Review for 10.1186/1471-230X-10-37 (2010)

Reviewer's report
Title:Annual pattern of peptic ulcer hospitalizations: a retrospective analysis of
hospital discharge data of the Emilia-Romagna region of Italy.
Version: 2Date:13 December 2009
Reviewer: Reimar W Thomsen
Reviewer's report:
This is an interesting and generally well-written population-based study of the
annual seasonal incidence of hospitalizations with peptic ulcer disease in an
Italian region comprising ~4 million inhabitants. The data material is impressive
and well-suited for conducting a study of this type, and the literature review is
good.
I have the following comments, all for Major Revision:
Title:
1) I suggest to replace ’annual pattern’ with ’seasonal variation’ as this
expression is used throughout the abstract.
2) I suggest to delete the term ’retrospective’. All analyses are by nature made
’retrospectively’, i.e., after data collection. However, the study is based on data
collected prospectively in the hospital databases since 1998. Thus, I consider
this a prospective study, if any.
Abstract:
3) I think the early introduced expression ’admission due to acute PUD’ is a bit
unclear at this point for the reader. Does this mean admission with complicated
PUD, i.e. bleeding or perforation, or does it just mean acute admission with any
form of PUD? Please rephrase.
4) Final outcome ’fatal’ – please state the denominator/follow-up time for this
outcome (unclear from abstract if this e.g. 30-day or in-hospital mortality is
meant).
5) The expression ’PUD hospital admission were lowest in summer (23.2%)’ etc.
is unclear. Please be precise in the abstract: what means ’lowest’, and 23.2% of
what number? (doesn’t fit with the 62% and 61% cited for autumn and spring)?
6) Conclusions: The very last sentence in the conclusions is confusing, as it
suddenly presents additional results on PUD events divided by total admissions.
These results should be moved to the abstract’s results section. Moreover, these
last results (‘main peak in August-September’) are the opposite of the previous
results (‘nadir was consistently in summer (July/August)’). This is confusing for
two reasons:
1) The additional PUD admission / total admission analysis is not prespecified in
the methods, and it should be. One place in the manuscript’s discussion section,
the authors clearly state that they analyzed their data ‘in two ways’: counts per
month, and versus total admissions. I recommend this to be clearly stated
already in the abstract.
2) The additional analysis is called ‘analysis performed on hospital admission
rates’. A better expression would be: ‘analysis of total admission proportions’,
since period prevalence proportions, not rate ratios, are presented. Please see
my later comment on this.
7) Finally, the phrase: ‘summer low which cannot depend from the expected
reduction of admissions in that period’ is a bit cumbersome. I translate this to:
‘summer low that was independent of the observed general reduction in
admissions during summer’. However, in my understanding the PUD summer low
was not independent of the general admission reduction in the summer, since if
PUD summer events were divided by total summer admissions, the proportion
was actually highest during the summer. Please explain/rephrase.
Main text:
Introduction:
8) I miss some sentences about the potential biological mechanisms behind a
seasonal variation of PUD. I feel there is no obvious relationship between the
seasonality of CVD cited at this point, and PUD variation.
9) Table 1 provides a nice overview of previous studies. I suggest citing these
studies’ main results (e.g. the winter peak) in the Introduction section.
10) The authors call the small size of previous studies ‘a major drawback’ –
please explain why this would be major drawback.
Subjects and methods:
11) Data collection: Please explain why repeated admissions in the follow-up
period can’t be excluded more precisely by using additional data (name etc.) than
birth date only.
12) What about PUD admissions of the same person in the years before start of
the follow-up period 1998, how were such admissions handled?
13) The authors state that they included ‘only admissions directly related to
PUD’. In other words, ‘community’acquired PUD’. However, they include both
first and second discharge diagnoses, with the risk of including admissions for
other conditions than PUD. E.g. elderly patients admitted for acute COPD
exacerbation or CVD events, for which an episode of PUD emerged during
hospitalization, thus mimicking the seasonal variation of COPD or CVD. Analyses
should be repeated for PUD as first diagnosis to test any differences in results.
14) Why is sea level vs. hilly level included as a covariate – please explain.
15) Statistical analysis: the authors use ‘rate’ in a wrong way here and
throughout the paper: ‘we assessed hospital admission rates of PUD, i.e., total
number of ulcer cases/month divided by the total number of all hospital
admissions (…)’ This measure is not a rate, but a proportion. More specifically, it
is a period prevalence proportion = the monthly prevalence of PUD admissions
divided by the monthly prevalence of total admissions. Please reword.
Discussion:
16) I don’t understand the sentence in the beginning of the second page of the
Discussion: “Recent epidemiological surveys show the incidence of PU bleeding
has remained stable, being
responsible for about 50% of all cases, followed by oesophagitis and erosive
diseases”. 50% of what kind of cases?
17) Explanation of results: The authors seem to suggest that their finding of a
PUD summer peak when examining PUD/total admissions is biased by fewer
elective admissions in the summer. An alternative explanation might be that other
common diseases, such as CVD, COPD, and community-acquired infections,
have even more marked summer lows than PUD. Please discuss in the
manuscript.
The review of the present literature is very good, and the presented hypotheses
regarding seasonal variation of NSAID / steroid use and alcohol on the
population level are interesting.
Level of interest: An article of importance in its field
Quality of written English: Needs some language corrections before being
published
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