an excessively optimistic slant in theirconclusions, given that they do not present any validation data which is the single biggestweakness. Rather than suggesting (as they do in the conclusion of the abstract) that these modelscould be applied in future population based studies I think the conclusion should rather be thatthey need to be applied in other cohorts for validation. I'm concerned that in the records review ofthe Ottawa patient cohort it is not stated how many patients had a prospectively documentedendoscopic Mayo score. If the severity was retrospectively inferred in a high proportion this willundermine confidence in the model. The other big issue, which is touched on but not adequatelydiscussed, is the fact the disease burden of the cohort does not reflect that seen in population basedstudies (only 20% with proctitis, almost 50% with high disease burden); there is huge potential forbias arising and again this underlines the need for the model to undergo validation in arepresentative population based cohort before it can be applied more widely. A few other minor
issues; there are a number of errors where words are duplicated in the text (e.g. Page 5,
linkagelinkage, datadata). On page seven the authors describe that total disease burden is 'acombination of extent and activity' but there is no precise description of how the two metrics arecombined. On page 9, I find the definition of 'high disease burden' confusing; can I suggest forclarity listing each category that is included (e.g. moderate extensive, severe extensive and severeleft sided; correct?). Overall the manuscript is otherwise well written but I think the Discussioncould be shortened.
Are the methods appropriate and well described?
If not, please specify what is required in your comments to the authors.
YesDoes the work include the necessary controls?
If not, please specify which controls are required in your comments to the authors.
Unable to assess
Are the conclusions drawn adequately supported by the data shown?
If not, please explain in your comments to the authors.
YesAre 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 recommend additional statistical review
Quality of written English
Please indicate the quality of language in the manuscript:
AcceptableDeclaration of competing interests
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