PONE-D-20-31835

Seroprevalence and risk factors for hepatitis B and hepatitis C in the general population of Kazakhstan

PLOS ONE

Dear Dr. Issanov,

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Reviewers' comments:

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Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: No

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Reviewer #1: No

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Reviewer #1: Yes

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5. Review Comments to the Author

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Reviewer #1: Overall this is an interesting paper that describes an important disease globally and in Kazakhstan. The paper estimated hepatitis B and hepatitis C for a representative sample of the Kazakhstan population for three large oblasts (provinces). The goal was to relate seroprevalence estimates to several demographic or sociological factors. While important work, there are several major methodological issues that need to be addressed before consideration for publication.

ABSTRACT: there are abbreviations for the viruses used in the abstract that need to be spelled out like the authors did in the first paragraph of the introduction.

INTRODUCTION: I'm concerned about calling this a national study when only three oblasts were used to represent a landscape as largest as Kazakhstan. Having been there and worked there for several years, I appreciate that these three areas represent a large proportion of the population. However, I do not think the authors have done enough to describe the distribution of people or describe the proportion of people outside of these three areas and how they may or may not differ from those inside of the study area. I'm not sure it is fair to call this national as designed or at least described.

METHODS: there are several issues that must be addressed prior to consideration for publication.

First, as a serological surveillance study I would expect to read a much more clear methodology of how samples were collected, processed, and the serological tests performed. Overall, the methods section lacks appropriate citations and detailed enough methodology to repeat this work. Without expanding on both citations in detail this work should not be considered reproducible.

In the discussion of the data variables for this study, the authors provide very little information on how urban and rural were defined. These terms are specifically defined in a variety of studies using different cutoffs for population density. Likewise, across these three regions of Kazakhstan, there is a growing periurban environment where rural migrants are moving closer to the city and the city suburbs are expanding into the rural area. This study at a minimum needs to define urban and rural.

The larger issue with this study is the use of backward stepwise variable selection for the regression modeling. It has been well known for many years now that stepwise selection techniques are losing favor and there is a large body of statistical literature describing why. It has become a best practice to use a multi-model approach, for example, looking at all possible variable combinations with something like a dredge approach. Those models would then be evaluated with something like an AIC. Equally concerning is the use of the spatial location, at least defined by region, as a covariate without first testing for spatial autocorrelation. Each of these three regions was selected because they represent a large proportion of the human population in Kazakhstan. Human populations by their nature are typically clustered in space meaning their covariates are likely autocorrelated. The authors here did nothing to test for spatial autocorrelation either in the input data or in the residuals of the models. Without such tests is difficult to assess whether or not the data for this study meet the assumptions of independence for the regression model selected. Likewise, it has become more usual to see a mixed model approach where a random effect would be used for region. These issues should be addressed and should not simply be addressed by adding one or two sentences to the methodology, but rather performing additional model evaluation, selection, and spatial autocorrelation testing.

Building on concerns about the regression model, the authors also used the T-test for the variables without first testing for normality. It may be more likely that a nonparametric test touches the Mann-Whitney U test may be more appropriate to analyze the same question.

Later in the results the authors state there were some adjustments for the models and those were not provided.

DISCUSSION: the discussion of the paper is well written. However the discussion highlights the results of the study, which do not address the concerns raised above about the methodology performed. It is important to ensure that the statistical analysis was appropriate before pacing and discussion that supports those results.

I think this is an interesting paper and addresses a very serious disease concern. The methodological comments I raise here can be addressed and should strengthen the paper.

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Reviewer #1: No

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Seroprevalence and risk factors for hepatitis B and hepatitis C in three large regions of Kazakhstan.

PONE-D-20-31835R1

Dear Dr. Issanov,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

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Kind regards,

Isabelle Chemin, PhD

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

The answers and improvment after the first round of review were convincing and the paper was improved to reach the desired quality to be published in PlosOne.

Reviewers' comments: