Review for 10.1186/s12876-021-01987-z (2021)

Title: Can the Simplified Magnetic Resonance Index of Activity be Used to Evaluate
the Degree of Activity in Crohn's Disease?
Version: 1 Date: 09 Jun 2021
Reviewer's report:
Compliments to the authors: very nice article in which the diagnostic accuracy of the simplified
MaRIA score for disease activity in patients with Crohn's disease is evaluated by comparing the
MaRIAs with endocopisc results as gold standard.
There are several issues/questions that I hope the authors can address.
Introduction:
1. please provide a reference for your statement that in recent years there has been an increasing
incidence of crohn's disease and complications associated with CD.
2. please provide some insight and references as to why Crohn's disease has become an
increasingly complex digestive tract disease to diagnose and treat.
3. "MRI has good soft tissue resolution and is nonradioactive'. Might you possibly mean that
MRI does not use ionizing radiation? If yes, please rephrase.
Methods:
4. were the 107 patients consecutive patients?
5. with regard to description of MRI parameters: please consider using the terms slice thickness
and slice gap
6. table 2: you provide 3 columns for activity degree. The middle column includes all segments
with active disease; would it be possible to provide the subgroups of disease activity (as you
describe in the text) in the table? Were the 46 segments with severe ulcers indeed the only
segments that had a high SES-score? Did you use a cut-off value for the SES-CD to differentiate
between moderate and severe disease?
7. Table 3: please provide a caption/header for the columns; from the text I could infer that the
global SES-CD was compared with the biomarker, but I think it would be more clear for the
reader if you provided the info in the table as well.
8. table 4: I feel it would be very interesting to the reader if you could provide details about
the presence of the 4 MR variables across the different levels of disease activity. Right now in
active disease all 3 levels of active disease (mild, moderate and severe) are grouped.
Results:
9. "The global SES-CD was 14, ....and 18 for those with severe disease" Are the data provided in
this sentence correct? It seems strange that patients in remission would have such a high global
score? Also, why did patients with mild to moderate disease have a score of 61 and patients
with severe disease of 18?
10. please specify which groups were compared with regard to the significantly increased
incidence of fat straning and ulcerations in the group with severe disease. Also, I am not sure if
it is statistically sound to look at differences between three groups, when one of the groups is a
part of the other group (i.e. severe disease is a subgroup of active disease).
11. Table 7:
- With regard to the interrater agreement: although the kappa values are impressive to me, the
data in the table do not describe excellent agreement for all segments except the rectum: kappa
0.61-0.80 reflects substantial agreement.
- I do not completely understand why you would provide kappa values for the MaRIAs; this was
a consensus score if I have interpreted the text correctly?
Discussion:
12. You state that the interrater agreement show that the MaRIAs score is stable and repeatable. I
would suggest rephrasing this statement as the repeatibility of the score as such was not assessed
in this study.
13. Why would you consider the fact that radiologists were not blinded to Gd-enhanced
sequences a limitation, please explain?