Review for 10.1186/1471-230X-12-39 (2012)

Reviewer's report
Title:Postoperative Complications Following Colectomy for Ulcerative Colitis: A
Validation Study
Version: 1Date:22 August 2011
Reviewer: Ashwin N Ananthakrishnan
Reviewer's report:
There has been growing interest in the use of administrative database in IBD
research. However, because of the de-identified nature of several of the
databases used, there have been limited validation studies. In this manuscript,
Ma and colleagues examine validity of codes of UC in administrative databases
with specific focus on identification of colectomy, nature of colectomy (emergent
vs. elective), pre-operative comorbidities (using the Charlson and Elixhauser
indices) and post-operative complications. They then compare the predictive
value of variables identified using administrative data to those identified through
chart review.
The manuscript is well written and the methods explained in great details. The
scope of the manuscript is fairly extensive with attempts made by the authors to
simultaneously validate the study population, predictors, and various primary
(colectomy) and secondary (post-op complications) outcomes.
I do not have any major concerns about the manuscript and find it to be useful to
researchers in IBD, particularly those using administrative database. I appreciate
the authors not restricting their validation study to just defining UC, but extending
it to examine accuracy of comorbidities, complications and outcomes.
One concern with validation studies using specific population-based databases is
portability to other electronic health record systems but the authors address
some of this in their discussion.
Discretionary Revisions:
1. Because of the fairly extensive scope of the manuscript, a more orderly and
systematic presentation of results may be easier for the reader to follow. For
example, in their results section – the authors start by discussing risk factors for
post-operative complications from administrative vs. chart review data, but in my
opinion, this become relevant only after they have commented on the validity of
administrative codes for UC, for the comorbidities, and outcomes. Thus, the
orders of some of the results subsection may be restructured to represent a more
systematic approach.
2. They examine Charlson comorbidities as a dichotomous variable (0, >1). How
does the administrative data perform when these co-morbidities are divided into
a greater number of strata (for example, 0,1,2,>3 comorbidities) as used by
several authors?
3. In their ascertainment of the accuracy of codes for colectomy, were there any
colectomies for dysplasia or cancer? Where such patients and procedures
included in the UC flare cohort (even though their procedure was not for a
disease flare)?
4. How were patients with a history of UC, now with an ileostomy or ileal pouch
post-colectomy handled? Were they treated as a ‘false positive’ or a ‘true
positive’?
5. I appreciate the authors’ careful attempt to validate the post-op complications
grouped by various systems. Did they perform any validity studies for specific
post-operative complications? Some post-op complications may be of greater
interest than others including wound infections, pneumonia, cardiac events or
ileus.
6. I’m curious about the low specificity for the post-operative complication codes,
particularly since these are typically distinct from the co-morbidity codes that may
mimic post-operative events. What were some of the false positive post-operative
complication codes?
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Acceptable
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