Review for 10.1186/s12876-016-0471-y (2016)

Reviewer ’s report  
 
Title: Discounting the Duration of Bolus Exposure in Impedance Tes ting Underestimates Acid 
Reflux  
 
 
Version: 1 Date: 06 Jan 2016  
 
 
Reviewer: Wai-Kit Lo 
 
 
Reviewer's report:  
 
I appreciate the level of care and attention to which the authors have addressed my comments 
and concerns.  Their revisions have greatly clarified my understanding of the stated findings and 
purpose of their paper.  I  believe that the key concept here is that episode -based interpretation of 
impedance testing parameters, to the exclusion of bolus exposure duration, provides limited 
utility in acid reflux assessment.  This is a reasonable conclusion based on the study re sults, and 
in general, the content is sound.  
 
However, the revisions have also led to the realization that my concerns arise mainly from the 
use of "impedance testing" and "impedance" in the title and throughout the paper.  At our 
institution, bolus durati on is regularly considered in the assessment of reflux diagnosis based on 
impedance testing parameters, perhaps representing some variability in practice from the authors' 
institutions.  Thus, "impedance testing" does not by default discount consideration of the 
duration of bolus exposure.  This is an important and not insignificant point, especially as reflux 
duration is increasingly reported and used in the clinical assessment of reflux and related 
disorders.  Indeed, impedance parameters have been shown to have greater predictive value than 
pH parameters in GERD -related applications specific to pulmonary disease (Gavini, et al. 
Idiopathic pulmonary fibrosis is associated with increased impedance measures of reflux 
compared to non -fibrotic disease among pr e-lung transplant patients. Neurogastroenterol Motil. 
2015; Lo, et al. Pre -lung transplant measures of reflux on impedance are superior to pH testing 
alone in predicting early allograft injury. World J Gastroenterol. 2015), once bolus duration is 
taken int o account.  
 
Therefore, I would advise revising the title to: "Discounting the Duration of Bolus Exposure in 
Impedance Testing may Underestimate Acid Reflux", or some equivalent.  Additionally, I would 
recommend explicitly stating in the abstract and in the  introduction that the routine interpretation 
of impedance parameters may not always account for duration of the reflux episode, which is 
why this study is important.  I appreciate the expanded discussion (page 13, lines 5 -14) which 
helps to emphasize and clarify this point.  The authors may also wish to qualify with any 
subsequent mention of "impedance testing" or "impedance" that the terms as used in the paper 
refer specifically to the interpretation of episodic impedance data, as bolus duration may be 
regularly included in test interpretation at certain institutions and/or for certain clinical situations.  
 
On a separate note, Page 14, line 7: grammar correction, should be "these differences."  
 
Are the methods appropriate and well described?  
If not, please specify what is required in your comments to the authors.  
 
Yes 
 
Does the work include the necessary controls?  
If not, please specify which controls are required in your comments to the authors.  
 
Yes 
 
Are the conclusions drawn adequately supported by the data shown?  
If not, please explain in your comments to the authors.  
 
Yes 
 
Are you able to assess any statistics in the manuscript or would you recommend an  
additional statistical review?  
If an additional statistical review is recommended, please specify what aspects require further  
assessment in your comments to the editors.  
 
I am able to assess the statistics  
 
Quality of written English  
Please indicate the quality of language in the ma nuscript:  
 
Acceptable  
 
Declaration of competing interests  
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