Araştırma Çıktıları

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    Dynamic predictions of kidney graft survival in the presence of longitudinal outliers
    (SAGE PUBLICATIONS LTD, 2021-01-01) Asar, Ozgur; Fournier, Marie-Cecile; Dantan, Etienne
    In kidney transplantation, dynamic predictions of graft survival may be obtained from joint modelling of longitudinal and survival data for which a common assumption is that random-effects and error terms in the longitudinal sub-model are Gaussian. However, this assumption may be too restrictive, e.g. in the presence of outliers, and more flexible distributions would be required. In this study, we relax the Gaussian assumption by defining a robust joint modelling framework witht-distributed random-effects and error terms to obtain dynamic predictions of graft survival for kidney transplant patients. We take a Bayesian paradigm for inference and dynamic predictions and sample from the joint posterior densities. While previous research reported improved performances of robust joint models compared to the Gaussian version in terms of parameter estimation, dynamic prediction accuracy obtained from such approach has not been yet evaluated. Our results based on a training sample from the French DIVAT kidney transplantation cohort illustrate that estimates for the slope parameters in the longitudinal and survival sub-models are sensitive to the distributional assumptions. From both an internal validation sample from the DIVAT cohort and an external validation sample from the Lille (France) and Leuven (Belgium) transplantation centers, calibration and discrimination performances appeared to be better under the robust joint models compared to the Gaussian version, illustrating the need to accommodate outliers in the dynamic prediction context. Simulation results support the findings of the validation studies.
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    Graft and Patient Survival in Kidney Transplant Recipients Over the Age of Sixty-Five
    (CUREUS INC, 2022-01-01) Yilmaz, Gulay; Ozdemir, Ebru; Yildar, Murat; Karayagiz, Hamit; Berber, Ibrahim; Cakir, Ulkem
    Introduction: Elderly patients have increased morbidity and mortality compared to younger patients due to existing comorbid diseases and chronic immunosuppression. Therefore, the option of kidney transplantation for renal replacement therapy in elderly patients is still being controversial. Our aim in this study was to evaluate graft function, graft and patient survival, and associated factors in kidney transplant recipients over 65 years of age, at 11 years of follow-up. Methods: The study included 53 patients aged 65-76 years, out of a total of 1319 patients who underwent live kidney transplantation in the Organ Transplant Center of Acibadem International Hospital between October 2010 and July 2021. Demographic characteristics and creatinine values were recorded. Graft survival rates and patient survival rates at one, three, and five years were analyzed. Results: Fifty-three patients, 14 female, 39 male, aged 65-76 years were included in the study. The follow-up period of the patients was 7-125 months. During the follow-up, 20 patients died. Graft loss occurred in two of 20 patients who died, and 18 patients died with working grafts. Graft loss developed in two of the 33 surviving patients. In the whole group, one-, three-, and five-year patient survival rates were 94\%, 81\%, and 76\%, respectively. Conclusion: These results emphasize that kidney transplantation is a viable treatment option in elderly patients who have been well evaluated before kidney transplantation.
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    Novel Once-daily Extended-release Tacrolimus Versus Twice-daily Tacrolimus in De Novo Kidney Transplant Recipients During the Early Posttransplant Period
    (GALENOS PUBL HOUSE, 2022-01-01) Yilmaz, Gulay; Ozdemir, Ebru; Yildar, Murat; Karayagiz, Abdulhak Hamit; Berber, Ibrahim; Cakir, Ulkem
    Objective: Tacrolimus is used in more than 80\% of kidney transplant recipients due to its ability to avoid rejection. Irregularities in tacrolimus level may affect clinical outcomes by subjecting patients to adverse events associated with graft rejection or immunosuppressive therapy. There are two forms of tacrolimus