Review for 10.1186/s12876-021-01637-4 (2021)

Reviewer’s report
Title: 
Prevalence of biliary acid malabsorption in patients with chronic diarrhoea
of functional characteristics. A prospective study.
Version: 
0 
Date: 
01 Aug 2020
Reviewer's report:
This is a prospective study designed to assess the prevalence of BAD in a
selected group of patients with functionel diarrhoea.
The primary research question and methods is clear. The paper is well written. 
However, this research question has been evaluated earlier and the results
confirm what we already know and no much new data has been provided.
The secondary research question: "the response to Bile acid sequestrants" cannot
be answered properly by the methods used in this study as it is open-labbeled
treatment of only a few patients; however this question is much more interesting
as now data from RCT exists and more information on this part of the study is
needed:
1) Patients were advised to increase dose of BA sequestrants every second day
up to 12 g/day. That is results of efficacy was already present after 2 weeks, but
follow-up was after 20 weeks ? Howcome?
2) How was the medication advise provided to the patients; at inclusion orally or
written information ?
3) Did the patients keep diary about stool frequency and BA sequestrant dosages
? 
4) Which precautions were made to avoid recall bias ?
5) 10 patients did not have response or had side effects to BA sequestrants. The
median dose was 4,5 gram in this group, how many reached 12 g before not
having effect ? if patients stopped due to constipation as a side effects, did they
got help to reduce to a dose that could relieve their diarre 
without constipation ?
Inclusion/exclusion criteria:
was 
loperamide or bulging agents allowed ?
Discussion: different methods to detect BAD, you do not mention FGF - 19 ?
Results and Table 1: a normal CRP is part of inclusion/exclusion criteria.
Howcome the normal values are mentioned in the table, what did you expect to
find and what is the reason for examining CRP and fibriongen in this patient
group ?
Table 2: I suggest you include number of patents with side effects in this table
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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?
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