Review for 10.1186/1471-230X-10-26 (2010)

Reviewer's report
Title:The effects of thiopurine therapy on health-related quality of life in
Inflammatory Bowel Disease patients
Version: 1Date:6 May 2009
Reviewer: Tomm Bernklev
Reviewer's report:
1) Discretionary Revisions: None
2) Minor essential revisions:
Page 7 – HRQOL assessment
The authors have chosen the 36 question version of the IBDQ by Love et al. as
the disease specific HRQOL questionnaire.
Even though I am aware of that other Spanish groups have used the same
version, I would have preferred the use of the 32 question version of the IBDQ by
Irvine et al.
This version has a more wide-spread use and is today recognized as the
standard disease specific questionnaire within IBD research.
The 36 version has another format, the dimensions are different and comparison
to most of the other literature in the field is complicated.
I would like the Authors to comment upon this.
Page 8-9, Study Design and follow up
The patients who discontinued their treatment due to AE’s or AR’s were followed.
Did you obtain HRQOL for those patients as well? And if you did, how were those
scores treated in the overall analysis? Last value carried forward or other
techniques?
Page 9 – Statistics
You have performed several tests as shown in tables 3-5, did you perform any
tests to correct for multiple comparisons, like Bonferroni or other tests?
If not, please comment.
Further, you claim that MID for SF-36 is 5 points, this is debatable. In
non-selected population based samples, it has been advocated for a 5 point MID
as being of clinical significance, but in intervention studies, most authors stick to
a 10 point MID.
Please comment on this in the Discussion, as the difference between statistical
and clinical difference (MID is one way of expressing this) is of great importance
when HRQOL data are presented.
Page 11 – Basal assessment
The HRQOL determined with the IBDQ showed a significant impairment of all
five dimensions compared to inactive Spanish IBD patients. This significance,
was it statistical or clinical or both? Do you have the actual figures?
Page 12 – Basal assessment
No variable was associated with the basal IBDQ score in UC patients.
Why is it so – would you please elaborate around this. Could it be so simple that
the number of patients is too small – a classical type II error?
Page 12 – six-months assessments
In the text you give figures for the median global IBDQ score, but as far as I can
see, no global score for IBDQ are presented in tables 3-5. How is global score
calculated – is it the total mean score or what?
On the same page regarding the SF-36 dimensional score; again, I would like to
see the effect of gender on the scores.
Page 15 – Discussion
The authors find that the bowel symptom score (IBDQ) was the least impaired,
and that this is in contrast to other papers.
Could this be caused by the differences in the two IBDQ versions, particularly if
you take into consideration that several authors have found a different
dimensional structure for the bowel dimension when they have performed a
factor analysis.
Page 17
There was a trend toward better results in the mental health domains for UC and
in the physical domains for the CD.
This is an uncommon observation and need to be commented upon by the
authors.
Is it just by chance, type II error or what?
Table 3: GH is often considered as an “indicator” on the patients general HRQOL
when using the SF-36. However, the SF-36 GH-dimension from 0-6 months
increased with 5,4 points, which is considered to be relatively small, in contrast to
much greater differences for many of the other dimensions.
The same thing can be observed in table 4 for CD patients.
Would you like to speculate on this?
Table 4: The UC patients have in general lower basal HRQOL scores than the
CD patients. One could therefore speculate that they had a greater potential for
improvement than the CD patients, but this is not the case. The authors think that
one possible explanation is that the UC patients had more severe disease – and I
agree that this would influence the figures.
But one other possibility is that the effect of thiopurine therapy differs between
the two diagnoses.
Please comment.
Figure 1
Instead of the present figure, I would have liked to see a figure with UC, CD and
Spanish GP as separate lines for 0 and 12 months (6 can be omitted).
Major compulsory Revisions
Page 11:
Further, on the same page, several demographic and clinical variables were
tested against the HRQOL scores, but what about gender? It is well known from
the literature that HRQOL scores differ between gender, both in normal
populations and in patient groups.
Did you test for this and what did you find? Or, if you didn’t test for it I would like
a comment from you.
Table 1: Was data on education and co-morbidity obtained? Both are known to
influence HRQOL scores significantly. If not included, please state why.
Table 5.
The HRQOL pattern and scores differs between the two diagnoses. As a
consequence, table 5 is of no interest and should be removed from the paper.
Level of interest: An article of importance in its field
Quality of written English: Acceptable
Statistical review: Yes, but I do not feel adequately qualified to assess the
statistics.
Declaration of competing interests:
'I declare that I have no competing interests'