Review for 10.1186/s12876-023-02649-y (2023)

Title: Evaluation of gut microbiota of Iranian patients with celiac disease, non-celiac wheat
sensitivity, and irritable bowel syndrome: are there any similarities?
Version: 1 Date: 19 Aug 2022
Reviewer's report:
Dear Authors, I have read this manuscript with interest and I would raise some points which
could be improved.
GENERAL COMMENTS
The main limit of this study lays in the extremely low number of patients recruited which
makes not possible to extend the results to the whole populations suffering of the three diseases.
However, this is the first study comparing three different conditions which are similar from
the clinical point-of-view, and, at least in part, seems to share some pathophysiological traits.
Overall, the research is adequately structured and elicited considering both study design and
analysis of the results obtained. The linguistic properties and the ways in which the different
sections are described demonstrate a thorough knowledge of the subject.
Some specific comments should be considered:
Background: the information contained in this section correctly and briefly introduces the topic
of the paper, providing adequate cues to the data reported in the following sections. Aims of
the study are clear.
Q1: in lines 73-74 authors states: ‘The thin line between CD, NCGS, and IBS is not always
clearly distinguishable, making it difficult to differentiate among them precisely [30-32]’. We
understand the aims of the authors in reporting this sentence, but it might be misunderstood. The
three clinical conditions, even if shares several clinical and some pathophysiological features,
are clearly differentiable one from the others. There are several guidelines and consensus which
elucidate the differential diagnosis among them. More specifically, CD has some autoimmune
and histological features which are well known and clearly differentiate it from NCGS and IBS.
I would suggest to eliminate these lines
Materials and Methods: the study design appears to be proportionate to the aims declared by the
authors. CD, NCGS and IBS diagnoses follow the current guidelines.
Q2: the authors reported the approval of the Ethic Committee. Was the study preliminary
registered in any international database (eg. clinicaltrials.gov, EudraCT, Japan Primary
Registries Network, etc)? If yes, can the authors provide the registration number? If no, can the
authors provide any explanation?
Q3: the authors do not clearly indicate the type of study. I think it is a monocentric prospective
observational study. Please, can the authors confirm and add it in the main text?
Q4: in lines 101-102 authors report that: ‘After physical examination and undergoing endo/
colonoscopy, patients with anatomical GI diseases were excluded from the study’. Do the
authors exclude also subjects suffering from systemic inflammatory diseases (i.e. autoimmune
conditions) ? It is known that such conditions could modify intestinal microbiota.
Q5: inclusion and exclusion criteria are not so clear; in lines 120-129 are reported some exclusion
criteria but they seem to be focused only on healthy controls. Can the authors add a bulleted list
that clearly indicates the inclusion and exclusion criteria for all the study groups?
Q6: in lines 105-109 authors report CD diagnostic criteria. In my opinion, as done for IBS and
NCGS, authors should refer to the current guidelines (“four-out-of-five rule”), which are a bit
different from the criteria reported by authors. Do the authors follow the “four-out-of-five rule”?
Results: data reported fit with the aims of the study. The tables and the figures allow a synthetic
and immediate understanding, even if some revisions are required.
Q7: in lines 175-180 authors describe the populations belonging to the 4 groups (IBS, CD, NCGS
and HC): ‘Due to age-related changes in the gut microbiota, the study groups were adjusted
according to their age so as not to have significant differences between them’. I agree with this
point but neither in the text nor in table 1 is reporting any statistic showing the lack of other
differences.
Q8: do the authors assessed the alimentary habits of the subjects? Was there any difference
among them? This is a focal point because the alimentary habits can consistently modify gut
microbiota. Please, admit this limit, if they did not look for it.
Q9: the authors do not report clinical features of these patients, which might be related to their
microbiota. Some authors, as example, report differences in microbiota composition according
to IBS subtypes, whereas other authors do not. It is possible to hypothesize that NCGS patients
which had only or mainly extraintestinal symptoms could have a different microbiota compared
to intestinal symptoms prevalent NCGS patients. I think that this analysis could be of some
interest improving the quality of the paper.
Q10: table 2 and figure 1 report the distribution of taxonomical groups in each group of the study
participants. I think that they should be modified to better explain the results reported in the text.
Table 2 should be modified adding the significance of intergroup differences.
Q11: in lines 183-184 authors reports: ‘The relative abundance analysis indicated that Firmicutes
was the most abundant bacterial group and the predominant phylum in all the studied groups
(46.2±14.0%)’. However, checking table 2 this is the value for CD patient.
Discussion: the analysis conducted on the results appears pertinent and complete. The reported
literature is adequate, supporting the authors' statements and giving authority to the data reported
by the study.
The weaknesses of the study were correctly framed and analyzed; however, the lack of a follow-
up and a comparison after a GFD should be accounted among the main flaws. Furthermore, we
think that the monocentric nature of the study, in a limited population with specific features could
be another main weakness of this study. Finally, if not enquired, alimentary habits assessment’s
lack is another flaw which must be addressed.