Review for 10.1186/s12876-024-03353-1 (2024)

Title: Association between serum vitamin D status and severity of liver cirrhosis: Implications
for therapeutic targeting in Nigerian patients
Version: 2 Date: 28 Jun 2024
Reviewer's report:
The idea of a study of the correlation between the serum vitamin D levels and the severity of
liver cirrhosis in a sunny country as Nigeria is interesting. The cross sectional study is the right
study to evaluate the mentioned association. Even though the presence of a comparison group
of healthy patients wasn’t strictly necessary it has been included. Nevertheless, I have some
major concerns regarding this paper. Since the purpose of the study is to evaluate the relationship
between serum vitamin D and the degree of cirrhosis based on CPS and MELD, as declared
in the “materials and methods” section, some conclusions are not consistent with the chosen
type of study. As you correctly declare in the paragraph of the limitations of the study, with
a cross sectional study it’s only possible to show associations between the considered groups
(different degrees of liver cirrhosis) and the variable chosen (vitamin D levels); for instance
the last sentence in pag. 14 (the high burden of advanced liver cirrhosis among individuals
with vitamin D deficiency or insufficiency, may suggest the need for targeted interventions
to improve vitamin D status and potentially mitigate disease progression), is not supported by
the data showed. To support the sentence above a group of patients with vitamin D deficiency
has to be evaluated, not the group of patients with liver cirrhosis with vitamin D deficiency.
Furthermore, in the following sentence at the beginning of pag. 15 (the significant strong
negative correlations between serum vitamin D level and liver cirrhosis severity in this study
indicates that higher levels are associated with less severe cirrhosis suggesting a potential role
of vitamin D in modulating disease progression) cannot be deduced form de conducted cross
sectional study. With a cross sectional study the only conclusion can be, in this case, the measure
of the prevalence of the vitamin D value in the studied groups. For the same reason the following
sentence, in the same paragraph (Its observed association with liver cirrhosis suggests that
optimizing vitamin D status may have therapeutic implications in managing this condition) it’s
not a conclusion consistent with a cross sectional study. Again in the conclusion section is
mentioned a potential therapeutic role of the vitamin D, and even in this section this sentence
is not consistent with the conducted study. For these reasons even the title of the manuscript
stresses too much the focus of the study on the implications as therapeutic target, instead of
the prevalence and possibly the prognostic value of the values of serum vitamin D. Again, in
section “discussion”, 1st paragraph, In this study, significant alcohol consumption and history
of hepatitis B viral infection […] increases the tendency to develop liver cirrhosis: even if it is
probabily true, since the study is a cross sectional study it’s not possible to draw this conclusion
from the data you show. You can better say that in the cirrhosis group you observed more patients
with alcohol consuption and history of hepatitis B viral infection rather than in the comparison
group.
However, all these major suggestion I made, are already mentioned in the manuscript in the
first paragraph of pag. 16. The focus of the discussion and conclusion should be focused on the
prevalence and the potential prognostic role rather than a possible therapeutic target.
In conclusion, the major suggestion is to draw conclusion that are consistent with a cross
sectional study, like prevalence and mesure of association.
Furthermore I have some minor suggestions:
- In the section “material and methods” the inclusion criteria for the comparison group has to be
declared. In pag. 6, 3rd paragraph what does apparently healthy means? In table 1 is reported
that some of them have diabetes and hypertension, maybe you just mean that they don’t have
any liver disease.
- Section “material and methods”,3rd paragraph: since it’s a cross sectional study, I wouldn’t
say the study cohort, it’s maybe better say it differently (eg study group).
- Pag 15, first paragraph: these factors may include dietary habits, cultural practices, and dark
skin colour, all of which can affect vitamin D absorption, conversion, and utilization. The cause
of the deficiency of vitamin D is maybe even the liver disease, so the liver disease can be the
cause, not the consequence, and here it should be mentioned.