The Leading Transplantation Journals: A Trend Analysis, 2011–2021

Background As the field of transplantation has expanded, so have the quantity and variety of articles published on the topic. Evaluation of publications and journals is crucial to the expansion of transplant research. This study investigated the research output and journal metrics of the leading solid organ transplant journals published between 2011 and 2021 based on estimations of the trends in the category CiteScore from the Scopus database. Materials and Methods We obtained data on the listed journals from the Scopus Source List. We then filtered the list for “Transplantation” journals. Only the top quartiles or quartile 1 (Q1) journals were placed in this category. This study focused specifically on transplantation journals and did not include other journals related to diseases of transplanted organs such as the kidney, liver, heart, and lungs. Results The number of transplantation journals increased by 42.8% in the last ten years, from 28 in 2011 to 40 in 2021. Between 2011 and 2021, nine transplantation journals ranked in the highest quartile (Q1). The American Journal of Transplantation was the top journal in both years, with a 150% increase in citations and an 11.2% increase in articles published. Open access (OA) transplant journals rose from 3 in 2011 to 10 in 2021. In 2021, OA journals earned 8,555 citations, a 125% increase from 2011. Despite this increase, non-OA journals received more citations than OA in 2021 (p value 0.026). Conclusion Solid organ transplantation advances lead to more publications and citations. Regular journals and publications evaluation benefits academics and policymakers by promoting the growth of research. This study examined solid organ transplantation journals and gave a global perspective on transplant journal rankings and compared their status in 2011 and 2021.


Introduction
During the early twentieth century, a number of eminent researchers pioneered the concept of transplantation and the fundamental principles of transplantation immunology [1].Since then, the development of organ transplantation has become one of the great tales of medicine.Along with the other health professions and sciences, the feld of transplantation began to review its activities and accomplishments methodically.Te progression in the feld of transplantation was refected in the nature of research material to the point where there was an adequate awareness of the need for new journals that specialized in transplant subjects, which, since their establishment, have contributed to the advancement of the feld, a contribution accompanied by an increase in the number of publications and citations.
Te total number of journal articles and citations is considered an indicator in international scientifc rankings and a measure of a feld's academic productivity [2].Continual assessment of journals and publications is essential to the growth and maintenance of the research enterprise since it provides invaluable insight to researchers and policymakers.Te most prevalent journal-based metrics are CiteScore and Impact Factor (IF), both of which are crucial for determining how well a journal has performed over time [3].IF has grown in popularity as a metric of a journal's quality.However, the more recent metric, the CiteScore, provides a more comprehensive, transparent, and up-to-date representation of a journal's infuence than a single measure alone [3][4][5].
Te progress in academic performance of transplantation journals has rarely been studied.An objective and multiperspective evaluation of the academic performance of transplant journals might provide a complete understanding of the recent evolution of transplant scientifc studies.In this study, we assessed research output and journal metrics among top-performing solid organ transplant journals.We compared academic performance from 2011 to 2021 by using estimates for the trends in the category CiteScore from the Scopus database.Furthermore, we examined the open access (OA) status of transplant journals and the efect of that status on diferent journal indexes.

Methodology
We collected data on the included journals from the Scopus Source List on November 20, 2022, which is a list of journals and their respective metrics data since 2011.Journals are classifed into subfelds based on the aims and scope of the title and on the content they publish.
We fltered the list for "Transplantation" journals.Scopus classifes journals according to the All Science Journal Classifcation Codes (ASJC), a coding system that is provided by the Scopus database and is also summarized in Dataset [6].ASJC classifes journals into four main subject areas: health sciences, life sciences, physical sciences, and social sciences and humanities.Each subject area is also classifed into diferent subcategories.Te health sciences area is classifed into 29 subcategories, one of which is "Medicine," which is further classifed into 49 disciplines, including "Transplantation."We initially searched all solid organ transplant journals included in all quartiles, Q1, Q2, Q3, and Q4, and then included just the top quartiles, or quartile 1 (Q1) journals, which are defned as the frst position of the top 25% of journals in a certain subject, placed in this category.Nonsolid organ transplant journals, such as those specializing in bone marrow transplantation, were excluded.
For this study, we focused on evaluating transplant journals published between 2011 and 2021 using the Scopus database and the CiteScore metric.We did not evaluate and compare the impact factor (IF) based on the Web of Science database for several reasons.First, Scopus provides a larger database with broader coverage, as it indexes more journals than Web of Science [2].Tis wider coverage allows for a more comprehensive evaluation of the transplant journals.Second, Scopus has a more transparent calculation methodology for its CiteScore metric compared to the IF, making it a more reliable and easily verifable measure of journal performance [3,7].Furthermore, Scopus provides additional journal metrics such as the source normalized impact per paper (SNIP) and the SCImago journal rank (SJR), which can ofer a more well-rounded assessment of journal performance [2].By focusing on the Scopus database and its associated metrics, we aimed to provide a robust and transparent evaluation of the academic performance of transplant journals.OA Journals covered by Scopus are indicated as "Open Access" if the journal is listed in the Directory of Open Access Journals (DOAJ) and/or the Directory of Open Access Scholarly Resources (ROAD).

Statistical Analysis. We used IBM SPSS Statistics for
Windows, version 26.0 (IBM Corp., Armonk, N.Y., USA), in our analysis.We used the mean (±standard deviation) to describe continuous variables.We used to count (frequency) to describe other nominal variables.We performed an independent sample t-test to analyze the mean diference between O.A. and non-OA journals and between years with each continuous measurement (e.g., citation and document), and we presented the data in mean diference and standard deviation (±).We adopted a p value of 0.05 as a signifcant threshold.

Results
Te number of transplantation journals increased by 42.8% in the last ten years, from 28 1 and 2 show the top 25% quartile journals (Q1) in the feld of transplantation between the years 2011 and 2021.Tere were nine journals ranked as top-quartile journals in the feld of transplantation in 2011 and 2021.Te top journal was "American Journal of Transplantation" in both years, which had a 150% increase in the number of citations received, compared to only an 11.2% increase in the number of documents published.
Transplantation publishes the most articles with an average of 490 every year, followed by the American Journal of Transplantation with an average of 478 per year, as demonstrated in Figure 1, which depicts the average number of articles published per year by Q1 publications in 2021 since 2011.Te Clinical Kidney Journal and xenotransplantation have the lowest number of publications with 180 and 60 articles per year, respectively.
3.1.CiteScore Trend. Figure 2 shows the trend of the average CiteScore of all top-performing journals from 2011 to 2021.In 2011, the average CiteScore was 6.1, but it reached an alltime high of 8.8 in 2021.Table 3 shows the change in top quartile journals in the year 2011 and the new rank change in the year 2021, along with the change in the number of citations received (proportional relation) and documents published (inverse relation).Te drop in the number of citations received or the rise in the number of documents published without a matching rise in the number of citations would have a negative impact on the journal's ranking.

Open Access Journals.
Te number of transplant journals increased by 230% from 3 in 2011 to 10 in 2021.A total of 1,778 (mean 592.67 ± 38.07) documents were published in OA journals in 2011, compared to 3,022 (mean 302.2 ± 240.9) documents published in OA journals in 2021 (p � 0.104), representing a 70% increase in the quantity of documents.For citations, OA journals received 8555 citations in 2021, compared to 3801 in 2011, a 125% increase.Despite these improvements, the number of non-OA journals had signifcantly higher citations in 2021 compared to OA journals (p � 0.026), as shown in Table 4.

Discussion
Breakthroughs in the domains of immunology, immunosuppression, organ preservation, and surgical techniques led to increased research output and the necessity for journals devoted to the feld of transplantation.In 1966, the frst transplantation-specifc journal was established by the Transplantation Society and was named Transplantation [6].As the feld as a whole progressed, more specialized journals emerged, such as those for infectious disease related to transplantation (transplant infectious disease), pediatrics (pediatric transplantation), and xenograft transplantation (xenotransplantation).In our analysis, we observed an almost 40% increase in the number of transplantation journals between 2011 and 2021.Tis was also associated with an increase in the number of OA journals by 230% from 3 in 2011 to 10 in 2021.We observed that the top journals are still non-OA journals, and their citation indices increased, mostly driven by the articles published by the new journals.
Our fndings demonstrating an increase in citation frequency in transplantation journals are consistent with this overarching trend, which has been observed in all areas of medical research [8,9].Upon further examination of the data, specifcally focusing on Figures 2 and 3, an apparent rise in citations can be observed starting from the year 2016.Signifcantly, the implementation of machine perfusion in several solid organs has likely stimulated a substantial amount of scholarly investigation, resulting in a notable increase in the number of published academic articles [10,11].Te years 2020 and 2021 had an unparalleled increase, potentially linked to the abundance of papers related to COVID-19, which extensively occupied numerous journals, thus augmenting both the quantity and references of publications [12].
Nevertheless, it is important to make a crucial diferentiation: an increasing quantity of articles and citations does not necessarily indicate an improvement in the quality of research.Upon refecting on the environment of academic research a few decades ago, it becomes evident that there was a lower quantity of papers being published, while the ones that were produced tended to be more innovative and infuential in their respective felds.Contrarily, modern medical research, which includes transplants, frequently confrms or reiterates fndings from earlier studies, making genuinely original innovations scarce.Moreover, while OA has transformed academic publishing by making research more accessible, its article processing charge model has inadvertently paved the way for predatory journals.[13].Tese journals utilize the "pay-to-publish" model without maintaining academic standards [14].It is necessary to diferentiate between legitimate OA journals that adhere to rigorous academic standards and those that exploit the system.Researchers can identify and avoid predatory journals with the aid of the Directory of Open Access Journals (DOAJ) and guidelines from reputable organizations [15].Fortunately, none of the journals assessed in this study are representative of this problematic trend.
Tere is a growing consensus that a system to grade the quality of scientifc journals is essential, given the vast quantities of publications across all the major scientifc disciplines, and transplant journals are no exception.Scopus (Elsevier ® ) and Web of Science (Clarivate ® ) are two of the most prominent journal databases, and they established two methods to assist with the ranking of scientifc journals.CiteScore, which is a product that was introduced by Elsevier in order to compete with IF, which is a product that was  ® ) [3].

Journal of Transplantation
Te development of medical journals' academic performance has already been examined in a number of medical specialties [16][17][18][19][20] with the discipline of radiology demonstrating that all impact indices witnessed a modest increase between 2010 and 2019 [16].Another study found that the number of emergency medicine journals increased by 58% between 2000 and 2009 and that, since 2000, the impact indices for all emergency medicine journals have been trending upward [20].As with journals in other felds, transplant journals have strived to raise their impact measures by increasing the number of citations they obtain or the number of articles they publish.
Both the CiteScore and IF use the total number of publications and citations for their calculations [7,21].Te two metrics difer in that IF is less open about how it was calculated than the CiteScore [22].Te Journal IF has been deemed questionable because the calculations are "based on undisclosed data" despite the fact that the database has become more transparent recently [22,23].Even highimpact journals have criticized the quality of the data used to calculate the IF [4].In our study, we opted for CiteScore because it has several advantages over Impact Factor.CiteScore considers a broader range of document types, including articles, reviews, conference papers, and book chapters, resulting in a more comprehensive assessment of a journal's impact [2,24].In addition, CiteScore is based on a three-year citation window, which provides a more stable metric compared to the two-year window of Impact Factor [24].
Furthermore, CiteScore makes it possible for any Scopus subscriber to instantly access both the citing and cited documents [3].For example, CiteScore in 2020 counts the citations received in 2017-2020 for articles, reviews, conference papers, book chapters, and data papers published in 2017-2020 and divides this by the number of publications published in 2017-2020 [24].As a result, we believe that CiteScore ofers a better representation of a journal's performance.
CiteScore measures are included in the Scopus bundle of journal metrics, which also includes SNIP (Source Normalized Impact per Paper), SJR (SCImago Journal Rank), citation-and document-counts, and citation percentage [24].Many institutions rank journals with Scopus bibliometric indicators to evaluate the track record of scholars seeking hire or promotion; these metrics are also used to allocate fnancial bonuses or to evaluate funding applications [25].
As can be seen in Figure 3, the CireScore of the American Journal of Transplantation, the Clinical Journal of the American Society of Nephrology, Liver Transplantation, and the Clinical Kidney Journal have all been on an upward trajectory every year since 2016.Xenotransplantation entered the Q1 club in 2016 with a CireScore of 6.4, and it has been there ever since, with a CireScore of 6.1 in 2021.In the 2021 list, Transplantation Review, Transplant International, and Current Opinion in Organ Transplantation were substituted for Transplantation and Cellular Terapy, Clinical Kidney Journal, and Xenotransplantation.
In contrast to the old paradigm of scientifc publishing, which required users to pay to access articles, OA publication is a relatively new phenomenon in the research community and represents a form of development in a feld [17].OA has revolutionized scientifc publishing by making research available to more readers [17,26].OA articles are published more quickly and can be shared online, accelerating the availability of new knowledge and the pace of scientifc research [17,27].
According to numerous studies conducted in a wide variety of medical felds, OA medical journals have significantly higher CiteScores, percent cited articles, and SNIP compared to non-OA journals [17,26,28,29].However, for the feld of transplant our analysis revealed that, in 2021, subscription journals signifcantly outperformed OA transplant journals in terms of citations (p value 0.026); number of articles; CireScore; SNIP; and SJR.Te dominance of the subscription journal in the transplantation feld may be due to the preference of authors with unique and infuential (i.e., more citable) outcomes to submit their fndings to prestigious, mostly subscription-based journals.Although the number of OA transplant journals tripled between the years 2011 and 2021, our fndings showed that eight of the top nine Q1 transplant journals in the Scopus ranking are paid-only journals that require a subscription to access.Te Clinical Kidney Journal was the only OA journal  It is important to note that articles in the feld are also published in nonspecialty journals.We used the Scopus database for our analysis, as it is the most inclusive, highquality database [2].However, other databases may provide additional information on the feld and should be considered in future research.

. Conclusion
Te increase in the number of articles and citations in the feld of transplantation and the rise in the number of specialized journals refect the progress established in the feld.Evaluation of journals and publications on a regular basis is crucial to the growth and maintenance of research enterprises because of the invaluable insight it provides to academics and policymakers.Tis study analyzed journals that specialize in solid organ transplantation and provided a comprehensive overview of their development.It provided a global perspective on the advancement of transplant journal rankings and compared the status of the journals in 2011 and 2021.

Table 1 :
Top quartile (Q1) journals in 2011.Journal Open access CiteScore Citations *From the total number for the period of 2008-2011.4Journal of Transplantation

Figure 1 :
Figure 1: Mean number of articles published per year by Q1 journals in 2021 since 2011.

Figure 2 :
Figure 2: Mean CiteScore trend for the top quartile journals in 2021 since 2011.

Figure 3 :
Figure 3: CiteScore trend of the American Journal of Transplantation, Clinical Journal of the American Society of Nephrology, Liver Transplantation and Clinical Kidney Journal since 2011.
in 2011 to 40 in 2021.Te yearly 2 Journal of Transplantation average number of articles published by the existing 28 journals in 2011 was 643.82 (±850.18).Tis is compared to the yearly mean article published by the existing 40 journals in 2021, 465.07 (±521.49), a diference that was not statistically signifcant (p � 0.287).Te number of citations received in 2011 was 82,877 (mean: 2959.89 ± 4331.44) citations, while the number of citations received in 2021 was 95,130 (mean: 2378.25 ± 3862.07) citations, a 14.8% increase from 2011, with a nonstatistically signifcant diference (p value of 0.563).Tables

Table 4 :
Comparison between open access (OA) and non-OA journals in 2021 ranking.