Research on the global trends of COVID-19 associated acute kidney injury: an updated bibliometric analysis

Dear Editor:

We recently read the study by Zhao et al. entitled “Research on the global trends of COVID-19 associated acute kidney injury: a bibliometric analysis” [1]. This analysis delves into the evolving research landscape surrounding COVID-19-related acute kidney injury (AKI), serving as a pivotal reference for ongoing investigations into the mechanisms and treatments of COVID-19 AKI. While the insights provided are invaluable, we suggest an enhancement of the information retrieval techniques to augment the breadth and accuracy of future studies. Additionally, we recommend the inclusion of the H-index, a critical measure of a researcher’s scholarly influence and output [2]. Projecting future publication trends is also advisable, as it enables the academic and research communities to anticipate shifts, optimize resource allocation, and align with broader societal and scientific objectives.

The research on AKI is inherently multidisciplinary, covering various fields, with a primary focus on medical and bioscience literature. To ensure that no relevant studies are missed, we opted to use the Web of Science Core Collection (WOSCC), which includes multiple sub-databases. This strategy allows for a comprehensive retrieval of relevant literature from medical and biosciences, while also capturing any multidisciplinary studies that could provide additional insights into COVID-19-associated AKI. However, our focus remains on the most relevant literature, and by using WOSCC, we ensure a broad yet focused review of the available studies. Limiting the search to a single sub-database, such as SCI-EXPANDED, might exclude some pertinent studies, which is why we considered the full range of sub-databases within WOSCC [3].

An essential aspect of bibliometric research is the creation of accurate search terms and strategies. Zhao et al. implemented a Topic Search (TS) that encompassed terms from “Title (TI)”, “Abstract (AB)”, “Author Keywords (AK)”, and “Keywords Plus (KP)”. However, “KP” terms are generated by WoSCC’s algorithms and may include unrelated publications. Our research indicates that concentrating exclusively on “TI”, “AB”, and “AK” enhances the precision and relevance of the collected data [4]. We futher refined these search terms, leading to more accurate data acquisition in our study. The revised search strategy is detailed in Table S1.

The H-index is a crucial metric for evaluating the quantity and quality of a researcher’s academic contributions. It is defined as the number of a scholar’s publications (H) that have each been cited at least H times, highlighting the impact of their most significant works [2]. As a robust indicator of academic influence, the H-index reflects research that garners substantial recognition and citations. Researchers’ H-indices were calculated using the Web of Science online platform (https://webofscience.clarivate.cn/). This metric is essential for academic evaluations, career advancement, and institutional rankings, offering a balanced measure of both productivity and influence.

Using an updated search method, we gathered 3,210 papers published between January 1, 2020, and December 31, 2023, conducting the search on August 4, 2024. After filtering out irrelevant records, including meeting abstracts, editorial materials, letters, and other non-peer-reviewed content, we analyzed a total of 2,806 papers. This filtering process helped ensure that only relevant and high-quality studies were included in the analysis. Figure 1a shows the annual publication distribution. Our analysis revealed a spike in COVID-19 AKI research in 2021, demonstrating significant interest. Interestingly, publications have decreased each year since 2022. We estimate publication counts of 616 for 2024, 583 for 2025, and 550 for 2026. The data show a slight rise in publications in 2024, but the overall trend of COVID-19-associated AKI research continues to decline in the following years. Figure 1b–f illustrate the geographic distribution of corresponding authors and the international collaboration networks among countries, institutions, and journals. The United States, followed by China and Italy, are the top contributors (Figure 1c).

Figure 1.

A bibliometric analysis of COVID-2019 AKI. (a) The annual publication trends over the past four years are depicted, with a red line representing a linear regression of publication numbers against years (Y = -32.6X + 66598.4, R² = 0.0422; X-axis represents the year, Y-axis represents annual publications). (b) a geospatial map illustrates the distribution of corresponding authors by country. (c-d) VOSviewer visualizations depict networks of international collaborations among various countries and institutions. (e) The top 10 authors in the field of COVID-2019 AKI are highlighted, with the number of publications and H-index shown in parentheses (left and right, respectively). (f-g) visualizations demonstrate the networks of international collaborations among different journals and manuscript citations. Node size and color indicate the quantity and category, respectively, while connecting lines denote levels of collaboration or co-citation. (h) a keyword density map is shown, where the transition from cool to warm colors indicates an increase in keyword frequency. (i) a list of the top 20 references with the most significant citation bursts is provided. (j) The top 20 keywords with the most significant citation bursts are identified.

Figure 1d underscores the institutional collaborations, both domestic and international. The leading institutions include Huazhong University of Science and Technology, Harvard Medical School, and Icahn School of Medicine at Mount Sinai. Ronco, Claudio is identified as the most productive author with 16 publications and an H-index of 10, highlighting his significant contributions (Figure 1e). Although Jhaveri, Kenar D. has fewer publications, with only 9 articles, his H-index of 8 reflects high impact and frequent citations. “Cureus Journal of Medical Science” leads in publication volume (Figure 1f). Our bibliographic coupling analysis identifies Zhou et al.’s work as the most cited [5] (Figure 1g), which details the clinical progression and mortality risk factors for adult inpatients with COVID-19 in Wuhan, China, noting that AKI typically developed about 15 days (range 13.0–19.5) after symptom onset across all patients, and in survivors, it appeared on day 9. The most recurrent keywords are showcased in a keyword density map in Figure 1h, with “COVID-2019” as the most prevalent term, followed by AKI, acute respiratory distress syndrome (ARDS), and mortality. These keywords underscore the connection between COVID-19 and both AKI and ARDS, which significantly elevate mortality risk. Additionally, Figure 1i highlights the top 20 references with notable citation bursts, providing insights into pivotal studies in this domain. Figure 1j displays the top 20 keywords with notable citation bursts, particularly highlighting those with bursts continuing through 2024. These include chemotherapy, IgA nephropathy, immunotherapy, patient, COVID-19 vaccine, gross hematuria, tumor microenvironment, vaccination, mutations, mechanisms, glomerular filtration rate, relapse, cystatin c, antibody, and illness. These terms reflect ongoing research into critical areas such as immune responses, kidney function, and therapeutic strategies, offering insights into how COVID-19 and its treatment approaches may contribute to the development or exacerbation of acute AKI.

Compared to Zhao et al. our study analyzes a larger corpus of literature on COVID-2019 AKI, encompassing 2,806 papers versus their 1,507. This broader scope suggests that Zhao et al. may have overlooked pertinent studies, leading to an incomplete depiction of the reality. Our larger dataset enhances the robustness of our conclusions, offering a more comprehensive and accurate analysis of various bibliometric indicators, including publication and citation metrics, and the influence of contributing countries, institutions, authors, journals, keywords, and references. This underscores the necessity of a well-designed search strategy and the importance of incorporating expert feedback to refine search terms specific to the research area for improved precision. Our study provides targeted guidance and serves as a valuable resource for scholars in the field of COVID-2019 AKI. While the H-index is a useful tool for evaluating researcher impact, we acknowledge its potential to favor researchers from wealthier countries, thus contributing to disparities in research recognition. Therefore, we emphasize the importance of using additional metrics to provide a more balanced assessment. Additionally, by utilizing the H-index, we highlight the academic impact of researchers, further increasing the overall value of our study.

In summary, while recognizing the foundational work of Zhao et al. [1], our methodological advancements effectively address previous limitations and set the stage for more comprehensive and insightful bibliometric research. We recommend future researchers adopt and refine these advanced strategies to enhance the quality and impact of their studies across various scientific fields.

Funding Statement

The author(s) reported there is no funding associated with the work featured in this article.

Authors’ contributions

Heng Bai, Si-Yang Liu, Jie Tian and Yu Li organized and designed the manuscript. Heng Bai, Si-Yang Liu, Jie Tian and Yu Li organized and edited the retrieval formula. Heng Bai, Si-Yang Liu, Jie Tian and Yu Li created the Figure and Tables. All authors wrote the manuscripts and reviewed the finally version.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The datasets used during the present study are available from the corresponding authors upon reasonable request.