Review for 10.1186/s12876-020-01336-6 (2020)

Reviewer ’s report  
 
Title: Short -course Rifaximin therapy efficacy and Lactulose H ydrogen Breath Test in Chinese  
patients with Diarrhea -Predominant Irritable Bowel Syndrome  
 
Version: 0 Date: 04 Apr 2020  
 
Reviewer: Carmelo Scarpignato  
 
Reviewer's report:  
 
This is a straightforward study, evaluation the effect of a short -term, low -dose effects of 
rifaximin in patients with D -IBS. 
 
Despite being merely confirmatory of the available data, this investigation presents some 
important drawbacks, outlined below:  
 
 
INTRODUCTION  
 
On line 43, "microbiological pathogenesis of IBS" should be "microbial pathogenesis of IBS"  
 
When mentioning the association between SIBO and IBS, the Authors quote the old meta -
analysis of Ford et al. (2009), but forget to mention two more r ecent ones [Shah et al., Dig Dis 
Sci 2010; 55: 2441 -2449; Chen et al., J Gastroenterol 2018; 53:807 -818], the last one including 
23 studies.  
 
Along the same lines, when quoting the single studies on rifaximin's efficacy in IBS, the meta -
analysis by Menees  et al. [Am J Gastroenterol 2012; 107: 28 -35], representing the top of 
evidence, should be quoted.  
 
 
STUDY DESIGN &amp;  PROCEDURES  
 
This is an open -label, not controlled study. Although the SIBO eradication is an objective 
measurement, symptom evaluation ( especially with the Likert scale) is rather subjective. 
Therefore, any result (and consequent conclusion) from this investigation should be taken with 
caution.  
 
Although given for 2 weeks, the rifaximin dose (400 mg daily) is rather low. As shown in the 
meta-analysis by Gatta &amp;  Scarpignato (2017) and by the study by Lauritano et al. [Am J 
Gastroenterol 2008; 103: 2031], the eradication of SIBO is clearly dose -dependent, with the 600 
mg daily for 7 days giving only 16.7% eradication rate.  
 
 
The lactulose breath test, selected to identify SIBO, is less specific and less sensitive than the 
glucose hydrogen breath test [Lo &amp;  Chan, Clin Gastroenterol Hepatol 2013; 11: 483 -490] 
and gives a higher proportion of SIBO -positive, IBS patients [Ghoshal, Gut &amp;  Liver 2017; 
11: 196 -208]. The latter should therefore be preferred.  
 
At the end of the first paragraph, "25 g of lactose" should be "25 g of lactulose".  
 
When interpreting hydrogen breath test results, the criteria recommended by the Rome 
Consensus [Gasba rrini et al. Aliment Pharmacol Ther 2009; 29 (Suppl 1): 1 -49] and the 
American College of Gastroenterology [Rezaie et al., [Am J Gastroenterol 2017; 112: 775 -784] 
should be followed.  
 
Since SIBO eradication rate by rifaximin is affected by concomitant use of treatments affecting 
gut microbiota, as reported by Gatta &amp;  Scarpignato [Ref#30], the patients' intake of fibers 
(prebiotics) and probiotics should be clearly quantitated and indicated.  
In any case, the Authors state that "a symptomatic evaluation a fter 2 weeks might show 
improvement BEFORE the LHBT normalizes". However, according to Figure 1, there was no 
evaluation BEFORE 2 weeks, when SIBO eradication was assessed. Therefore, how the above 
statement could be justified?  
 
According to the results re ported in the study, both patients with and without SIBO showed 
symptom relief (and consequent improvement of HRQL) after rifaximin treatment. This is not 
unexpected since rifaximin displays an intrinsic anti -inflammatory activity that can target the 
minim al inflammation underlying IBS [Enck, Azi, Barbara et al., Nat Rev Dis Primers 2016; 2: 
16014].  
 
What was the success rate amongst patients in whom SIBO was eradicated and what was the rate 
in those without SIBO? Was the difference statistically significant? These figures are mentioned 
(without 95% confidence limits) in the DISCUSSION and should be gi ven - together with a 
specified statistical analysis - in the RESULTS section.  
 
 
DISCUSSION  
 
The authors mention the meta -analysis of Shah et al. [Aliment Pharmacol Ther 2013; 38: 925 -
934], which only included 3 studies of which 2 were unable to highlight any signiﬁcant effect of 
antibiotic therapy [Scarpignato &amp;  Gatta, Aliment Pharmacol Ther 2013; 38: 1409 -1410].  
 
Comparing the success rate of the present investigation with that observed in the TARGET 1 and 
TARGET 2 trials is not appropriate. Indeed, t he TARGET population was unselected whereas 
patients studied here where sub -grouped in SIBO positive versus SIBO negative individuals.  
 
The Authors mention the Ghoshal's study [Indian J Gastroenterol 2018; 37: 416 -423] showing an 
acceleration of colonic tr ansit after rifaximin treatment. This (albeit indirect) effect could be 
useful in patients with C -IBS but certainly not in those with D -IBS. This finding is therefore 
NOT relevant to the results of the current investigation.  
While the limitations of the s tudy due to the experimental design are outlined well, the 
discussion of the potential mechanisms of rifaximin is rather poor. It does not mention the drug -
induced metabolomic changes [Bajaj et al., PLoS One 2013; 8: e60042] as well as the increase in 
the relative abundance of Faecalibacterium prausnitzi, a gut microorganism endowed with 
powerful anti -inflammatory activities [Ponziani et al., Benef Microbes 2020; Epub ahead of 
print].  
 
 
REFERENCES  
 
The Ref#33 is a duplicate of Ref#30.  
 
 
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 com ments to the authors.  
 
No 
 
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 r eview?  
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 man uscript:  
 
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 reimbursements, fees, funding, or salary from an organization that 
holds  or has applied f or 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 am member of the Speakers' Bureau and Scientific Board of ALFASIGMA, the manufacturer 
of rifxamin  
 
I agree to the open peer review policy of the journal. I understand that my name will be included  
on my report to the a uthors and, if the manuscript is accepted for publication, my named report  
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which I do not wish to be included in my named report can be included as confidential comments  
to the editors, which will not be published.  
 
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