Review for 10.1186/s12876-017-0708-4 (2017)

Reviewer ’s report  
 
Title:  Adenocarcinoma Risk in Gastric Atrophy and Intestinal Metaplasia: a Systematic Review  
 
Version: 0 Date: 13 Aug 2017 
 
Reviewer:  Ana Ferro  
 
Reviewer’s report:  
 
Congratulations on successfully completi ng this systematic review. The topic is interesting and 
surely fills a gap in current knowledge regarding gastric cancer development.  
 
- According to the systematic review protocol, you were intended to include case -control 
studies. Why did you choose to f ocus only on cohort studies?  
 
- What was the protocol in terms of duplicate studies, meaning, evaluating the same cohort 
but reporting different follow -up times, for instance?  
 
- Please remove the mention of meta -analysis in the flowchart, since you did not do meta -
analysis; you did quantitative synthesis based on the description of the results present in 
the 15 studies.  
 
- The Newcastle -Ottawa Scale (NOS) has its advantages and limitations; however, some 
discussion has arisen around its true value in terms of  quality assessment of the studies 
included in systematic reviews. What was the reason for you to choose such scale? Also, 
the authors refer in the first paragraph of the discussion that the heterogeneity observed 
was due to poor quality of the studies, al though all studies had moderate to high quality, 
according to the NOS. Study characteristics, like sample choosing, length of follow -up, 
are often the main reason for heterogeneity; therefore, I need more clarification in how it 
is the poor quality of the studies the reason for heterogeneity.  
 
- For each subgroup analysis, you describe (in the results text) the range of incidence rate, 
except for the quality score, for which you only describe the amount of studies. It would 
benefit the coherence of the descr iption if the incidence rate range for quality scores 
would also be described.  
 
- High I² value was the reason given to not show the overall estimates obtained through 
meta -analyses, but your figures show the weight that every study had for that overall 
estimate. Since you do not show this estimate value, I think it would suit better your 
results to show the quality score of each study, instead of the specific weight.  
 
- Please provide the reference that supports this sentence: "A recognised limitation of 
systematic reviews includes the impact of demographic and study methodology 
variation."  
 
- Looking at the funnel plots. I believe that the one regarding IM might not present 
publication bias, although the one regarding GA leaves me with doubts. Taking into 
account the known limitations of the funnel plots, particularly with low number of 
studies, I think it would benefit the paper if the authors performed the Egger's test and 
present the result.  
 
- As you mention in the limitations' section of the discussion, " there were several studies 
that determined GC in a GA/IM cohort but did not report sufficient information for the 
incidence rate to be calculated". Do you consider re -analysing all studies in order to 
include other risk measures instead of incidence rates,  such as risk ratios or hazard ratios?  
 
Are the methods appropriate and well described?  
If not, please specify what is required in your comments to the authors.  
 
Yes 
 
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.  
 
Yes 
 
Are 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 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  
Please complete a declaration of competing interests, considering the following questions:  
 
1. Have you in  the past five years received reimbursements, fees, funding, or salary from an 
organisation that may in any way gain or lose financially from the publication of this 
manuscript, either now or in the future?  
 
2. Do you hold any stocks or shares in an organisation that may in any way gain or lose 
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?  
 
4. Have you received reimbur sements, fees, funding, or salary from an organization that 
holds or has applied for patents relating to the content of the manuscript?  
 
5. Do you have any other financial competing interests?  
 
6. Do you have any non -financial competing interests in relation to this paper?  
 
If you can answer no to all of the above, write 'I declare that I have no competing interests' 
below. If your reply is yes to any, please give details below.  
 
I declare that I have no competing interests.  
 
I agree to the open peer review policy  of the journal. I understand that my name will be included 
on my report to the authors and, if the manuscript is accepted for publication, my named report 
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to the editors, which will not be published . 
 
I agree to the open peer review policy of the journal