Review for 10.1186/1471-230X-12-55 (2012)

Reviewer's report
Title:Risk of inflammatory bowel disease following a diagnosis of irritable bowel
syndrome
Version: 1Date:24 October 2011
Reviewer: Jason Hou
Reviewer's report:
The authors present an interesting manuscript on the association of diagnosis
and IBS and the subsequent diagnosis of IBD among active duty military
personnel using a retrospective cohort study. The authors observed a 15 fold
increased incidence of IBD among subjects with a diagnosis of IBS compared to
non-IBS controls. The authors conclude the data suggest a common or causal
pathway for IBS and IBD.
Major Compulsory Revisions
- The authors should describe how was “new-onset” IBS defined. Was it by date
of first diagnosis code for IBS? This may not account for patients with
pre-existing diagnosis of IBS, and time from IBS to IBD diagnosis may not reflect
the accurate diagnosis time.
- The authors should not use the term “negative colonoscopy” as the results of
endoscopy were not specifically reviewed or analyzed. In an attempt to identify
endoscopy negative IBS, The authors attempted to make a differentiation of
“well-defined IBS” by adding endoscopic criteria of sigmoidoscopy and
colonoscopy within 12 months of IBS encounter and followed by another IBS
encounter within 12 months of endoscopy. However, they only excluded subjects
with IBD diagnosis within 1 yr of IBS index, which suggests that a patient with an
endoscopy within 12 months, and a subsequent encounter with an IBD code
could be included as a “well-defined IBS” if they had another code for IBS. The
authors state that 30% of IBD subjects had continued coding for IBD. This may in
part explain the higher incidence of IBD among the “well-defined IBS” cohort
when compared to the IBS cohort overall. The authors do recognize in their
discussion that IBS patients with more significant symptoms may be more prone
to under colonoscopy and results in selection bias.
- The authors should specify if subjects in the study have access to outside
medical resources or if they are limited to DOD medical care while on active duty.
Medical care and diagnoses prior to Department of Defense medical data were
not included. Patients with a diagnosis of IBS prior to active military duty may
have had endoscopic evaluation which would not be accounted for. Likewise, the
patients may have had a diagnosis of IBD prior to active duty, but have been
misclassified as IBS. The authors do acknowledge the limitations of ICD-9
coding. Have ICD-9 codes for IBS or IBD in the DOD database been previously
validated?
Minor Essential Revisions
- Specify how sigmoidoscopy/colonoscopy was determined- I presume by CPT
- How were patients classified who had diagnosis codes for both UC and CD?
Discretionary Revisions
- The authors conclude that IGE is associated with an increased risk of
development of IBD in the IBS cohort. However IGE encounters without
pathologic/microscopic confirmation may reflect a patient with ongoing GI
symptoms with established history of IBS/IBD. In addition, pts with IBS may be
more likely to seek medical attention for diarrhea/GI complaints and be tested
more frequently with stool tests compared non-IBS controls.
- The authors should discuss that although the relative risk was elevated, the
absolute risk of IBD was low (~1% of IBS cohort) and may still be explained by
limitations of ICD-9 accuracy of either IBS or IBD. The alternative conclusion that
a subset of IBD patients are misclassified or misdiagnosed as IBS due to overlap
of GI complaints remains.
Minor issues not for publication
- Spell out abbreviation “MTF” Methods 2nd paragraph
- Insert publication in introduction, 2nd paragraph, 2nd sentence.
- Use consistent formatting for reference notation in Discussion, paragraph 6.
- Change “an” to “a” prior to FGD in Discussion, paragraph 7
Level of interest: An article whose findings are important to those with closely
related research interests
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