Review for 10.1186/s12876-021-01782-w (2021)

Reviewer’s report
Title: 
Prevalence of and risk factors for Metabolic associated fatty liver disease
in an urban population in China: a cross-sectional comparative study
Version: 
0 
Date: 
28 Feb 2021
Reviewer's report:
This is a cross-sectional study in evaluating the prevalence of metabolic
associated fatty liver disease in China in a health examination population. The
population size was large, but whether it can represent the population of China
wasn't evident. Many wrong grammar or words use were frequently noted in
abstract and article. The English grammar and words use may be further edited
by native-English advisors. Some results are duplicated mentioned in table and
the result text, and again in discussion. In discussion, some cited literature were
based on NAFLD, not MAFLD which may need further correction and
condensed. 
Major issues: 
1. This study is a hospital based study rather than a territory-cohort study, or a
country-wide random sampling study. How this population represented the
population of China? In a previous study, the prevalence of MAFLD in China
had been reported.(Su Lin et al. Liver Int . 2020 Sep;40(9):2082-2089.) What's
new finding in this study compared with previous China studies?
2. What is the proportion of patients of different age in this study? Is it the same
with the age distribution in China?
2. Evaluation of hepatic steatosis is the key component in diagnosis of MAFLD,
please make detailed and clear definition about it. Is elastography used, or sono-
guided liver histology evaluation? or other blood biomarkers/scores used? If only
by sonography, may the prevalence of MAFLD underestimated in this study?
3.Is there any difference between patients different subgroups of MAFLD
patients, overweight or obesity, normal/lean weight and Type 2 DM?
4. About the measurement of blood pressure, did patients with hypertension
allowed to receive medication at the exam date, if not, how long were they asked
to stop the medication. If not stopped, how much patients had taking HTN
specific medication already? Similar condition and question on patients taking
DM, hyperlipidemia medication treatment. If not stopped, what is the size of
population, since this may influence the value of blood pressure and lab data in
this study. 
5. Since viral hepatitis is an important issue in Asia, how many patients have
coexisting HBV and HCV disease.
6. How many patients having MAFLD related cirrhosis? The drop of prevalence
in patients older than 55 years old may be due to MAFLD related cirrhosis
causing disappearance of metabolic disorders parameters. 
7. How many patients found with liver steatosis by ultrasound not fulfilling the
criteria of MAFLD in this study? If only <1% of patients didn't fulfill the
criteria, may ultrasound only be used for the diagnostic criteria of MAFLD? If
much patients didn't fulfill the criteria, what is their cause of liver steatosis? Did
they differ from those with MAFLD related liver steatosis?
8. Since the authors found may risk factors of MAFLD, will there be a set of
parameters score that had highest prediction ability of MAFLD in China? 
Minor issues:
1. Did the participants sign informed consent?
2. May male and female have different normal range of Liver function tests?
3. Did the staff doing ultrasound blind to the laboratory data or history of the
patient?
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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?
No
Are the methods sufficiently described to allow the study to be repeated?
Yes
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Yes
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No
Are the images in this manuscript (including electrophoretic gels and blots) free
from apparent manipulation?
Yes