Review for 10.1186/1471-230X-11-145 (2011)

Reviewer's report
Title:Gastric emptying and small intestinal transit time and motility assessed by
a magnet tracking system
Version: 1Date:23 June 2011
Reviewer: Andreas Steingoetter
Reviewer's report:
This is an interesting and well performed study. Unfortunately, the manuscript
has many shortcomings with regard to definition of used terms, completeness,
data presentation and analysis and reference literature.
- Major Compulsory Revisions
The reviewer does not agree with many definitions and nomenclatures regarding
gastrointestinal physiology used in this manuscript. Gastric emptying, gastric
emptying time, motility index, contraction amplitude have been wrongly used in
the manuscript.
This methodology assessed gastric and intestinal transit rather than gastric
emptying. The term gastric emptying should be confined to the emptying of
meals and macronutrients, however in this study no meal was ingested together
with the pill. Furthermore, the authors should also differentiate between solid
emptying (with the solid having a nutrient content), or the emptying of an
indigestible solid (see Discussion). Please use gastric transit time and gastric
transit instead of gastric emptying.
The term motility index is given in the attached tables, however has never been
defined or mentioned in the manuscript text. This term has been defined and
established based on the manometry data (e.g. see Hansen MB Physiol Res
2002) and should not simply be overwritten or newly defined to avoid confusion
and allow for consistent parameter interpretation in future studies. Moreover, this
parameter does not add any additional information to the tables or presented
data. Please omit this term or provide a different term.
Analysis was partly based on the detected contraction amplitude. It is unclear to
the reviewer how this contraction amplitude was derived from the presented data.
How could the amplitude be separated from overlaying breathing movement?
No information on the applied statistical analysis methods is provided.
MRI has been proven to a valid tool for the noninvasive assessment of
gastrointestinal function. Recently, fluorine MRI has been shown to be feasible
for real time tracking of an ingested capsule and the assessment of small
intestinal motility patterns (Hahn T. et al Magn Reson Med. 2011 Mar 4). The
reviewer is highly surprised about no citation or mentioning of this versatile
imaging technique allowing concurrent determination of the underlying
anatomical information in the manuscript.
Magnetic Marker Monitoring has been mentioned in the introduction, however no
reference is provided to the most recent publication by Goodmann K et al. 2010
(Eur J Pharm Biopharm. 2010 Jan;74(1):84-92) showing the potential of this
technique for the assessment intestinal motility. As general request, an update
and optimization of the cited literature is of need.
Most of the presented figures have poor quality (especiall Figure 1 and 3). Figure
3 is not readable.
Figure legend 4B. Regarding the statement “Most distance through the small
intestine is covered during the period just after pyloric passage and during the
period just before ileocecal passage. These two periods, separated by
approximately 90 minutes, likely reflect phase III of the MMC.”
The conclusion of these observations should depend on the ingestion time point
of the used meals, i.e. the study arm. It is unclear if this data is representative for
all study arms, i.e. also for study arm 3, where the meal was ingested directly
after pyloric passage?
The second last paragraph in the Discussion tries to highlight the underlying
inaccuracy of the MTS-1 system. It would be of interest to get a rough idea on
the accuracy of the derived parameters by the MTS-1 system considering the
mentioned inaccuracy.
Please make sure to provide correct figure numbers and figure captions.
- Minor Essential Revisions
I very much appreciate the presentation of individual data in the tables. However,
the authors should think about a more compact representation of the data.
Namely, to skip depend parameters like progression and motility index, therefore
including individual frequency and velocity. Showing the data agreement using
Bland-Altman plots may be useful.
Page 9 please check wording in first paragraph
Please also provide the density of the applied magnetic pill, the PillCam and the
magnet-PillCam
Figure 4 should be changed to a 3D surface plot for better visualization and
understanding.
Could the authors please comment on the use of two different meals for study
arms two and three?
Page 12. The last sentence of paragraph two includes 8 references but adds no
additional information to the first sentence of this paragraph.
- Discretionary Revisions
Was the correction of the respiratory motion always accurate and successful?
The time woindow for StFT was always shifted by 10 samples, i.e. by 1 second
correct?
Level of interest: An article of importance in its field
Quality of written English: Needs some language corrections before being
published
Statistical review: Yes, but I do not feel adequately qualified to assess the
statistics.
Declaration of competing interests:
I assume that I have some non-financial (research based) competing interests in
relation to this paper since I am using a different technique (MRI) for the
assessment small intestinal motility.