The Open Dermatology Analysis of Publication Activity and Research Trends in the Field of Lichen Planus: Pubmed Review

Structuredsummary 2 Background: Currently, there is only one bibliometric study of lichen planus (LP) and oral lichen planus (OLP) in the literature, which examined the most cited articles in the Scopus database. Our study covered all published articles for 140 years since 1880 to 2021 in the PubMed database. In addition to the classical bibliometric analysis, we conducted a lexical analysis of key terms in order to build research trends in the field of oral lichen planus. Aims: Analysis of publication activity in the field of lichen planus by countries, their economic status and population, as well as identification of concomitant diseases by lexical analysis of key terms extracted from headings and abstracts over the past 20 years. Methods: Information from the PubMed database was retrieved automatically based on a query for the period from 1880 to 2021 including the fields: title, abstract, authors, and year of publication. A total of 8173 articles were retrieved. The selection of keywords and the identification of trends in related terminology were carried out using a combination of expert and automatic methods. An analysis of publication activity by country and by socio-economic indicators was carried out. With the help of neural network analysis the most characteristic terms related to LP were identified. Common terms were ranked by occurrence in titles and abstracts. Results: Publication activity in the field of LP and OLP has especially increased in the 21st century. The United States is the most productive country. China is a leader among countries with economies in transition. India is a leader among emerging economies. LP research is distributed worldwide. Finland ranks first in the number of publications per capita. The temporal dynamics of terminology is noted including an increase in the number of terms used in any field of science (hereinafter referred to as general scientific terms). Conclusion: Publication activity in the field of LP and OLP has increased significantly in the 21st century. The highest publication activity was observed among authors from India, the USA and China. The leaders among economically developed countries are Italy, among the countries with economies in transition - China, and among the emerging economies - India. Based on lexical analysis of key terms the following concomitant diseases were identified: carcinoma, leukoplakia, hepatitis, lupus.


Rationale
3 This study presents the analysis of the researchers' performance in the field of lichen planus (LP). The data were extracted from the PubMed database with the search by parameters: relative growth rate, country-wise distribution, and prevailing vocabulary. Lichen planus is a chronic inflammatory, immune-dependent disease of the skin and mucous membranes. In general structure of dermatological morbidity, LP is 1.5-2.4%, among all diseases of the oral mucosa -30-35%. Despite the prevalence, only one bibliometric analysis related to LP in the academic literature has been carried out. Study selection 9 Selection of articles with the term "lichen planus", breaking them down over the years. 5 Data collection process 10 The process includes two steps. The first step uses semantic selection of appropriate terms with a short context size (with the 3 words window). Next, a semantic information is used to select the prevalent terms by year.

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Data items 11 We proceeded from the assumption that the joint use of terms indicates their joint study.

Analysis of Publication Activity and Research Trends
The Open Dermatology Journal, 2022, Volume 16 3 Section/topic # Checklist item Reported on page #

Study characteristics
18 The data for our study were extracted from the PubMed database. The following search keywords were used (search query fragment): "lichen planus" OR "lichen planus pigmentosus" OR "hypertrophic lichen planus" OR " mucosal lichen planus" OR "annular lichen planus" OR "hypertrophic lichen planus" OR "atrophic lichen planus" OR "ulcerative lichen planus" OR "bullous lichen planus" OR "lichen planus pemphigoides" OR "inverse lichen planus" OR "actinic lichen planus". We analyzed articles published from 1880 to 2021. A total of 8173 records for LP and 4775 records for OLP were extracted from PubMed database for this study (15.01.2021). The papers from different countries were identified by using the Advanced Search Builder. The number of publications by country was determined by inserting the name/s of the countries in the «affiliation» field in the «advanced» section of the PubMed search engine, for example, (

Summary of evidence
24 A comparative analysis of publication activity over the decades showed that more than 62% of the total number of publications was published in less than 20 years of the 21st century.
In the most productive 20 countries in LP research, India stands out in the first place with 17,11% of the total number of publications. LP has a worldwide distribution with no overt racial predisposition. We investigated whether the Gross Domestic Product (GDP) influences LP research productivity in all countries by economic groups according to the classification of the International Monetary Fund. The leaders among the economically developed countries are Italy, USA, UK, Spain, Japan. Among the countries with economies in transition, China is the undisputed leader. Among the emerging economies, the leaders are India, Iran and Brazil. Countries with economies in transition and countries of the former USSR either do not have publications at all or have very few. A statistical analysis of the headings and abstracts of articles related to LP made it possible to distinguish the following lexical and semantic groups. The total number of words selected in 1960-1979 was 664, in 1980-1999 -4413, 2000-2020 -11168. In each reviewed period, the titles were dominated by specific medical terms (related to the disease). In each period, general scientific terms were in the second place in use, and general medical terms were in the third place. However, the dynamics of the correlation of terms is noted.
Limitations 25 The study was limited to English-language publications Section/topic # Checklist item Reported on page #

Conclusions 26
The bibliometric analysis of publications in the field of lichen planus was performed for the period 1880-2020. It is shown that publication activity has increased significantly in the 21st century. At the same time, the growth of publications related to OLP is faster. We have identified the most active 20 countries by the number of publications per 1 million people. The analysis of the dependence of publication scientific activity on the GDP of countries was carried out. The article contains lexical analysis of key terms, statistical processing of a variety of terms, and the definition of thematic groups of terms. Based on the analysis of publication activity, terminological trends were calculated for the period from 1960-2020, and the correlation between the most popular areas of research in the field of lichen planus was determined. Recently, special attention has been paid to the problem associated with lichen planus and other diseases such as carcinoma and leukoplakia, which may be a topic for further deeper studies. The growth is noted for publications related to carcinoma and LP, and notably for carcinoma and OLP.