Introduction and background
Kidney transplantation is a crucial procedure for patients with end-stage renal disease (ESRD) that provides a survival advantage over maintenance on dialysis [1]. The field of kidney transplantation has undergone substantial advancements in surgical techniques, immunosuppression, and patient outcomes. Major developments in transplantation and immunology have expanded the pool of acceptable donors and recipients, while improved organ matching and preservation, combined with the advancements in surgical protocols and chemoprophylaxis, have all contributed to improved clinical outcomes [2,3].
Evaluative bibliometrics is a branch of quantitative science that measures the efficacy of a study using techniques such as citation analysis [4]. The frequency with which an article has been cited allows us to measure the effect of an article over time. Highly cited articles demonstrated the importance of the subjects discussed in these articles among the scientific community of the relevant medical discipline. Bibliometric analysis can be helpful in providing an overview of the publications that have the most influence in certain areas of medical practice, as well as providing an idea of the most influential institutions and authors to stimulate collaborations [5].
Furthermore, bibliometric analysis is a valuable tool for evaluating the impact and trends in a specific field of research [6]. In the context of kidney transplantation, the analysis of the top 100 cited articles provides valuable insights into the most influential studies and authors in this field [7,8].
To determine the top 100 kidney transplantation articles cited most frequently across all journals, we used bibliometric analysis. In this analysis, we focused on authors, annual trends, journals, and countries to gain insights into the most influential and impactful research in the field.
Review
Materials and methods
Data Collection and Retrieval Methods
We searched the Scopus database using the terms "kidney" and "renal," as well as transplant-related words such as "transplant," "donor," "recipient," and "procurement." The terms were searched in the title/abstract. The exact algorithm was as follows: TITLE-ABS-KEY ("kidney transplant" OR "renal transplant" OR "kidney donor" OR "renal donor" OR "kidney recipient*" OR "kidney procurement"). All articles up to the query date on December 21, 2022, were included. Additionally, we included all document types, such as articles, reviews, conference papers, editorials, book chapters, and meeting abstracts. Articles unrelated to the field of transplantation were excluded. Articles with missing information were manually removed from the spreadsheet. All included articles were in the English language. A list of the top 100 cited articles was created.
Data Analysis
All analyses were citation count-based. We analyzed authors, annual trends, journals, and countries. Tables and figures were generated using VOSviewer version 1.6.18 and Microsoft Excel from Office 365 (Microsoft Corp., Redmond, WA, USA). A flowchart was structured to demonstrate included/excluded results. Continuous data were reported as mean ± standard deviation (SD), while frequencies were reported as numbers (n). We compared mean citations between different subgroups using the analysis of variance (ANOVA) test; in case of violating the ANOVA test assumptions, we used the nonparametric Kruskal-Wallis test. A p-value of 0.05 or less was deemed statistically significant. All statistical analyses were done using R statistical language (Vienna, Austria).
Results
Up to the search date, a total of 68,271 published articles were related to kidney transplantation in the Scopus database. The top 100 cited papers were included, but one study was excluded due to being psychiatry-related. As for the document type, 92 studies were articles, five studies were reviews, two were conference papers, and one study was editorial (Figure 1). The 100 articles have cited a total of 76,029 times, with a mean ± SD of 760.3 ± 284.6.
Figure 1
Flowchart of search results and types of included documents
Over 910 authors were included in our analysis, 83 of which were the first authors on at least one document. When the first authors on the documents were assessed, Kasiske B.L. was the first author of five articles accounting for 3,122 citations. Opelz G. appeared on four documents with 2,948 citations. Vincenti F., Ojo A.O., and Meier-Kriesche H.-U. each were the first authors of three documents (n = 2,281, 2,204, and 2,093, respectively). Table 1 demonstrates a list of the top cited authors from the included studies.
Table 1
First authors of the 100 most cited articles in the field of kidney transplantation
*The authors' total number of citations within the included top 100 articles
KDIGO: Kidney Disease: Improving Global Outcomes, CKD-MBD: chronic kidney disease-mineral and bone disorder
| ID | Name | Number of documents | Total citations* |
| 1 | Kasiske B.L. | 4 | 3,122 |
| 2 | Opelz G. | 4 | 2,948 |
| 3 | Vincenti F. | 3 | 2,281 |
| 4 | Ojo A.O. | 3 | 2,204 |
| 5 | Meier-Kriesche H.-U. | 3 | 2,093 |
| 6 | Hariharan S. | 2 | 2,232 |
| 7 | Terasaki P.I. | 2 | 1,984 |
| 8 | Hirsch H.H. | 2 | 1,779 |
| 9 | Port F.K. | 2 | 1,235 |
| 10 | Brennan D.C. | 2 | 1,140 |
| 11 | KDIGO CKD-MBD Work Group | 1 | 2,053 |
| 12 | KDIGO Transplant Work Group | 1 | 1,783 |
| 13 | Nankivell B.J. | 1 | 1,653 |
| 14 | Ekberg H. | 1 | 1,422 |
| 15 | Cho S. | 1 | 1,286 |
| 16 | Solez K. | 1 | 1,285 |
| 17 | Sellarés J. | 1 | 1,065 |
| 18 | Pappas P.G. | 1 | 1,035 |
| 19 | Kamar N. | 1 | 1,024 |
| 20 | Pirsch J.D. | 1 | 1,019 |
| 21 | Fioretto P. | 1 | 1,011 |
| 22 | Engels E.A. | 1 | 969 |
| 23 | Kestenbaum B. | 1 | 945 |
| 24 | Nortier J.L. | 1 | 923 |
| 25 | Rule A.D. | 1 | 906 |
| 26 | Ratner L.E. | 1 | 869 |
| 27 | Groth C.G. | 1 | 854 |
| 28 | Kawai T. | 1 | 850 |
| 29 | Stallone G. | 1 | 819 |
| 30 | Ibrahim H.N. | 1 | 816 |
| 31 | Herzog C.A. | 1 | 801 |
| 32 | Holdaas H. | 1 | 793 |
| 33 | Perico N. | 1 | 757 |
| 34 | Hirsch J.S. | 1 | 753 |
| 35 | Moers C. | 1 | 742 |
| 36 | Uchino S. | 1 | 729 |
| 37 | Bullingham R.E.S. | 1 | 718 |
| 38 | Wiebe C. | 1 | 713 |
| 39 | Ortho Multicenter Transplant Study Group | 1 | 710 |
| 40 | Jensen P. | 1 | 707 |
| 41 | Kootstra G. | 1 | 692 |
| 42 | Noris M. | 1 | 686 |
| 43 | Lown K.S. | 1 | 680 |
| 44 | Lamb K.E. | 1 | 672 |
| 45 | Dragun D. | 1 | 670 |
| 46 | Nashan B. | 1 | 669 |
| 47 | Rao P.S. | 1 | 666 |
| 48 | Muzaale A.D. | 1 | 657 |
| 49 | Mcmurray J.J.V. | 1 | 654 |
| 50 | Loupy A. | 1 | 637 |
| 51 | Almond P.S. | 1 | 636 |
| 52 | Mayer A.D. | 1 | 633 |
| 53 | Lefaucheur C. | 1 | 620 |
| 54 | Hesselink D.A. | 1 | 617 |
| 55 | El-Zoghby Z.M. | 1 | 611 |
| 56 | Schortgen F. | 1 | 599 |
| 57 | Poggio E.D. | 1 | 593 |
| 58 | Changelian P.S. | 1 | 588 |
| 59 | Czock D. | 1 | 585 |
| 60 | Macdonald A.S. | 1 | 581 |
| 61 | Poulsom R. | 1 | 581 |
| 62 | Najarian J.S. | 1 | 561 |
| 63 | Newell K.A. | 1 | 552 |
| 64 | Kauffman H.M. | 1 | 549 |
| 65 | Reeve C.E. | 1 | 549 |
| 66 | Segev D.L. | 1 | 548 |
| 67 | Palacios G. | 1 | 544 |
| 68 | Vo A.A. | 1 | 544 |
| 69 | Merion R.M. | 1 | 543 |
| 70 | Barton F.B. | 1 | 540 |
| 71 | Mjøen G. | 1 | 537 |
| 72 | Einecke G. | 1 | 531 |
| 73 | Yarlagadda S.G. | 1 | 531 |
| 74 | Kronbach T. | 1 | 529 |
| 75 | Laterza O.F. | 1 | 521 |
| 76 | Montgomery R.A. | 1 | 521 |
| 77 | Birkeland S.A. | 1 | 517 |
| 78 | Hoover R. | 1 | 516 |
| 79 | Kinlen L.J. | 1 | 515 |
| 80 | Metzger R.A. | 1 | 512 |
| 81 | Yamada K. | 1 | 510 |
| 82 | Pereira M.R. | 1 | 503 |
| 83 | Ketteler M. | 1 | 501 |
The most frequently published journals were the New England Journal of Medicine (n = 22), Transplantation (n = 14), and the American Journal of Transplantation (n = 14). The New England Journal of Medicine had the highest number of citations (n = 19,528), followed by the American Journal of Transplantation (n = 11,392) and then Transplantation (n = 10,482) (Table 2). Figure 2 visualizes the most cited journals and the interconnections between them.
Table 2
Bivariate analysis of mean citations by article's characteristics
SD: standard deviation
| Subgroup | Number | Total number of citations | Total number of citations (mean ± SD) | p-value | |
| Article year | <2000 | 30 | 22,740 | 585.7 ± 215.1 | 0.468 |
| 2000-2005 | 37 | 27,501 | 743.3 ± 266.9 | ||
| 2006-2010 | 21 | 17,587 | 837.5 ± 422.1 | ||
| 2011-2015 | 9 | 6,444 | 716 ± 181.8 | ||
| 2016-2020 | 3 | 1,757 | 628 ± 144.9 | ||
| Authors' country | United States | 57 | 41,066 | 720.5 ± 217.9 | 0.139 |
| Germany | 8 | 5,373 | 671.6 ± 149.9 | ||
| Canada | 6 | 4,724 | 787.3 ± 314.8 | ||
| United Kingdom | 4 | 2,383 | 595.8 ± 62 | ||
| France | 4 | 2,880 | 720 ± 203.3 | ||
| Italy | 4 | 3,273 | 818.3 ± 139.5 | ||
| Norway | 3 | 2,037 | 679 ± 130.3 | ||
| Netherlands | 3 | 2,051 | 683.7 ± 62.9 | ||
| Switzerland | 3 | 2,308 | 769.3 ± 225 | ||
| Sweden | 2 | 2,276 | 1,138 ± 401.6 | ||
| Global | 2 | 3,836 | 1,918 ± 190.9 | ||
| Australia | 1 | 1,653 | - | ||
| Belgium | 1 | 923 | - | ||
| Denmark | 1 | 517 | - | ||
| Japan | 1 | 729 | - | ||
| Document type | Article | 92 | 70,583 | 767.2 ± 293.19 | 0.790 |
| Review | 5 | 3,588 | 717.6 ± 163.3 | ||
| Conference paper | 2 | 1,204 | 602 ± 127.3 | ||
| Editorial | 1 | 654 | - | ||
| Journals | New England Journal of Medicine | 22 | 19,528 | 887.6 ± 318.6 | 0.172 |
| American Journal of Transplantation | 14 | 11,392 | 813.7 ± 340.3 | ||
| Transplantation | 14 | 10,482 | 748.7 ± 212.5 | ||
| Kidney International | 8 | 5,428 | 678.5 ± 260 | ||
| Lancet | 7 | 4,506 | 643.7 ± 101.6 | ||
| Journal of the American Society of Nephrology | 6 | 4,061 | 676.8 ± 137.1 | ||
| JAMA | 5 | 3,328 | 665.6 ± 176 | ||
| Clinical Pharmacology and Therapeutics | 3 | 1,826 | 608.7 ± 75.8 | ||
| Clinical Pharmacokinetics | 2 | 1,303 | 651.5 ± 94 | ||
| Kidney International Supplements | 2 | 2.707 | 1,353.5 ± 989.2 | ||
| Transplantation Proceedings | 2 | 1,629 | 814.5 ± 173.2 | ||
| American Journal of Clinical Pathology | 1 | 921 | - | ||
| Annals of Internal Medicine | 1 | 906 | - | ||
| British Medical Journal | 1 | 515 | - | ||
| Clinical Chemistry | 1 | 521 | - | ||
| Clinical Infectious Diseases | 1 | 1,035 | - | ||
| Clinical Journal of the American Society of Nephrology | 1 | 686 | - | ||
| Critical Care Medicine | 1 | 729 | - | ||
| Diabetes Care | 1 | 540 | - | ||
| International Journal of Cancer | 1 | 517 | - | ||
| Journal of Clinical Investigation | 1 | 552 | - | ||
| Journal of Pathology | 1 | 581 | - | ||
| Journal of the American Academy of Dermatology | 1 | 707 | - | ||
| Nature Medicine | 1 | 510 | - | ||
| Nephrology Dialysis Transplantation | 1 | 531 | - | ||
| Science | 1 | 588 | - |
Figure 2
Visualization of the most cited journals
The first authors' institutes were assessed, 57 of which were from the United States with the highest citations (n = 41,066). The second most frequent country was Germany (n = 8) with 5,373 citations, followed by Canada (n = 6) with 4,724 citations (Figure 3).
Figure 3
Visualization of authors' countries
The greatest number of articles were published from 2000 to 2005 (n = 37). Thirty articles were published before the year 2000, and 21 articles were published from 2006 to 2010. Accordingly, most citations were from 2000 to 2005 (n = 27,501), followed by the period before the year 2000 (n = 22,740).
Analysis of the top 100 most cited articles according to year revealed that there was no significant difference in mean citations between year groups (p = 0.468). Furthermore, no significant differences were found between authors' countries, document types, or journals in terms of the mean number of citations (p = 0.139, 0.790, and 0.172, respectively) (Table 2).
The top 100 cited articles in the kidney transplantation field are shown in the Appendices. “KDIGO clinical practice guidelines for the prevention, diagnosis, evaluation, and treatment of Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD)” published by the Kidney Disease: Improving Global Outcomes “Chronic Kidney Disease-Mineral and Bone Disorder “ (KDIGO CKD-MBD) Work Group, which was published in the Kidney International Supplements journal, was the most cited study (n = 2,053) [9], followed by a guideline paper published in the American Journal of Transplantation, also done by the KDIGO Work Group (n = 1,783) [10]. The least cited article had 501 citations published by Ketteler et al. [11] in Kidney International.
Discussion
Bibliometric analysis and visualization tools, such as VOSviewer, have gained prominence for their ability to assess and present complex citation patterns and research trends in various fields [12]. These tools enable researchers, clinicians, and decision-makers to identify influential publications, emerging research topics, and leading contributors within the domain [13,14]. The field of kidney transplantation has seen significant advancements in recent years, leading to improved long-term allografts and patient survival. The introduction of cyclosporine in 1983 marked a major turning point in the history of solid-organ transplantation, significantly reducing the risk of rejection and leading to a proportional increase in one-year patient and graft survival rate for a kidney transplantation to over 90% [3,15].
A previous bibliometric analysis of the most-cited kidney transplantation papers made use of the Web of Science database, covering articles up to 2019 [16]. In contrast, our study employs the Scopus database and encompasses a more diverse range of document types, resulting in a broader and more current assessment of kidney transplantation literature. By including articles, reviews, conference papers, editorials, book chapters, and meeting abstracts through December 21, 2022, our research captures the latest and most influential publications in the field. Furthermore, our study delves deeper into the relationships between citations and factors such as publication year, authors' countries, document types, and journals, shedding light on emerging trends and citation patterns within kidney transplantation research. This comprehensive approach provides valuable insights that were not present in the earlier study, making our analysis a superior resource for researchers, clinicians, and decision-makers in the field of kidney transplantation.
Kidney transplantation had more publications than any other organ transplantation specialty [17]. The top 100 cited articles provide a snapshot of the most influential and impactful research in the field. The results show that the most cited article was a clinical practice guideline paper published by the Kidney Disease: Improving Global Outcomes (KDIGO) Work Group, which highlights the importance of guidelines and best practices in the field of kidney transplantation. The findings also indicate that the most productive authors were primarily from the United States, with the most frequently cited first author being Kasiske B.L. The top cited journals were the New England Journal of Medicine, Transplantation, and the American Journal of Transplantation, which suggests that these journals are at the forefront of research in the field of kidney transplantation. It is worth noting that the greatest number of articles and citations were published between 2000 and 2005, which suggests that there has been a significant increase in research in the field of kidney transplantation over the past two decades. However, the results also showed that there was no significant difference in mean citations between year groups, authors' countries, document types, or journals. This suggests that while the field of kidney transplantation has seen significant progress, there is still room for improvement, and further research is needed to advance the field.
Conclusions
This bibliometric analysis provides valuable insights into the current state of research in the field of kidney transplantation. The results highlight the most influential and impactful research in the field, as well as the most productive authors, journals, and countries. The findings of this study can be used to guide future research and support decision-making in funding and policy.
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