Review for 10.1186/s12876-021-01781-x (2021)

Reviewer’s report
Title: 
Hospitalization and surgery rates in patients with inflammatory bowel
disease in Brazil: a time-trend analysis
Version: 
0 
Date: 
25 Feb 2021
Reviewer's report:
This study describes temporal evolution (since 2005 to 2015) of IBD-related
hospitalization, surgery and mortality rates in the Brazilian population. An
anonymous national database including information from the health system was
interrogated. Results show a reduction of all considered variables over time,
being in line with other previous published similar analyses. The main strengths
of this study are the population setting (Brazilian) and the description of data in
different (rural or metropolitan) geografic area, although the latter point is barely
applicable to other countries. 
There are some important issues that should be resolved. 
Major concerns: 
- the criteria of the study period selection (2005 - 2015) are not clear. The
sentence (Page 7 line 8) "the period of study was selected based on the most
recent and standardized data available" is not enough exhaustive. Do you mean
than before 2005 the data in the registry were not complete or recorded in a
different way? And what about years 2016-2020? Please specify. 
- a different statistic software was used (SPSS for some analyses and Microsoft
excel for others, such as linear regression). Why? Please, specify. It would be
better to get consistent data using the same software for all analyses. 
- how do you explain the higher surgery rates in young patients (20 to 39 ys)?
The IBD prevalence is not taken into account in any of the analyses. May these
surgery rates be correlated with a higher prevalence of the disease among those
patients? Please, clarify. 
- the in-hospital lethality (19.8% in 2005 and 10.6% in 2015) reported in this
study seems to be higher than that reported in other European or USA studies
(just an example: Guasch et al. DLD 2021: in-hospital mortality around 2.5% in
CD and 6% in UC). In the discussion (page 15), a comparison with other
reported mortality data should be added, and possible reasons of different
findings should be hypothesized. 
Minor remarks: 
- what do you mean with "enterectomy"? Ileocolonic resection?
- page 14, line 23: the authors mention a "reduction in the number of available
beds", which is not described at any part of the paper. Is it referred to
gastroenterology units or to the general health system setting?
- Page 15, line 6: "abdominal abscess" into brackets is not a type of surgery but
an indication to surgery. Please, modify as appropriate. 
- If you start using abbreviations (i.e. "MR"), please use it in the entire paper,
just to be coherent.
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Is the study design appropriate to answer the research question (including the use
of appropriate controls), and are the conclusions supported by the evidence
presented?
Yes
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No
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from apparent manipulation?
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