Reviewer ’s report  
Title: Patterns of m issing data in the use of the Endometriosis Symptom Diary  
 
Version: 1 Date: 27 Jan 2018  
 
Reviewer: Amr Mahran  
 
Reviewer's report:  
This well -written manuscript presents an interesting evaluation of patients' factors associated 
with missing data reporting for En dometriosis Symptom Diary.  
 
Specific comments:  
* Most of the included patients were followed for 12 weeks. Stratifying the patients according 
to the reference periods, in my opinion, might be a source of bias to the results of the study. 
This is because e ach reference period can include patients who just started (more excited to 
report their data) and others who were almost done. Incidence of missing data might increase 
towards the end of each subject's participation in the study.  Instead, I wished the au thors to 
stratify their patient according their participating period in the study for example every two 
weeks (of the 12 weeks) - reporting the data for the 1st two weeks, 2nd two weeks and so 
on…. Here, the number of patients would be almost the same in e ach group and the analyses 
will be more accurate as you control for that.  
 
* For those patients who had their management changed and were followed for another 12 
weeks, is there any change in the incidence of the missing data compared to their first 12 
weeks? 
 
* Regarding the impact of disease severity on the missing data, measuring the means of pain 
scores on the day before and the day after cannot provide an argument. A patient could have a 
low to moderate pain these days and she was able to fill out the diary. However, the same 
patient might have a severer pain on certain day and this prevented her from entering the data.  
 
* Have the authors tested the proportions of missing data in African Americans versus 
Caucasians? Did the authors consider this when comparing between US and Germany?  
 
* P9, L 197 -199 "Subpopulation analysis": What do the denominators (136, 549 and 267) 
represent? They are confusing. The number of participants from US was 133 and from 
Germany was 135 according to table 1.  
 
* There are m ultiple post -hoc analyses for comparing continuous data among multiple groups. 
Please, include the type of post -hoc used and which stats program was used for the study 
analysis.  
 
Are the methods appropriate and well described?  
If not, please specify what is required in your comments to the authors.  
No 
Does the work include the necessary controls?  
If not, please  specify which controls are required in your comments to the authors.  
No 
Are the conclusions drawn adequately supported by the data shown?  
If not, please explain in your comments to the authors.  
No 
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 speci fy what aspects require further 
assessment in your comments to the editors.  
I am able to assess the statistics  
Quality of written Engli sh 
Please indicate the quality of language in the manuscript:  
Acceptable  
Declaration of competing interests  
Please complete a declaration of competing interests, considering the following questions:  
1. Have you in the past five years received reimbursement s, fees, funding, or salary from an  
organisation that may in any way gain or lose financial ly from the publication of this 
manuscript, either now or in the future?  
2. Do you hold any stocks or shares in an organisation t hat may in any way gain or lose 
financially from the publication of this manuscript, either now or in the future?  
3. Do you hold or are you currently applying for any patents  relating to the content of the 
manuscript?  
4. Have you received reimbursements,  fees, funding, or salary from an organization that 
holds or has applied for patents relating to the content of the manuscript?  
5. Do you have any other financial competing interests?  
6. Do you have any non -financial competing interests in relation to this  paper?  
If you can answer no to all of the above, wr ite 'I declare that I have no competing interests' 
below. If your reply is yes to any, please give details below.  
 
I declare that I have no competing interests  
 
I agree to the open peer review policy of the journal. I understand that my name will be included 
on my report to the authors and, if the manuscript is accepted for publication, my named report 
including any attachments I upload will be posted on the website along with the authors' 
responses. I agree for my report to be made available under an Open Acc ess Creative Commons 
CC-BY license ( http://creativecommons.org/licenses/by/4.0/ ). I understand that any comments 
which I do not wish to be included in my named report can be included as confidential comments 
to the editors, which will not be published.  
 
I agree to the open peer review policy of the journal