Review for 10.1186/s12876-019-0984-2 (2019)

Reviewer ’s report  
 
Title:  The association of liver function and quality of life of patients with liver cancer  
 
Version: 1 Date: 30 Jan 2019 
 
Reviewer:  Research  Square  
 
Reviewer’s report:  
 
"STATISTICAL REVIEWER ASSESSMENT:  
 
Is the study design appropriate for the research question (considering whether the analyzed 
population accurately reflects the design and whether you see any problems with 
control/comparison groups, e.g., likely confounders)?  
 
No - there are minor issues  
 
 
Are methodologies adequate and well implemented (considering whether assumptions are 
addressed and whether analyses are robust)?  
 
No - there are major issues  
 
 
Are the analyses adequately communicated (considering whether reporting details are adequate 
and wh ether figures and tables are well labeled and described)?  
 
No - there are minor issues  
 
 
Does the interpretation accurately reflect the analyses without overstatement (considering 
whether limitations/bias are acknowledged and whether accurate descriptors, e. g., 'significant', 
are used?  
 
Yes - interpretation accurately reflects analyses, limitations/bias are acknowledged, accurate 
descriptors are used  
 
 
Could an appropriately REVISED version of this work represent a statistically sound 
contribution?  
 
Probably - with minor revisions  
 
 
STATISTICAL REVIEWER COMMENTS:  
The authors have collected quality of life (QoL), demographic, clinical and laboratory data to 
examine the relationships between these variables. This is a straightforward design that should 
allow the s tudy objective to be addressed.  
 
A large number of correlation coefficients are conducted along with regression analyses. In 
general, these statistics are appropriate, although the authors need to address some of the 
assumptions and decisions they make (as  noted below). Also, it is possible for the authors to 
conduct biserial correlations rather than univariate logistic regressions, but one is not more 
correct than the other, so it is a matter of personal preference.  
 
 
REQUESTED REVISIONS:  
 
It would be usefu l to know if all of the data was collected for the same time period. In particular, 
it could be the case that the laboratory data represents results of samples that were taken some 
time before quality of life data was collected, so they might not represent  patient data at the same 
points in time.  
 
In the statistical analysis section the authors state that QoL variables that had p values less than 
0.0001 in univariate logistic regressions were included in multivariate logistic regression. Yet, no 
justificati on is provided for choosing variables based on this p value. Choosing variables based 
on a p value alone is generally a poor idea, especially when many statistical tests are being 
conducted, as there is the potential to inflate the Type I error rate. There fore, selecting variables 
based on a justified effect size would be more appropriate.  
 
The authors indicate that they transformed liver function variables to meet the assumption of 
normality but for which test? It seems that these transformed variables wer e used in Spearman's 
rho and logistic regression tests, so why did the authors assume that normality was 
required?Also, if transformations were deemed appropriate for liver function variables, why 
were they not also conducted for the QoL variables?  
 
Correl ation values greater than an absolute value of 0.3 were determined to be clinically 
important. This decision requires further justification, especially as it affects the interpretation of 
findings.  
 
There is no need to report statistics (such as correlation coefficients and p values) to 4 decimal 
places - 2 decimal places is sufficient and you should not go beyond 3 decimal places.  
 
The results of the correlation analyses are presented in detail in th e text. This is unnecessary as 
the information is also presented in tables. Rather, a concise summary could be presented in the 
text." 
 
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 comm ents 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 manuscript:  
 
Needs some language corrections before being published  
 
Declaration of competing interests  
Please complete a declaration of competing interests, consideri ng the following questions:  
 
1. Have you in the past five years received reimbursements, fees, funding, or salary from an 
organisation that may in any way gain or lose financially from the publication of this 
manuscript, either now or in the future?  
 
2. Do you hold any stocks or shares in an organisation that 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 -financi al competing interests in relation to this paper?  
 
If you can answer no to all of the above, write 'I declare that I have no competing interests' 
below. If your reply is yes to any, please give details below.  
 
This reviewer  has been recruited by a partner organization, Research Square. Reviewers with 
declared or apparent competing interests are not utilized for these reviews. This reviewer has 
agreed to publication of their comments online under a Creative Commons Attributio n License 
attributed to Research Square and was paid a small honorarium for completing the review within 
a specified timeframe. Honoraria for reviews such as this are paid regardless of the reviewer 
recommendation.  
 
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 websi te along with the authors' 
responses. I agree for my report to be made available under an Open Access 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