Review for 10.1186/s12876-017-0578-9 (2017)

Reviewer ’s report  
 
Title: Prevalence of Paediatric Inflammatory Bowel Disease in Sweden: a Nationwide 
Population -Based Register Study  
 
Version: 0 Date: 22 Jun 2016  
 
Reviewer: Jennifer Debruyn  
 
Reviewer's report:  
 
Major comments:  
 I recomm end evaluation of the terms "cumulative prevalence" and "lifetime risk". Prevalence 
does not need to be defined as cumulative as one includes the period of time under study 
when describing prevalence. Cumulative prevalence is not the same as lifetime risk (i.e.  
cumulative incidence). Lifetime risk is also known as cumulative incidence when the period 
of time considered is an entire lifetime; cumulative incidence is the measure of the number of 
people who develop the disease during a period of time. Also, w hen calculating prevalence, 
the denominator should be all Swedish population <18 years of age between 1993 -2010. It 
should not be only the children <18 years on December 31, 2010. This may account for the 
difference of high prevalence in this study compare d to prior Swedish studies.  
o Page 4, lines 81 -82 
o Page 5, lines 90 -100 
o Page 9, lines 159 -165 
o Figure 1a, 1b  
o Page 11, lines 210 -212 
 Is the Registry a voluntary enrolment or are all patients automatically registered into it? Is it 
comprehensive?  
 Table 2: Recommend add superscript into table according to legend for definitions for terms. 
The percentages are confusing. If the row indicates 1993 -2010 or 2005 -2010, then the 
denominator used to determine the percentage should be the denominator of chi ldren with 
IBD during those time periods. For the top row, are these numbers for 2010 only (it is not 
clear)? Perhaps, the denominators for each time period should be in the legend below with a 
superscript to denote which denominator was used.  This should  also addressed on Page 10 to 
ensure the appropriate denominator is used to determine percentage.  
 For the immunosuppressant category, what is the breakdown for azathioprine, methotrexate, 
infliximab, and adalimumab? This would be of interest for the dis tribution of 
immunosuppressant use.  
 
Minor comments:  
 Recommend English edit for grammar corrections.  
 Define acronyms -NPR, ATC.  
 Use consistent number of decimal places in manuscript.  
 Reference for El -Matary is incorrect on Page 3.  
 When reporting prev alence, including % with the number is confusing. Using only the 
number per 100,000 is more easily comprehended.  
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, please specify which controls are required in your comments to the authors.  
 
Yes 
 
Are the conclusions drawn adequately supported by the data shown?  
If not, please explain in your comments to the authors.  
 
No 
 
Are you able to assess any statistics in th e 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:  
 
Needs some language corrections before being published  
 
 
Declaration of competing interests  
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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?  
 
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holds  or has applied for patents relating to the content of the manuscript?  
 
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6. Do you have any non -financial competing interests in relation to this paper?  
 
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