A bibliometric analysis of the global research on sofosbuvir

In this article, we examine the research on sofosbuvir with a bibliometric analysis of global research production. The study of sofosbuvir has been a field of intense research in the past few years, with Latin American contributions playing a modest role. With continued drug development and approval of hepatitis C antivirals, research is expected to increase. Our findings will assist scholars and policy makers in their efforts to improve scientific research policies, with the goal of maximizing the access to treatments, especially in low and middle-income countries.


Introduction
Hepatitis C virus (HCV) has a major impact on public health, with around 170 million people in the world being affected 1 . In Latin America, the prevalence of hepatitis C has been estimated to be at around 1.6% of the adult population, and the most common genotypes are 1 and 3 2,3 . The new treatments for HCV include direct-acting antivirals (DAAs), which shorten length of therapy, improve sustained virologic response rates, and minimize side effects 4 .
Sofosbuvir is one of the most important DAAs in the market today, but high prices have led to a large increase in spending by health systems and can be a barrier to rapid global treatment, especially in low and middle-income countries 5 . The identification of global research on DAAs might lead to new insights into the treatments of HCV and suggest research directions.
Based on the above, our study aimed to identify and explore the worldwide development of sofosbuvir research.

Methods
We performed a bibliometric analysis using the original articles indexed in Web of Science. The search strategy used the following MeSH and non-MeSH terms in the title field: Sofosbuvir, Sovaldi, PSI 7977, and GS 7977. The validity of the search strategy was tested by manually reviewing retrieved articles. Bibliometric indicators were investigated by analyzing annual research output, languages, countries, journals, authors, institutions, and citations. Indicators were analyzed with the option "Analyze Results" and "Create Citation Report" in Web of Science. Author co-citation analysis (ACA) was presented as network visualization map using VOSviewer (version 1.6.4) techniques 6 .

Results
A total of 341 publications for the period of 2010-2017 (up to March 31, 2017) were retrieved and assessed. There were a total of 126 journals that published research on sofosbuvir. Twentyfour articles were economics-based. The three most prolific journals were Hepatology (31 articles), Gastroenterology (17), and Journal of Hepatology (17), responsible for 19.1% of the total publication output. The retrieved documents were published by 46 different countries. The largest contributors in absolute number of articles were USA (220), France (47), and Germany

Conclusions
According to our bibliometric analysis, the study of sofosbuvir has been a field of intense research in the past few years. Developed countries have had an enormous impact on the global research in the field. Recently, interest has focused on the use of sofosbuvir to treat Zika infection, and an important contribution to the body of sofosbuvir research has been supported by its manufacturer. With continued drug development and approval of hepatitis C antivirals, research is expected to continue increasing.

Competing interests
No competing interests were disclosed.

Grant information
The author(s) declared that no grants were involved in supporting this work. As sofosbuvir became an antiviral of major interest, not only towards HCV and ZIKV, but also for Dengue virus (DENV) ( ) -my suggestion is to compare https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5524696/ the studies on the pharmacology of this drug on HCV and Flavivirus members. The study on ZIKV and sofosbuvir cited in this manuscript ( ) was preceded by a https://www.nature.com/articles/srep40920 pre-print, which was the first contribution to open the field of sofosbuvir against flaviviruses ( https://www.biorxiv.org/content/early/2016/07/06/061671; https://www.the-scientist.com/?articles.view/articleNo/46585/title/Sofosbuvir-Shows-Anti-Zika-Activity-In-Vitro/ ) -around six months after the ZIKV outbreak. I presume that the proposed comparison will demonstrate the installed capacity of response to novel (re)emergent viruses in Latin America.

If applicable, is the statistical analysis and its interpretation appropriate? Not applicable
Are all the source data underlying the results available to ensure full reproducibility? Yes What were the bibliometric parameters that you analyzed? I cannot see any description of how did you analyse the data gathered. How did you reach to agreement to include or not to include an article? Did you calculate the degree of agreement between researchers?

This section needs a lot of work
The results should mirror the subtitles under methods Provide results for each subitem in the bibliometric analysis you did. The assessment is superficial and more in depth analysis is needed. Use subtitles You may create 2-3 tables summarizing key findings/analysis. What does Figure 1 mean?

Conclusions
What are the main gaps? What are the possibilities for future research?

Are sufficient details of methods and analysis provided to allow replication by others? Partly
If applicable, is the statistical analysis and its interpretation appropriate?

Not applicable
Are all the source data underlying the results available to ensure full reproducibility? Yes

Are the conclusions drawn adequately supported by the results? Partly
No competing interests were disclosed.

I have read this submission. I believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.
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