Review for 10.1186/s12876-020-01485-8 (2020)

Reviewer’s report
Title: 
Changes in hepatic fibrosis and vitamin D levels after viral hepatitis C
eradication using direct-acting antiviral therapy
Version: 
1 
Date: 
19 May 2020
Reviewer's report:
Sriphoosanaphan et al. showed that improvement of hepatic fibrosis after viral
hepatitis C eradication using DAA.
Although the result seemed reasonable, there are several issues to be solved.
I think the following points will further improve the quality of your paper.
1. It is already known that DAA therapy improves liver fibrosis (fibrosis
biomarkers, LSM), so the conclusion of this paper is lacking in impact.
Furthermore, it is said that the decrease in LSM after hepatitis treatment does not
purely reflect liver fibrosis.
2. The title gives the impression that vitamin D has also improved, but the results
are different and confusing to the reader.
3. Abstract Background; "VD deficiency progresses liver fibrosis." Is this true?
Surely, Ref. 4 said vitamin D receptor knock out mice develop liver fibrosis. But
I don't think this is synonymous with vitamin D deficiency. 
4. Line 68; "direct antivirals" makes sense, but "direct-acting antivirals" is better
along with the abstract.
5. Statistical analysis; Nonparametric tests may not be suitable for clinical data.
Because it is often not a normal distribution.
6. Discussion; The points to be discussed are off. Readers want to find out why
vitamin D doesn't get better when liver function improves.
7. Table1 Treatment regimen; What is SOD? There are two abbreviations for
ledipasvir (LED, LDV).
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.
Unable to assess
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 recommend additional statistical review
Quality of written English
Please indicate the quality of language in the manuscript:
Not suitable for publication unless extensively edited
Declaration of competing interests
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