Review for 10.1186/1471-230X-11-94 (2011)

Reviewer's report
Title:Psychopathological features of irritable bowel syndrome patients with and
without functional dyspepsia: a cross sectional study
Version: 1Date:30 June 2010
Reviewer: Michael Crowell
Reviewer's report:
The paper addresses an important area that may have implications for the
management of these patients. The background, problem, and conceptual
framework are reasonably articulated. The background and references appear
appropriate and the literature well integrated. The study methods were generally
adequate, but some aspects of the study need further clarification. Overall the
statistical procedures used were adequate for the experimental design, but
several questions were identified that related to the choices for specific analyses
and their interpretation:
Major Compulsory Revisions:
1. The primary limitations of the study are the small sample size, and the large
number of exploratory analyses in different subgroupings. Due to the small
sample sizes, special care should be taken in interpreting the lack of significant
findings between the subgroup analyses, especially between the PDS and EPS.
Another major concern is the repeated analysis of the FD data as a combined
group and then separately as PDS and EPS. These limitations may limit the
generalizability and reproducibility of the findings in the clinical setting. Due to the
very small sample size for this subgroup comparison, the conclusion that there
was “…no significant difference between IBS patients with PDS and IBS patients
with EPS…” is not warranted by the data presented in this study.
2. Please explain why the raw scores were used rather than normalized
T-scores? The T-scores would allow for better interpretation compared to normal
values.
3. Medians should be reported with their associated interquartile ranges in the
Results section of the paper or a table to allow the reader to evaluate the
variability within the groups.
4. Was the distribution of scale scores evaluated for normality? If so, how? Is this
why a non-parametric statistic used for the comparison of SCL-90 scales? If
T-scores were used the distribution would be approximately normal and allow the
use of parametric tests.
5. The P-value for the comparison of the SCL-90 subscales should be adjusted
for multiple comparisons or it should be stated that these adjustments were not
made and why in the Statistical analysis section.
6. How was the sample size chosen for the study? The number of combined
IBS+FD patients seems quite small for the statistical analyses, but adequate.
More concerning is the very small sample size used for the FD subgroup
comparisons. The sample size is much too small conclude that a negative
statistical finding infers that there is no differences between subgroups. The lack
of significant findings may be solely due to lack of statistical power to identify
differences (Type II error). The discussion and conclusion should clearly state
this fact and not over state that there were no differences between subgroups.
7. Discussion, 2nd paragraph. In the sentence “The present study shows a high
frequency of overlap between IBS and FD, equal to 31.7%, with no significant
difference between PDS and EPS, supporting previous findings.” it is not clear
what is meant by “with no significant difference between PDS and EPS,
supporting previous findings”. Please clarify.
8. Discussion. Limitations should be discussed more fully.
9. Figure 1. Please double check the significance for the Phobic Anxiety subscale
as the differences seem extremely small?
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'