Impact of type of donor on graft and patient survival rate in kidney transplanted patients in Iran

1School of Medicine, Urmia University of Medical Sciences, Urmia, Iran 2Public Health Department, Tabriz Branch, Islamic Azad University, Tabriz, Iran 3Nephrology, and Kidney Transplant Research Center, Department of Urology, Imam Medical Center, Urmia University of Medical Sciences, Urmia, Iran 4Department of Epidemiology and Biostatistics, School of Public Health, Urmia University of Medical Sciences, Urmia, Iran 5Nephrology, and Kidney Transplant Research Center, Department of Urology, Imam Medical Center, Urmia University of Medical Sciences, Urmia, Iran


Introduction
End-stage renal disease (ESRD) is an increasing problem in the world (1).Kidney transplant is considered as a preferred therapeutic method for patients with ESRD and it is offered importantly for better quality of life, cardiovascular stability and improved survival (2)(3)(4).Options of organ transplant include living related donor (LRD), living unrelated donor (LURD) and cadaveric donor while the cadaveric is an important option, but graft survival rate from an alive donor is more than the cadaver (5).Therefore, regarding survival rate of one-year in the 1960s from alive donor, kidney transplant survival was 75% to 90% and in cadaver was 50% to 60%.While during 1970 to 1980s, one-year survival rate had increased rapidly in cadaveric kidney transplant.Nowadays, oneyear survival rate of cadaveric kidney transplant is 89% and from alive donors is 95%.During this period the longterm survival rate also improved and now the average lifespan of a transplant from alive donors and cadaveric kidney transplant is around 20 years and close to 14 years, respectively (6).High survival with alive donor compared to cadaver donor has been widely reported (7).Therefore, a shift towards alive donor transplants is increasing worldwide (8).A similar trend has been observed in our unit over the last decade (9).

Objectives
The purpose of this study was to evaluate the effect of type of donor on graft and survival rate of patients in the Imam Khomeini hospital in transplantation center of Urmia city, Iran.

Study population
This study was a cross-sectional study and the sample of study consisted of all patients who had received kidney transplant from the beginning of 2001 until the end of 2011.The data of patients were collected using a checklist through available records in the kidney transplantation center and the clinic of sector in Imam Khomeini hospital.To determine the status of the patients or graft survival, phone number of patients were used to follow-up and complete the data.To comply with ethical aspects, all stages of collecting, maintaining appropriate data and the results of data were reported anonymously.Transplantation recipients were identified regarding urinary tract infection after transplantation and studied variables in this study were included the age and gender of the kidney donor and recipient, type of dialysis, causes of death, immunosuppression, cold ischemia, warm ischemia and time on dialysis before transplant.In this study, transplantation date is considered as the first event (initial event) and date of death or last follow-up is considered as the final event (end-point event).

Ethical issues
1) The research followed the tenets of the declaration of Helsinki.2) Informed consent was obtained 3).This study was approved by the Ethics Committee of Urmia University of Medical Sciences.

Statistical analysis
To calculate the graft survival rate, the transplant date was considered as the first event (initial event) and kidney transplant failure date that led to dialysis and in some cases led to death was considered as the event end (endpoint event).Kaplan-Meier method was used to calculate the patient survival rate and as well as log-rank test was used to compare the survival curves.Cox regression model was applied for modeling the factors affecting survival rate.Mann-Whitney U test was used to compare the continuous variables and x 2 test was used to compare classified data.Also all relations were presented by odds ratios (ORs) and 95% confidence intervals (CIs).The data were analyzed using SPSS version 19.The level of significance considered less than 0.05.

Discussion
Kidney transplant among alive donors is becoming popular because of better organs and excellent outcomes (9).In this study, the results showed that LRD is one of the factors affecting graft survival, so that graft survival rate showed high length among patients who their graft was from LRD compared to LURD and cadaveric, which the results are consistent with study by Bakr and Ghoneim (10), and others (11)(12)(13)(14).However, several studies did not find a significant relationship between type of donor and graft survival rate (5,(15)(16)(17)(18).In our study, risk of graft rejection in LRD and cadaver recipients was less than that of reference group and were 0.252 and 0.945, respectively (hazard ratio and regression coefficient; Table 2).Despite no significant relationship was detected between the type   of donor and patient survival rates (Table 3), survival rate was high among LRD recipients compared to LURD and cadaver recipients.However, in a study by Fuggle et al, a significant relationship was detected between type of donor and survival rate of patients (19).In this study, one possible reason for the lower survival rate of graft and patients among LURD recipients and cadaver recipients compared to LRD recipients may be related to high occurrence of acute rejection in patients who have received organ from LURD and cadaver organ.Likewise, survival rate in LRD recipients for 1 and 5 years were 100% and 100%.We also found, graft survival rates were 96% and 96% for 1 and 5 years, respectively.In the study of Patel et al, the survival rates of patients in LRD recipients for 1 and 5 years were 93.8% and 83.1%, and graft survival rates were 96.1% and 89% for 1 and 5 years, respectively (20).Additionally patient survival rates in LURD recipients for 1 and 3 years were 94% and 90%, while graft survival rates 94% and 87% for 1 and 3 years, respectively.In the study by Ahmed et al, the survival rates of patients in LURD recipients for 1 and 3 years were 97.7% and 95%, while graft survival rates were 98.7% and 93.7% for 1 and 5 years, respectively (9).Log-rank test showed a statistical significant difference between graft survival rate (P = 0.038) and patients' survival rate (P = 0.043), for the recipients regarding the type of donor, while in the study of Markus et al, no significant difference was reported between graft survival rate (P = 0.91) and patients' survival rate (P = 0.686) (21).Numerous studies have reported the chronic glomerulonephritis as main cause of ESRD in patients (9,21).There was no significant difference between recipients regarding the type of donor.Similar to the results of numerous studies, differences were observed between recipients' age (P = 0.34) and donors' age (P = 0.001) (1,21,22).In the study of Tekin et al, no significant difference was observed in recipients' age (P = 0.582) (4).Additionally, differences were observed in recipients' gender (P = 0.018), donors' gender (P = 0.001), time of dialysis (P = 0.002), warm ischemia time (P = 0.001), serum creatinine at discharge (P = 0.01) and also on other variables like type of immunosuppression (P = 0.48) and cold ischemia time (P = 0.07).

Conclusion
The results of this study showed that LRD is one of the factors affecting graft survival.Hence, graft survival rate showed high length among patients who their graft was from LRD compared to LURD and cadaveric.

Limitations of the study
It was a single-center non-randomized study.All patients did not respond to our call.

Figure 1 .
Figure 1.Comparison patient survival rate according to type of donor after transplantation in transplanted patients.

Figure 2 .
Figure 2. Comparison graft survival rate according to type of donor after transplantation in transplanted patients.

Table 1 .
Characteristics of the patients according to type of donor RT, renal transplantation; HD, hemodialysis; PD, peritoneal dialysis; LDR, living related donor; ULRD, unrelated living donor; BMI, body mass index.