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Dialysis |




* Department of Medicine, Division of Nephrology, St. Michaels Hospital, Toronto, Ontario, Canada;
Department of Medicine, Division of Nephrology, Toronto General Hospital—University Health Network, Toronto, Ontario, Canada;
Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada;
Baxter Healthcare Corporation, Round Lake, Illinois
Correspondence: Drive Sharon J Nessim, 30 Bond Street, 8CC –Hemodialysis Unit, Toronto, Ontario, M5B 1W8 Canada. Phone: 416-864-6016; Fax: 416-864-5608; E-mail: nessims{at}smh.toronto.on.ca
| Abstract |
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Design, setting, participants and measurements: On the basis of data collected from 1996 to 2005 in the multicenter Baxter Peritonitis Organism Exit sites Tunnel infections database, the study population included 4247 incident Canadian PD patients: 1265 patients aged
70 yr and 2982 patients aged <70 yr. We defined two eras of PD initiation: 1996 to 2000 and 2001 to 2005.
Results: In a negative binomial model, older age was independently associated with a higher peritonitis rate (rate ratio [RR] 1.06 per decade increase; 95% CI 1.01 to 1.10; P = 0.008). However, this association was present only among those who initiated PD at an earlier time (RR 1.13 per decade increase; 95% CI 1.07 to 1.20; P < 0.001 in 1996 to 2000 versus 1.01 per decade increase; 95% CI 0.95 to 1.06; P = 0.81 in 2001 to 2005). Catheter-related infections were less frequent with increasing age regardless of era (RR 0.93 per decade increase; 95% CI 0.89 to 0.97).
Conclusions: The higher peritonitis rate observed in elderly patients may represent an era effect, as age was not associated with peritonitis among patients initiating PD between 2001 and 2005. In addition, catheter infection was less frequent with increasing age.
| Introduction |
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As life expectancy increases worldwide, more elderly patients are reaching end-stage renal disease (ESRD), requiring initiation of dialysis (7). Given that older dialysis patients have a higher comorbidity burden than do younger dialysis patients (7), older patients may not be similar to their younger counterparts in the propensity to develop PD-related infections, and the outcome of these infections may also differ. Although data on infectious complications in the general PD population are relatively robust, there are fewer data characterizing infectious complications of PD in the elderly patient.
In a study comparing PD-related infection rates among 63 nondiabetic patients older than 70 yr and 86 PD patients aged 40 to 60, there was a significantly higher peritonitis rate in the elderly, but no difference in exit site infection rate (8). In contrast, other studies have found similar peritonitis rates in older versus younger PD patients (9,10,11). Even among those with similar peritonitis rates, the spectrum of organisms has been reported to be different, with one study demonstrating increased Gram negative peritonitis (9), and another showing more Staphylococcus epidermidis peritonitis in the elderly (10). The latter study also found a lower exit site infection rate in the elderly.
The primary objective of the current study was to examine the impact of age on infection rates, infecting organisms, and outcomes of PD peritonitis and PD catheter infection. The secondary objective was to assess for an era effect with regard to the relationship between age and PD-related infections.
| Materials and Methods |
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For the purpose of providing demographic characteristics, patients were categorized as younger or older using a threshold of 70 yr (<70 yr versus
70 yr). Demographic data available for the current study include age, gender, race, cause of ESRD, diabetes status, modality before PD start (new to dialysis, transfer from HD, failed transplant, other/unknown) and PD modality (continuous ambulatory peritoneal dialysis [CAPD] versus automated peritoneal dialysis). For the latter variable, the first PD modality used, as well as the PD modality at the time of death, transfer to HD, transplantation or censoring were documented.
Given that the prospective cohort included patients who initiated PD over a 10-yr period, we defined two eras of patients to assess for an era effect: an earlier cohort consisting of those who initiated PD between 1996 and 2000, and a more recent cohort consisting of those who initiated PD between 2001 and 2005. The era cutoff was chosen based on a prehoc hypothesis that peritonitis rates would decrease around the time that mupirocin use was adopted as routine exit site care in Canada. This hypothesis was tested by determining the association between age and peritonitis rates for each year of PD initiation during the study.
Infectious Complications
The infectious complications studied were peritonitis and catheter infection. Catheter infection was defined as a PD catheter exit site infection and/or tunnel infection.
Infection Outcomes
Possible outcomes of infection in the database included death, catheter removal, resolution, cuff removal, other failure, and "no outcome listed." To ensure data validity, only data from centers with at least 95% of peritonitis outcomes reported were included in the outcome analyses.
Statistical Analyses
Continuous variables are reported as mean ± SD, and were compared between younger and older patients by means of the t test. Categorical variables are reported as percentages and were compared between groups using the
2 test. The association between age and the rate of peritonitis or catheter infection was tested in a univariate negative binomial regression model, as well as in a multivariable negative binomial model that included gender, race, diabetic status, cause of ESRD, modality before PD start, and PD modality as covariates. A negative binomial model was also used to study the relationship between organism-specific infection rates and age. The association between age and infection outcomes was tested with a logistic regression model. To assess for an era effect of age, we used an age x era interaction term as an initial screening; if found to be statistically significant, subsequent analyses were performed for each of the two eras. Statistical significance was defined as a P value of <0.05. All statistical analyses were performed using SAS (version 9.1).
| Results |
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70 yr of age and 2982 were <70 yr of age. The study sample included a total of 7319 yr of follow-up: 2041 yr of follow-up in those patients
70 yr and 5278 yr of follow-up in those patients <70 yr old. Demographic characteristics of patients in each age group are presented in Table 1. There were significant differences between younger and older PD patients: Elderly patients were more likely to be male (58% versus 54%; P = 0.015) and Caucasian (88% versus 80%; P < 0.001), and were less likely to be diabetic (35% versus 43%; P < 0.001) compared with younger patients. The distribution of the causes of ESRD was different between the age groups, with diabetes, glomerulonephritis, and cystic disease less likely to be the cause of ESRD in the older cohort compared with the younger cohort (P < 0.001). CAPD was the initial PD modality used in the majority of patients, with a higher proportion of older patients subsequently remaining on CAPD as compared with younger patients (56% versus 50%, P < 0.001).
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Infectious complications of PD were divided into peritonitis and catheter infection. The peritonitis data are presented in Table 2. A total of 3058 episodes of peritonitis occurred in 1605 patients. The remaining 2642 patients did not have any peritonitis episodes. In the univariate negative binomial regression model, increasing age was associated with a higher peritonitis rate (rate ratio 1.06 per decade; 95% CI 1.02 to 1.10; P = 0. 004). This effect persisted after adjustment for gender, race, diabetes, cause of ESRD, modality before PD start, and PD modality (rate ratio 1.06 per decade; 95% CI 1.01 to 1.10; P = 0.008).
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When peritonitis rates for individual organism categories were assessed overall, increasing age was associated with a higher Gram positive peritonitis rate (rate ratio 1.05 per decade increase; 95% CI 1.00 to 1.10, P = 0.043) and a higher coagulase negative Staphylococcus (CNS) peritonitis rate (rate ratio 1.07; 95% CI 1.01 to 1.14; P = 0.032). Although age did not affect Escherichia coli peritonitis in the overall analysis, an era effect was observed, with a higher E. coli peritonitis rate with increasing age from 1996 to 2000 (rate ratio 1.37 per decade increase; 95% CI 1.07 to 1.74; P = 0.011). but no association between E. coli peritonitis and age from 2001 to 2005 (rate ratio 0.94 per decade increase; 95% CI 0.74 to 1.18; P = 0.58). There was also a trend toward a lower S. aureus peritonitis rate with increasing age in the contemporary cohort (rate ratio 0.84; 95% CI 0.68 to 1.03; P = 0.096). The associations between age and the organisms causing peritonitis by era are described in Table 3.
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70 yr of age (4.9% versus 2.2%, P = 0.039). When age was assessed as a continuous variable, the odds ratio (OR) for peritonitis-related death was 1.37 per decade increase in age (95% CI 1.02 to 1.83; P = 0.035). There was no association between age and catheter removal after peritonitis (P = 0.31) nor between age and resolution of peritonitis (P = 0.11). There was a significant interaction between age and era for peritonitis-related death (P = 0.037). When outcome was assessed in each era, the higher frequency of peritonitis-related death with increasing age disappeared among those initiating PD between 2001 and 2005 (Table 4).
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| Discussion |
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The existing literature on the association between age and peritonitis rate is inconsistent (8,9,10,11,13). Several factors may be responsible for this variability. First, many of the studies that have looked at the effect of age on peritonitis have been small, single-center studies with limited statistical power. Second, different results may reflect the varying age cutoffs used to define "elderly" in the studies. Third, the era in which the patients received dialysis is quite variable, with some studies reporting on patients who were on PD in the late 1980s, and others reporting on more contemporary PD cohorts. The importance of the latter issue relates to the major advances in PD connectology (14–20) and exit site care (21–24) that occurred over this time period. Our study found that increasing age was associated with a higher peritonitis rate among patients initiating PD between 1996 and 2000, with the association disappearing among patients initiating PD in a more recent era. The lack of association between increasing age and peritonitis in recent years may reflect the fact that the "flush before fill" technique and the use of topical antibacterial agents provide an added "safety net" against contamination of the system in elderly patients who may have impaired vision or dexterity.
Surprisingly, increasing age was associated with a lower S. aureus catheter infection rate and a trend toward a lower S. aureus peritonitis rate in the more contemporary cohort. A lower incidence of S. aureus catheter infections among patients older than 60 has been previously reported (10). The basis for elderly patients having fewer S. aureus infections is unclear. Unfortunately, we do not have data on S. aureus nasal carriage, which has been linked to subsequent catheter infection and peritonitis (25–27). It is known that older patients are more compliant with some aspects of their PD (28), and it is plausible that they may also be more compliant with application of topical intranasal or exit-site ointments as prophylaxis against S. aureus infection.
In addition to the difference in S. aureus peritonitis, we found that increasing age was a risk factor for E. coli peritonitis among those initiating dialysis between 1996 and 2000. This is in keeping with a study by Kadambi et al. that reported a higher proportion of Gram negative peritonitis in older patients (9). It was thought that the higher incidence of constipation and diverticular disease in elderly patients may have predisposed these patients to Gram negative peritonitis by increasing translocation of organisms across the bowel wall. Although biologically plausible, the data to support the role of constipation and diverticulosis in development of peritonitis with enteric organisms are conflicting (29–33). Furthermore, the basis for the disappearance of the association between increasing age and E. coli peritonitis after the year 2000 is unclear. Because E. coli is not a common exit site organism, the change cannot be ascribed to introduction of exit site ointments.
The lower catheter infection rate among elderly patients has been reported previously (10). This may reflect more meticulous exit site care in this patient population, as it has been shown that patients under 55 yr of age are more likely to require retraining for breaks in exit site care protocols (34). Alternatively, it is plausible that the lower level of physical activity in this group may provide less opportunity for contamination.
On the basis of previous studies, the incidence of death due to peritonitis ranges from 2.2% to 5.9% (1,4,35–38). This is similar to the overall peritonitis-related mortality of 2.9% in our study. Interestingly, the higher risk of peritonitis-related death with increasing age disappeared in the more contemporary cohort, resulting in similar infection outcomes regardless of age among those who initiated PD after 2000. Although the basis for the improved peritonitis outcomes in elderly PD patients is unclear, one possibility is that the treatment of infection has become more standardized in recent years, and that this standardization of care may have preferentially benefited older patients, who were more susceptible to adverse outcomes with suboptimal infection management.
As with all large datasets, our study has several limitations. The data included in the database have not been validated against patient charts. The completeness of data entry varied across centers, and important variables such as markers of malnutrition and inflammation were not available. To limit errors associated with incomplete reporting of peritonitis outcome data from some centers, we limited the outcome analyses to a subset of patients from centers with complete data. Recognizing this as a limitation, we suggest these data are still of clinical importance, particularly because the number of patients and infection episodes included remain significantly higher than previous reports. Finally, we acknowledge limitations due to a lack of consensus for the definition of death attributable to peritonitis. We would, however, expect consistency in the reporting of death due to peritonitis among all ages within any given center, and as a result, believe this would not have affected our results.
In conclusion, our study demonstrates that although increasing age was associated with higher peritonitis rates among patients who initiated PD in the 1990s, age was not associated with peritonitis in a more contemporary PD cohort. Furthermore, catheter infection is less common with increasing age. Finally, no association between age and more frequent adverse outcomes of peritonitis was seen among those who initiated PD after the year 2000.
| Appendix 1 |
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1997 (n = 5): too few patients for analysis
1998 (n = 365): rate ratio 1.10 (95% CI 0.99 to 1.23, P = 0.084)
1999 (n = 539): rate ratio 1.17 (95% CI 1.06 to 1.29, P = 0.002)
2000 (n = 584): rate ratio 1.15 (95% CI 1.04 to 1.27, P = 0.006)
2001 (n = 685): rate ratio 0.97 (95% CI 0.89 to 1.06, P = 0.52)
2002 (n = 635): rate ratio 1.08 (95% CI 0.98 to 1.19, P = 0.13)
2003 (n = 646): rate ratio 1.02 (95% CI 0.90 to 1.17, P = 0.72)
2004 (n = 591): rate ratio 0.88 (95% CI 0.76 to 1.02, P = 0.84)
2005 (n = 196): rate ratio 1.03 (95% CI 0.91 to 1.17, P = 0.61)
| Disclosures |
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| Acknowledgments |
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| Footnotes |
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Received May 1, 2008. Accepted September 8, 2008.
| References |
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This article has been cited by other articles:
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S. J. Nessim, J. M. Bargman, and S. V. Jassal Relationship between double-cuff versus single-cuff peritoneal dialysis catheters and risk of peritonitis Nephrol. Dial. Transplant., January 26, 2010; (2010): gfq002v1 - gfq002. [Abstract] [Full Text] [PDF] |
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C. Castrale, D. Evans, C. Verger, E. Fabre, D. Aguilera, J.-P. Ryckelynck, and T. Lobbedez Peritoneal dialysis in elderly patients: report from the French Peritoneal Dialysis Registry (RDPLF) Nephrol. Dial. Transplant., January 1, 2010; 25(1): 255 - 262. [Abstract] [Full Text] [PDF] |
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S. J. Nessim, J. M. Bargman, P. C. Austin, R. Nisenbaum, and S. V. Jassal Predictors of Peritonitis in Patients on Peritoneal Dialysis: Results of a Large, Prospective Canadian Database Clin. J. Am. Soc. Nephrol., July 1, 2009; 4(7): 1195 - 1200. [Abstract] [Full Text] [PDF] |
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