Review for 10.1186/1471-230X-14-182 (2014)

Reviewer's report
Title:The severity of irritable bowel syndrome or the presence of fibromyalgia
influencing the perception of visceral and somatic stimuli
Version:1Date:27 April 2014
Reviewer: Daniel Keszthelyi
Reviewer's report:
The article by Tremolaterra et al. investigates the effect of co-morbid fibromyalgia
on somatic and visceral perception in IBS patients. This topic is of relevance for
increasing the understanding of nociceptive processes in chronic pain conditions,
which is needed for optimization of treatment regimes in this patient group, in
particular IBS. The reader is left, however, without a clear explanation for the two
most salient findings from this study (see below).
- Major Compulsory Revisions
1. Patients with severe IBS and comorbid FMS appear to have visceral
hypersensitivity to a lesser degree than patients with severe IBS but without
FMS. This appears to be the most important finding from this study. However,
this finding is not explained sufficiently in the discussion. The authors mention
that more severe diseased condition leads to central disinhibition resulting in
higher perception levels. Although I agree with this statement, this does not
explain why severe IBS patients with FMS have lower perception levels than
severe IBS patients without FMS. An explanation for this phenomenon could be
the involvement of alternative descending pain-modulatory pathways, which are
activated through painful somatic stimuli (due to FMS) and hence attenuate
incoming visceral nociceptive information. Conversely, this mechanism can work
vice versa for attenuating somatic perception. It would therefore be interesting to
know what the severity of the FMS was in the IBS patients who had this
condition.
Another possibility is viscera-somatic conversion on spinal level (see also
Wilder-Smith Gut 2011 for an extensive review), which can also explain the
observed phenomena.
2. Patients with comorbid FMS have significantly higher somatic perception
scores than patients without FMS, regardless of the severity of IBS. To me it
seems that this finding does not support that IBS patients have altered somatic
perception, unless they also have FMS, as without comorbid FMS, these patients
had somatic pain scores below 2.
On the other hand, it may very well be the case that these ‘pure’ IBS patients
have somatic hypoalgesia, as shown by others previously, but this aspect cannot
be assessed on the basis of these study results due to the fact that there were no
healthy volunteers included.
Conversely, the inclusion of a patient group with FMS only (so no comorbid IBS)
would be able to further clarify the issue.
The study in its current form does not allow to draw conclusions with regards to
nature of changes in somatic perception in IBS patients.
- Minor Essential Revisions
1. The authors mention that rectal hypersensitivity correlates with symptom
severity, referring to Posserud et al. I would also mention this correlation is weak.
Furthermore, it would be interesting to look at the data in a different way, namely
by splitting up the IBS group by terms of rectal hypersensitivity and
normosensitivity, instead of symptom severity. I believe that this would more
closely reflect the relationship with somatic perception.
2. How was the severity of IBS defined? Which cut-offs were used?
3. Please include a power calculation in the manuscript.
4. Introduction: The authors state that IBS patients commonly have visceral
hypersensitivity. I would correct this to 35-60% as stated later in the discussion
section.
5. Is sodium diocthylsulfosuccinate or sorbitol known to influence rectal function?
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