Review for 10.1186/s12876-023-03037-2 (2023)

Title: Association of serum vitamin D levels on Helicobacter pylori infection: a Retrospective
Study with Real-World Data
Version: 1 Date: 07 Sep 2023
Reviewer's report:
In this study, Liu Dan et al reported the association between H. pylori infection and serum
vitamin D. They found “lower serum vitamin D levels may be associated with an increased
risk of H. pylori infection, and lower serum vitamin D levels are an independent risk factor for
increasing H. pylori infection rates.” I have some questions and comments:
1. Authors used the word “effect” in the topic of study. Because vitamin D is not produced
by stomach, serum vitamin D may influence the immune status of stomach via the vitamin
D receptor (VDR). The condition of H. pylori infection could be influenced by vitamin D
concentration (such as giving potent vitamin D agonist) in cell line or in vivo studies. The current
study does not included VDR data, host immune condition or giving vitamin D agonist test.
Hence, this study could just give “association” information, not “effect”.
2. Authors should give the rational reasons in the introduction to explain why H. pylori infection
associated with serum vitamin D. The section of current introduction is brief but too short. The
initial part (previous studies about vitamin D and H. pylori in the discussion section may be
moved to the introduction section.
3. Table 3 (Univariate analysis of factors influencing H. pylori infection) is more like the
demography table. Table 3 may be changed into table 1 and let readers realize the characteristics
of participants first. But the definition of items in the table3 is not reported, such as “Hygiene
of dining place, n (good/poor)”, “Main source of drinking water, n (clean/probably polluted)”
and “Drinking untreated water, n (yes/no)”. Authors may explain the condition of good hygiene
of dining place, polluted water, untreated water…
4. Could authors give the information of H. pylori infection prevalence in the study areas?
According to table 3, among the people with mean age 47-48 y/o, the H. pylori infection rate is
61.80% (415/415+257). Is the H. pylori infection rate higher than the local infection rate?
5. In this study, the cut point of vitamin D deficiency is < 20 ng/ml (dichotomy). Could authors
give the reference of using 20 ng/ml as cut point ? Is there any data from Chinese people? How
about using the three or four quarter of serum vitamin D value to see the association of H. pylori
infection?
6. In exclusion criteria, people with previous history of H. pylori infection were excluded. Most
people, who had a history of H. pylori infection but didn’t receive H. pylori eradication therapy,
would keep the infected status. When they receive C13 urea breath test (UBT), the result of UBT
may be positive. Hence, they may be not excluded. Hence, “a history of H. pylori infection” as
exclusion criteria may be corrected as “ a history of H. pylori eradication therapy”.
7. Minor correction:
Helicobacter pylori is abbreviated as “H. pylori” or “Hp” in the text. Suggest unified as “ H.
pylori”. By the way, the word should be italic.
Give a study flow chart (diagram) to show how the participants enrolled in this study.