Review for 10.1186/s12876-020-01504-8 (2020)

Reviewer’s report
Title: 
Hepatitis C virus infection and its associated factors among prisoners in a
Nigerian prison 1Ifeyinwa M. Okafor *, Solomon O. Ugwu and 1, U. Henshaw
U. Okoroiwu
Version: 
1 
Date: 
21 Sep 2020
Reviewer's report:
The authors of the manuscript "Hepatitis C virus infection and its associated
factors among prisoners in a Nigerian prison" have studied the prevalence of
HCV infection among jail inmates and its contributing factors. I have the
following comments:
1) The basis for the age categorization in the fashion that has been done is not
clear
2) How do the authors explain the finding of age not being associated with HCV
prevalence in the study cohort?
3) Did the authors try to analyse the presence of multiple risk factors (lets say
>3/4 risk factors) as a predictor of seropositivity, rather a mere chi-squared test
for the overall effect (table 6)?
4) HCV is a chronic infection, with the initial infective period often going
unnoticed. How sure are the authors that the inmates were infected during the
period of incarceration and was not positive prior to that? And, if that is the case,
then trying to correlate high risk behaviour inside the jail and seropositivity
would be conjectural. 
5) How do the authors explain the absence of any significant association between
the risk factors and seropositivity on LR? This could be possibly explained by
the fact that a substantial sub-cohort might be seropositive before being
incarcerated.
6) On one hand the authors state that "prevalence of HCV in this study is higher
than previous study in another prison in Nassarawa State, ... This difference may
be attributed to injection drug use practice (19%) in our studied population…"
While on the other, they mention that "This is further corroborated by low
population of injection drug uses observed in this study." 
The two statements
sound contradictory. 
7) The conclusion of the study, although correct in a general sense, but is not
derivative from the study results.
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Is the study design appropriate to answer the research question (including the use
of appropriate controls), and are the conclusions supported by the evidence
presented?
Yes
Are the methods sufficiently described to allow the study to be repeated?
Yes
Is the use of statistics and treatment of uncertainties appropriate?
No
Is the presentation of the work clear?
No
Are the images in this manuscript (including electrophoretic gels and blots) free
from apparent manipulation?
Yes