| Abstract|| |
One of the advantages of peritoneal dialysis (PD) compared to hemodialysis is it can be performed at home. The present study aims at determining the long-term survival of patients and technique survival and investigates the risk factors affecting the mortality rate in PD patients. The study was conducted on 290 patients undergoing PD in the main PD center in Shiraz, Iran, between April 2002 and March 2012. The patients' survival rate and the factors affecting their survival were assessed using the Kaplan-Meier method. Besides, log-rank method was used to compare survival among different levels of the categorized variables. Cox regression model was used for introducing the risk factors affecting the patients' survival. The mean of the patients' survival at the end of the follow-up period was 15.42 ± 13.97 months. The patients' 1-, 2-, 3-, and 5-year survival rates were 85%, 72%, 57%, and 22%, respectively, and the median survival time was 11.64 months. Forty-three patients (14.8%) changed their treatment method to hemodialysis. The patients' 1-, 2-, 3-, and 5-year technique survival rates were 90%, 81%, 72%, and 47%, respectively. Age and hemoglobin level were the most significant factors in the patients' survival. Hemoglobin level was the most important factor in technique survival.
|How to cite this article:|
Rajaeefard A, Sarvandian S, Rezaianzadeh A, Roozbeh J. Analyzing the long-term survival of the patients undergoing peritoneal dialysis in the peritoneal dialysis center in Shiraz, 2002-2011. Saudi J Kidney Dis Transpl 2016;27:1211-6
|How to cite this URL:|
Rajaeefard A, Sarvandian S, Rezaianzadeh A, Roozbeh J. Analyzing the long-term survival of the patients undergoing peritoneal dialysis in the peritoneal dialysis center in Shiraz, 2002-2011. Saudi J Kidney Dis Transpl [serial online] 2016 [cited 2020 Jan 26];27:1211-6. Available from: http://www.sjkdt.org/text.asp?2016/27/6/1211/194626
| Introduction|| |
Chronic kidney disease (CKD)  is considered one of the world's general health challenges and are linked to an increase in mortality and morbidity, impose high economic burden on the health-care system, and affect the patients as well as their families. ,,
Renal transplantation is the best treatment for the patients suffering from ESRD. However, due to the increasing incidence and prevalence of kidney diseases and decrease in the number of donors, a large number of such patients undergo treatment with dialysis. , Peritoneal dialysis (PD) has been widely used worldwide since 1980 ,, and in Iran since 1997. Today, forty PD centers with more than 1000 patients are active in Iran. In 2006, nearly 3% and in early 2008, 6.7% of ESRD patients were under treatment by PD. This rate has been increasing during the past few years. ,, Among all the dialysis patients in Iran, 93.5% and 6.5% are being treated by hemodialysis (HD) and PD, respectively. One of the advantages of PD compared to HD is the possibility of treatment at home. However, there are still debates on whether there is a higher survival in patients on PD compared to those on HD.  Most studies have shown that PD is, at least, as effective as HD. Furthermore, some studies conducted in Canada showed that in comparison to HD, PD has a higher survival in the first years of treatment. ,,
Higher survival rates of the patients undergoing PD in the first two years of treatment compared to those undergoing HD have been reported by some studies. ,, Other reasons for using PD as the treatment of choice include reduction of treatment expenses, ease, and the possibility of treatment at home. Moreover, infection and its resulting problems have been shown to increase in the patients undergoing HD in the past 10 years. , Thus, the present study aims to determine the long-term survival of patients and technique survival and investigates the risk factors affecting the mortality rate of the patients undergoing PD.
| Methods|| |
The present retrospective cohort study was conducted on 318 consecutive PD patients in Imam Reza Clinic Peritoneal Dialysis center (the main PD center in Shiraz supervised by Shiraz University of Medical Sciences, Shiraz, Iran) from April 2002 to March 2012. The inclusion criteria of the study were patients being over 18 years old and having been under treatment for at least 30 days. The information regarding the survival time, demographic characteristics, laboratory findings, body mass index (BMI), the underlying causes of CKD, and comorbidities were collected from the patients' records in the center.
In this study, Kaplan-Meier method was utilized to compute the patients' survival rate and determine the effects of age, sex, marital status, blood group, BMI, laboratory findings, type of the underlying disease, and comorbidities on their survival. In addition, survival was compared among different levels of categorized variables using the log rank method. Besides, Cox regression model was used to investigate the effective risk factors in the patients' survival, and the proportionality assumption in the Cox model was evaluated through graphical methods. Survival time was considered from the beginning of the treatment up to death. The patients who changed their treatment method, underwent renal transplantation, or were lost during the study for any reason were considered as censored cases. Moreover, changing the treatment to HD was considered as the end point for computing the technique survival. All the statistical analyses were performed using the SPSS statistical software (v. 19) and STATA (v. 11).
| Results|| |
In the dialysis center under study, a total of 318 patients underwent PD between 2002 and 2011. After excluding the patients who did not fulfill the inclusion criteria of the study, 290 patients were included in the study. Descriptive clinical and laboratory findings of the 290 patients are shown in [Table 1] and [Table 2]. The male:female ratio was 1:1.14. The mean age was 47.62 ± 16.35 years with the highest frequency observed in the 40-59-year-old age group (120 patients, 41.4%). BMI of 161 patients was within the acceptable range. During the follow-up period, 68 patients (23.4%) died, 91 patients (31.4%) underwent transplantation, 43 patients (14.8%) changed their treatment method to HD (the reasons for this are shown in [Table 3], and 88 patients (30.3%) are still receiving PD.
|Table 1: Frequency distribution of the clinical and demographic variables in the patients undergoing PD.|
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|Table 2: Mean laboratory parameters of the patients undergoing peritoneal dialysis at the beginning of the treatment.|
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|Table 3: Reasons for change of treatment to hemodialysis in the patients undergoing peritoneal dialysis.|
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The mean of the patients' survival was 15.42 ± 13.97 months. The patients' 1-, 2-, 3-, and 5year survival rates were 85%, 72%, 57%, and 22%, respectively, and the median of survival time was 11.64 months [Figure 1].
|Figure 1: Survival curve of peritoneal dialysis patients using the Kaplan–Meier method.|
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Univariate analysis showed that being diabetic, serum level of hemoglobin, creatinine, and age at the beginning of treatment to be the significant factors in survival (0.021, 0.024, 0.02, and 0.0002, respectively). [Figure 2] shows the significant difference between survival curve of patients with more and less than Hb levels of 12 g/dL using the Kaplan-Meier method.
|Figure 2: Kaplan–Meier estimate of cumulative survival in patients with hemoglobin level more and <12 mg/dL (P = 0.024).|
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Univariate hazard ratios (HRs) for the mentioned variables using Cox regression are presented in [Table 4].
|Table 4: Hazard ratio of death in univariate analysis based on the study variables.|
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The variables with P <0.05 in the univariate analysis were entered into the Cox model and Forward Stepwise (likelihood ratio) method was utilized in this model. As [Table 5] depicts, in the final model, age and hemoglobin were shown as the effective factors in the survival of the patients undergoing PD. For each one year increase in age, 1.05-fold increase could be observed in the risk of death. In addition, the HR of the patients with <12 hemoglobin was 2.73-fold more than that of those with hemoglobin >12 g/dL.
|Table 5: Modeling the effective factors in survival of the patients undergoing peritoneal dialysis using Cox regression model.|
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Among the patients under study, 43 (14.8%) changed their treatment method to hemodialysis. Moreover, 1-, 2-, 3-, and 5-year technique survival of the patients was 90%, 81%, 72%, and 47%, respectively [Figure 3].
|Figure 3: Technique survival curve of the patients undergoing peritoneal dialysis using the Kaplan–Meier method.|
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Peritonitis was the most important cause of treatment change to HD in this study (26 patients, 56%). In univariate as well as multivariate analyses, serum hemoglobin level was among the significant factors affecting technique survival [Table 6].
|Table 6: Modeling the effective factors in the technique survival of the patients undergoing peritoneal dialysis using Cox regression model.|
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| Discussion|| |
In this study, the mean age of the patients was lower than other studies. In two studies performed by Hakemi et al and Akhlaghi et al in Tehran, the patients' mean age was 50 years. , However, in the study by Sipahioglu et al conducted in Turkey in 2008, the mean age of the patients was 46 ± 14.3 years which is similar to the results of the present study. 
Our patient survival rate was lower than other reports. ,,,, Han et al reported that the 5year patient and technique survivals were 69.8% and 71.9%, respectively, on Korean patients on continuous ambulatory PD therapy.  In 2006, the United States Renal Data System reported a 5-year patient survival of 32%.  Disparity in patient survival in different studies might be due to the difference in demographic characteristics of patients (age, comorbid diseases, race, and genetic factors).
On the other hand, the technique survival in this study of 90%, 81%, 72%, and 47%, at 1-, 2-, 3-, and 5-year, respectively, is higher than in other studies conducted in Iran. Hakemi et al reported a 1-, 2-, 3-, 4-, and 5-year technique survival of 88%, 72%, 56%, 39%, and 32%, respectively. However, in a study by Utas et al in Turkey reported the 5-year technique survival to be 77.4%.  In all the previous studies, as in ours, peritonitis was the most common reason for treatment change to hemodialysis. ,
We showed that diabetes and hypertension are the main causes of renal failure in dialysis our patients, which is in agreement with manyother studies. ,,,,
Studies investigated the relationship of BMI to mortality and morbidity in patients on PD with conflicting results. A study conducted in Australia and New Zealand demonstrated a significant association between obesity and lower patient survival (P <0.001).  In our study, no effect of BMI on PD outcome was observed. This is in agreement with the study by Aslam et al. 
Although low-serum albumin level has been shown to be associated with increase in mortality, this was not the case in our patients. ,,
Multivariate analysis has shown that the age of the patients at the baseline was one of the significant factors in survival, which is consistent with the results of other studies. ,
In addition, multivariate analysis revealed that hemoglobin rate (<12 and >12 g/dL) as being also one of the significant factors in survival (P = 0.004). Avram et al also showed hemoglobin rate to be significant at the beginning show that hemoglobin level before treatment initiation was effective in survival (P = 0.032). 
In conclusion, we confirmed that age and Hb level are the two most important factors affecting the PD patients' mortality rate.
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Department of Epidemiology, School of Health and Nutrition, Shiraz University of Medical Sciences, Shiraz
[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]