1,720,973 research outputs found
A joint transition model for evaluating eGFR as biomarker for rejection after kidney transplantation
No full textThe estimated glomerular filtration rate (eGFR) quantifies kidney graft function and is measured repeatedly after transplantation. Kidney graft rejection is diagnosed by performing biopsies on a regular basis (protocol biopsies at time of stable eGFR) or by performing biopsies due to clinical cause (indication biopsies at time of declining eGFR). The diagnostic value of the eGFR evolution as biomarker for rejection is not well established. To this end, we built a joint model which combines characteristics of transition models and shared parameter models to carry over information from one biopsy to the next, taking into account the longitudinal information of eGFR collected in between. From our model, applied to data of University Hospitals Leuven (870 transplantations, 2 635 biopsies), we conclude that a negative deviation from the mean eGFR slope increases the probability of rejection in indication biopsies, but that, on top of the biopsy history, there is little benefit in using the eGFR profile for diagnosing rejection. Methodologically, our model fills a gap in the biomarker literature by relating a frequently (repeatedly) measured continuous outcome with a less frequently (repeatedly) measured binary indicator. The developed joint transition model is flexible and applicable to multiple other research settings
Bias by censoring for competing events in survival analysis
No full textsponsorship: There was no specific funding provided for the study. MC had financial support from the Fonds Wetenschappelijk Onderzoek (Research Foundation-Flanders) and the Agency for Innovation and Entrepreneurship by an "Applied Biomedical Research with a Primary Social Finality" project grant IWT.150199; MN is senior clinical investigator of the Fonds Wetenschappelijk Onderzoek (Research Foundation-Flanders) (grant 1844019N). The funding agencies had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication. All authors had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis (Fonds Wetenschappelijk Onderzoek (Research Foundation-Flanders), Applied Biomedical Research with a Primary Social Finality, Fonds Wetenschappelijk Onderzoek (Research Foundation-Flanders)|IWT.150199, 1844019N)status: Publishe
Primary FSGS is not associated with worse kidney outcome compared with other FSGS subtypes
No full textBackground Studies that compare kidney outcomes across patients with different forms of focal segmental glomerulosclerosis (FSGS) are lacking. Methods This retrospective study compared annual estimated glomerular filtration rate (eGFR) slope and kidney failure rate (eGFR <15 mL/min/1.73 m(2) or initiation of kidney replacement therapy) across patients with biopsy-proven primary, maladaptive, genetic and undetermined FSGS. Patients were included from two Belgian tertiary referral hospitals, from 2010 until 2022. Associations between covariates and kidney failure were estimated using Cox and Fine and Gray models. eGFR slopes were estimated using linear mixed-effects models. Results Eighty-two patients were subdivided into primary (28.1%), maladaptive (40.2%), genetic (14.6%) and undetermined FSGS (17.1%) groups. Kidney failure occurred in 22 patients (26.8%). Primary FSGS patients exhibited higher baseline eGFR and less chronic changes on biopsy. The annual eGFR slope was -2.5 mL/min in primary, -2.5 mL/min in maladaptive, -4.6 mL/min in genetic and -4.4 mL/min in undetermined FSGS. Female sex was associated with a lower kidney failure rate and higher eGFR slope. Higher proteinuria at biopsy was associated with a higher kidney failure rate, lower eGFR slope and a higher mortality rate. Global sclerosis on kidney biopsy was associated with lower baseline eGFR, while a higher percentage of segmental sclerosis rather associated with more rapid eGFR decline [-1.5 mL/min/year per 10% increase, 95% confidence interval (-2.2, -0.7)]. Conclusions Patients with primary FSGS were biopsied earlier in their disease course and exhibited surprisingly good kidney outcome. Overall, sex, baseline eGFR, proteinuria and the degree of focal and global glomerulosclerosis play a more important role in estimating the prognosis of patients with FSGS than merely the FSGS etiology.FUNDING
D.D. is supported by a PhD Fellowship grant fundamental research from the Research Foundation Flanders (F.W.O.) (grant number 11L5622N). M.C. is supported by the Research Foundation Flanders (F.W.O.) (grant 12D6423N). A.H.V.C. is supported by a postdoctoral grant from the University Hospitals Leuven (KOOR) and a Research Foundation Flanders (FWO) SBO project (S006722N). B.K.M. is a senior clinical investigator of F.W.O. (1 800 820 N) and received grant support from KU Leuven (3M190551 and C14/21/103).
ACKNOWLEDGEMENTS
This study was approved by the ethical committees of the academic hospitals of UZ Leuven and UZ Ghent (study reference S66295). All study participants were informed on the use of their data for this retrospective analysis
Toegepaste biostatistische benaderingen voor afstoting en uitkomsten na niertransplantatie. Met focus op overlevings-, longitudinale en gecombineerde analyse.
No full textstatus: Publishe
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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