Review for 10.1186/1471-230X-12-79 (2012)

Reviewer's report
Title:13-Year Mortality Trends among Hospitalized Patients with Inflammatory
Bowel Disease
Version: 1Date:31 January 2012
Reviewer: Ashwin N Ananthakrishnan
Reviewer's report:
Sewell and Yee use the National Hospital Discharge Survey, a national
hospitalization database to examine the trend in in-hospital mortality in IBD
patients over a 13 year period between 1994 and 2006. They demonstrate a
reduction in odds of in-hospital death for UC over this time period with no
temporal changes in Crohn’s disease deaths.
While their work is interesting, I have a several concerns about their methods.
These stem from incomplete adjustment for risk factors for in-hospital mortality
and lack of information on cause of death or reason for hospitalization, thus
limiting interpretable actionable information that is available from this manuscript.
However, I believe that it may be possible to address these concerns even within
the limitations of the NHDS as such information is usually contained within these
administrative databases.
Major Compulsory Revisions
1. One major limitation is the lack of information on co-morbidity. Even in
administrative databases like the NHDS, it may be possible to use modifications
of the Charlson index or Elixhauser index, both of which are available for use
with such databases, to estimate co-morbidity burden. While the authors discuss
the correlation between age and co-morbidity, such a relationship is not fully
co-linear and in many analyses, both turn out to have independent effects on
predicting mortality.
2. A second significant limitation of the study is the lack of information provided
on the reason for hospitalization or diagnoses associated with the hospitalization.
As stated by the authors in their manuscript, mortality due to IBD is extremely
uncommon, particularly in comparison with other causes of death in patients with
IBD. Without information on other potential reasons for the hospitalization (some
of this can be ascertained even from administrative databases like the NHDS), it
is impossible to interpret their findings of decreased mortality. Is this due to
improvement in IBD care (as they suggest in several places in their manuscript)
or improvement in cardiovascular care (if most deaths are due to cardiovascular
disease) or due to changes in the management of serious infections or temporal
improvement post-operative management? Thus, it is apparent that the crude
mortality trends could be influenced by any number of potentially important
variables, limiting the value of overall mortality trends alone.
3. Were patients with any diagnosis of IBD included or was the analysis restricted
to those with a primary diagnosis alone? It would be interesting to see the trends
presented separately for primary IBD diagnosis vs. secondary IBD diagnosis.
Minor Essential Revisions
4. The opening paragraph of the background focuses on biologic therapies.
However, medication information is not available in NHDS, and as such,
discussion about the impact of medical therapies remains speculative and should
be avoided if possible given the limitations of the database.
Level of interest: An article of limited interest
Quality of written English: Acceptable
Statistical review: Yes, and I have assessed the statistics in my report.
Declaration of competing interests:
I declare that I have no competing interests