Review for 10.1186/1471-230X-13-104 (2013)

Reviewer's report
Title:Prevalence and risk factors of Helicobacter pylori infection in Korea;
Nationwide multicenter study over 13 years
Version: 1Date:10 March 2013
Reviewer: Leonardo Henry H Eusebi
Reviewer's report:
I read the study by Kim and co-workers with interest.
This is a multi-centre nationalwide study reporting the seroprevalece of H.pylori
infection in several areas of South Korea in 2011, also reporting factors
associated with seropositivity.
Major findings are that the seroprevalence of H.pylori infection has progressively
reduced since 1998 and 2005, and that among several know factor associated
with seropositivity such as male gender, economic status and education level,
also high cholesterol levels was highlighted as an associated factor.
The study has a similar design as 2 previous Korean nationalwide surveys
conducted to investigate the seroprevalence of infection in 1998 and 2005. This
has allowed also to compare the results of the actual study with the 2 previous
ones.
However, several important topics need to be clarified:
Major Compulsory Revisions
1. It is stated in the “comparison of trends of seroprevalence” section that the
trends were compared using the published data of 1998 and 2005. Thus, it
should be cleared how the authors manage to divide the study population in to 8
birth cohort intervals with relative seroprevalence values for 1998, 2005 and
2011 when such values are not reported in the studies of 1998 and 2005.
2. In table 3 reporting the risk factors, the total number of included subjects is
10796. However, the total of subjects divided by household income is 9449, by
education is 10188, by BMI 10657, etc. The authors should explain howcome
there is lacking data about patients when considering each risk factor. Patients
with incomplete data should be excluded for the analysis.
3. The decrease of prevalence divided by age (intervals of 10 years), as shown in
figure 2C, was statistically significant from 1998 to 2005 (and thus also between
1998 and 2011), but was not significant between 2005 and 2011. This important
result should be stressed in the discussion, since although there is a reduction in
the last 6 years, this is not statistically significant.
4. According to figure 2A there is a statistically significant reduction only between
data from 1998 and 2011. It is not clear whether there is also a statistically
significant reduction between 2005 and 2011. This point should be clarified.
5. The English spelling and grammar should be reviewed by a native
English-speaker.
Minor Essential Revisions
6. As reported in the methods section, patients underwent only questionnaire
testing and seroprevalence of infection. However during the study the authors
report also blood test values (Cholesterol, glucose, triglyceride) and
anthropometric values (weight, BMI). These evaluations (physical examination,
blood testing, etc.) should be mentioned in the methods section.
7. Was the questionnaire used the same as for the previous studies?
8. In the “Analysis of cohort effects” section the Authors state that “the data from
1998 was considered to be those in 1999 because the successive
cross-sectional data should span with same interval”. Doesn’t reducing the time
interval from 7 to 6 years modify the statistical validity and result? The Authors
should comment such statisitcal adjustment.
9. Figure 3 line H has a wrong symbol.
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Not suitable for publication unless extensively edited
Statistical review: No, the manuscript does not need to be seen by a
statistician.
Declaration of competing interests:
I declare that I have no competing interests