Review for 10.1186/s12876-020-01478-7 (2020)

Reviewer’ s report
Title: Classification of Gastrointestinal Symptom Patterns in Young Adults
Version: 1Date: 09 Apr 2020
Reviewer: Payman Adibi
Reviewer's report:
It is an interesting paper describing an endeavor:
a- define clusters of people within young population based on PROMIS-GI variablesb- to find correlation of these clusters with psychological covariates
There are some considerations that were not clearly done or described by the authors :
1- Inclusion : the authors may agree that they included the whole population i.e. both symptomaticand symptomatic cases ; although it was shown that about the model defined three clusters(Normal-Mild-Moderate) but it was more logical to run the calculations again with exclusion ofNormal cluster to make better models.Even it may be tried to exclude normal cases before startingLCA: the first option was to select cases based on their coded variables according to PROMIScoding , and the second option was to select those cases who reported at least one symptom inPROMIS questionnaire.2- Calculation : did the investigators included PROMIS GI variables as continuous(quantitative) orcoded variables (1-4) ? Surely the second will limit LCA calculation ability.3- Fitness of model: Table three summarizes options for LCA clustering and shows that 2 classesare more suitable that 3 in initial step ( please consider above-mentioned item 1 about inclusionagain) ; both p value and entropy do not support three clusters.
4- The authors stated : "Taken together, the symptom patterns for the mild and moderate groups
were consistent with IBS mixed or unclassified sub-types following the Rome IV diagnosticcriteria." How did the researches reached to this conclusion ? According to Rome IV criteria IBSis abdominal pain that is related to bowel movement and the questionnaire items in R4Q is mainlybased on this definition.5-Long descriptions about epidemiology of IBS in introduction and discussion are not essential .6- Last paragraph of discussion about role of gut microbiota seems to be unrelated to this study .7- The main LCA is based on GI related variables , as the authors described in parts their draft gut-brain interaction is the major pathophysiology of functional disorders, it may be proposed andsuggested that the psychological factors may be included in LCA modelling
Are the methods appropriate and well described?
If not, please specify what is required in your comments to the authors.
NoDoes 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.
NoAre 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 statisticsQuality of written English
Please indicate the quality of language in the manuscript:
AcceptableDeclaration of competing interests
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