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Volume: 17 Issue: 1 January 2019 - Supplement - 1

FULL TEXT

Over 5 Years of Excellent Graft Kidney Function Determinants: Baskent University Experience

Objectives: Kidney graft survival may be evaluated according to the duration of time with a functioning graft. Survival alone may not satisfy expectations of a successful kidney transplant if the graft kidney does not show excellent function. In our study, we analyzed the characteristics of kidney transplant recipients who showed excellent graft function after 5 to 10 years of follow-up in an aim to improve graft survival and to ensure the best kidney function in the long term.

Materials and Methods: We retrospectively evaluated graft function and demographic characteristics of 288 patients who underwent kidney transplant between January 2008 and December 2012.

Results: We found that 149 patients (51.7%) had excellent graft function, 88 patients (30.5%) had a functioning graft with a glomerular filtration rate lower than 60 mL/min and/or had signs of graft kidney dysfunction, and 45 patients (15.6%) experienced graft loss. Of 288 kidney transplant recipients enrolled in the study, most were male (56%), and mean age was 30.47 ± 14.36 years at time of transplant. Median time on dialysis was 39.09 ± 59.30 months. The overall graft survival rate in the patient group was 82.2% after 5 to 10 years of follow-up. Multivariate analysis showed that excellent graft survival predictors beyond 5 years were negative panel reactive antibody levels, lower donor age, shorter duration on dialysis, absence of acute rejection episodes, 3 or less HLA mismatches, lower immunosuppressive levels, and lower recipient age at transplant.

Conclusions: Lower panel reactive antibody levels, lower donor age, shorter duration on dialysis, absence of acute rejection episodes, 3 or less HLA mismatches, and lower recipient age at transplant are major determinants of excellent graft survival in our kidney transplant recipients.


Key words : Characteristics, Graft survival, Long term

Introduction

Successful kidney transplant promises better quality of life and results in longer survival in patients with end-stage renal disease.1,2 Over the past 20 years, short-term graft survival rates have improved; however, long-term graft survival still remains an important problem to be solved.3,4 Kidney graft survival may be evaluated according to the duration of time with a functioning graft, as graft survival alone may not satisfy expectations of a successful kidney transplant if the graft kidney does not show excellent function. Excellent graft function may be described as serum creatinine levels < 1.2 mg/dL, estimated glomerular filtration rate (eGFR) > 60 mL/min, and absence of coexisting proteinuria, glomerular hema­turia, and chronic allograft dysfunction. Preserving graft function and minimizing the modifiable risk factors are the main targets to improving graft outcomes.5,6 In our study, we analyzed the characteristics of kidney transplant recipients who showed excellent graft function after 5 to 10 years of follow-up with the aim of improving graft survival and ensuring the best kidney function in the long term.

Materials and Methods

Between January 2008 and December 2012, 288 patients underwent kidney transplant. We retro­spectively evaluated graft function and demographic characteristics of this patient group. The standard immunosuppressive treatment in our center con­sisted of a calcineurin inhibitor or a mammalian target of rapamycin inhibitor, prednisolone, and mycophenolate mofetil.

Continuous variables are expressed as means and standard deviation. To evaluate the differences between mean values, we used t tests. Chi-square tests were used for categorical variables, and P ≤ .05 was accepted as significant. Statistics were mainly calculated with the use of SPSS version 20.0 software (Statistical Package for the Social Sciences, Inc., Chicago, IL, USA).

Results

During a 5- to 10-year follow-up of 288 patients who received kidney transplants between January 2008 and December 2012, 149 patients (51.7%) showed excellent graft function, 88 patients (30.5%) had a functioning graft with eGFR lower than 60 mL/min and/or had coexisting signs of graft kidney dysfunction, and 45 patients (15.6%) experienced graft loss. Determinations of patient status were made by analyses of recipient and donor characteristics, mean serum immunosuppressive drug levels, acute rejection episodes, and biochemical parameters.

Most patients in our study group were male (56%), and the mean age was 30.47 ± 14.36 years at the time of transplant. Median time on dialysis was 39.09 ± 59.30 months.

The overall graft survival rate was 82.2% in our kidney transplant recipients after 5 to 10 years of follow-up. The 149 recipients (51.7%) with excellent graft function had eGFR > 60 mL/min without coexisting proteinuria or glomerular hematuria or any signs of chronic allograft dysfunction after at least 5 years. The 88 patients (30.5%) with a functioning graft had eGFR lower than 60 mL/min or proteinuria higher than 300 mg per 24 hours without need for hemodialysis. Six patients (2%) died due to cardiovascular and infectious reasons.

We found that donor age, recipient age, low serum creatinine levels in the 1st month and 12th month after transplant, negative panel reactive antibody (PRA), 3 or less HLA mismatches, and lower mean immunosuppressive levels were the major determinants of excellent graft function after 5 to 10 years of follow-up.

The 149 patients with excellent graft function had lower donor age (39.53 ± 11.28 vs 47.36 ± 18.21 y; P = .01), lower recipient age (30.47 ± 14.36 vs 38.45 ± 19.16 y; P = .01), shorter duration on dialysis (37.09 ± 59.30 vs 53.15 ± 71.24 mo; P = .01), 0% of PRA class I and II levels (85.9% vs 71.2%; P = .01), 3 or less HLA mismatches (77.8% vs 61.6%; P = .001), and lower incidence of acute rejection episodes (5.4% vs 23.6%; P = .001) than patients who had lower eGFR, higher proteinuria, or both. Comparisons are summarized in Table 1.

Multivariate analysis showed that excellent graft survival predictors beyond 5 years were negative PRA levels, lower donor age, shorter duration on dialysis, absence of acute rejection episodes, 3 or less HLA mismatches, lower immunosuppressive levels, and lower recipient age at transplant.

Discussion

We aimed to determine the characteristics of the kidney transplant recipients who had excellent graft function after 5 to 10 years of transplant. These findings could improve our kidney transplant recipient selection criteria and result in better monitoring of high-risk recipients in our population. Our population showed an overall graft survival rate of 82.2%, with 51.7% showing excellent graft survival after 5 to 10 years of follow-up.

Most of our population (82.9%) received kidneys from living donors. Studies have indicated that a 12-month optimal graft function without any acute rejection episodes is a strong indicator of long-term graft survival.7-9 In our long-term follow-up study, we showed that negative PRA levels before transplant, absence of proteinuria in the first year after transplant, and 3 or less HLA mismatches were also determinants of excellent graft function. We also found that patients who were categorized as having excellent graft function over 5 years had lower acute rejection episode rates than patients with signs of graft kidney dysfunction or graft loss.

Patients at our center receive an immunosup­pressive regimen composed of a calcineurin inhibitor in the first year after kidney transplant. We have not experienced major adverse effects that may prevent our recipients against acute rejection episodes compared with a mammalian target of rapamycin-based regimen. As previously reported, lower plasma creatinine levels and lower proteinuria levels at 12 months after transplant are strong determinants of excellent graft function after 5 years.5,9 Our results are comparable with the literature, as we also found that lower creatinine levels with concomitant lower proteinuria at 12 months posttransplant were predictors of excellent graft function.

Other reported determinants of graft survival are lower recipient age at transplant, donor age, duration of dialysis before transplant, and lower PRA levels.10,11 Although younger kidney transplant recipients are considered to have an active immune response compared with older recipients, they also have smaller atherosclerotic vessels that may affect graft survival. Relatively lower blood transfusion rates after recombinant erythropoietin administration in our hemodialysis population may be the major determinant of higher rates of PRA-negative kidney transplant recipients in our center.12,13

Our study had several limitations, including its retrospective design, different immunosuppressive regimens, and different donor characteristics. Living-donor kidney transplant is still the leading option in our country and in our center, which is a contributing factor of better graft outcomes. Nevertheless, our study included a large number of kidney transplant recipients and had a long follow-up of 5 to 10 years. In our patient group, 51.7% had excellent graft function. Although this is an excellent rate for long-term graft survival, we believe that better results can be achieved by using our findings for better patient monitoring.

Conclusions

Lower PRA levels, lower donor age, shorter duration on dialysis, absence of acute rejection episodes, 3 or less HLA mismatches, and lower recipient age at transplant are major determinants of excellent graft survival in our kidney transplant recipients. The results may be helpful to determine future selection criteria for kidney transplant recipients and donors in our center.


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Volume : 17
Issue : 1
Pages : 75 - 77
DOI : 10.6002/ect.MESOT2018.O12


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From the 1Department of Nephrology, the 2Department of Public Health, the 3Department of General Surgery and Transplantation, Baskent University Ankara Hospital, Ankara, Turkey
Acknowledgements: The authors have no sources of funding for this study and have no conflicts of interest to declare
Corresponding author: Burak Sayin, Baskent University Ankara Hospital, Nephrology Department, Fevzi Cakmak Caddesi, 5. Sokak No:48, 06480, Bahcelievler, Cankaya, Ankara, Turkey
Phone: +90 312 212 2912 ext. 5226
E-mail: buraksayin@hotmail.com