Perit Dial Int
29(3):
292-296
2009
© 2009 International Society for Peritoneal Dialysis
TECHNIQUE FAILURE AND CENTER SIZE IN A LARGE COHORT OF PERITONEAL DIALYSIS PATIENTS IN A DEFINED GEOGRAPHIC AREA
Bayode Afolalu1,2,3,
Laura Troidle1,2,3,
Osasu Osayimwen1,
Jaya Bhargava4,
Jenny Kitsen4 and
Fredric O. Finkelstein1,2,3,5
Hospital of St. Raphael,1 New Haven
CAPD,2 Renal Research
Institute,3 Network of New England (Network
#1),4 and Yale University,5
New Haven, Connecticut, USA
Correspondence to: F.O. Finkelstein, Department of Nephrology, Hospital of St.
Raphael, 1450 Chapel Street, New Haven, Connecticut 06511 USA.
fof{at}comcast.net
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ABSTRACT
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Background: Hemodialysis (HD) and peritoneal dialysis
(PD) are both viable options for renal replacement therapy. Technique failure
has been shown to be a major problem in PD therapy.
Objective: To examine the relationship between center
size and PD technique failure.
Setting: ESRD Network #1 (NW1).
Design: Retrospective review of NW1 database.
Patients and Methods: 5003 incident PD patients between
2001 and 2005 in 105 PD units were included. Patients were grouped into 2
based on center size: group A, patients in units with 
25 patients, and
group B, patients in units with >25 patients. Outcome measures were
analyzed for the first and second years of PD therapy. Patients were censored
at transplantation, transfer to HD, or death.
Outcome Measures: Technique failure and mortality
reported as death in Standard Information Management Systems (SIMS) database
(NW1 data system).
Results: Technique failure rates were significantly
higher in group A for year 1 (odds ratio: 1.36, p = 0.005) and for
year 2 (odds ratio: 1.35, p = 0.03). Mortality rates were not
statistically different between the 2 groups.
Conclusion: Technique failure was higher in units with
25 patients than in units with >25 patients. There was no difference in
mortality between the 2 groups. The majority of patients in NW1 receive care
in small units.
KEY WORDS: Center size; technique failure.
Technique failure rate is defined as the proportion of dialysis patients
switching from one modality to another. Even though mortality rates in
patients on hemodialysis (HD) and peritoneal dialysis (PD) have been shown to
be comparable
(1–3),
technique failure occurs more frequently in PD
(1,4–7)
and remains a major problem with this dialysis modality. The major causes of
technique failure are peritonitis, ultrafiltration failure, and psychosocial
issues (1). However, other
factors may contribute to technique failure. One factor that has been
suggested is center size. There are limited studies on the effect of center
size on technique failure and mortality. Previous studies comparing center
size and technique failure or mortality were based on reviews of the
Netherlands dialysis database (RENINE), a Canadian database, and a Baxter
Healthcare database
(8–10).
These studies suggest that increased experience with PD may result in improved
outcomes, with reduced technique failure rates in larger centers. However,
there are conflicting results when comparing mortality rates. The present
study was done to evaluate the effect of center size on technique failure or
mortality in a defined geographic area in the United States (ESRD Network #1).
Of the 18 networks in the United States, Network #1, which includes the New
England states, has the highest PD utilization rate: 11% of prevalent
end-stage renal disease (ESRD) patients in this area are maintained on PD
compared to 8% in the general USA ESRD patient population based on the 2005
Summary Report of the ESRD Networks' Annual Reports submitted to Centers for
Medicare and Medicaid Services (CMS)
(11).
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PATIENTS AND METHODS
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This study was designed to determine if there is a difference in technique
failure and mortality between units caring for 25 patients or fewer versus
those caring for more than 25 patients. This study is based on data from the
database maintained by Network #1. Network #1 staff analyzed the data. The
Network maintains a database called Standard Information Management System
(SIMS) that tracks the number of patients starting PD as well as patients
leaving PD therapy due to transfer to HD, transplantation, or death. The
database also includes patients' race, gender, age, and the presence or
absence of diabetes at the start of ESRD. The data used for this study
included incident ESRD patients starting PD therapy between 1 January 2001 and
31 December 2005. Patients were determined to be incident PD patients
immediately after they completed a PD training program or transferred to PD
from HD within 3 months of initiation of dialysis. Mortality was calculated
based on the deaths reported in this database. Limited comorbidity data were
available on the patients, making it difficult to examine the impact of
comorbidities on outcomes.
Centers were arbitrarily grouped by the number of PD patients cared for by
the facility as of December 2005: group A centers cared for 25 patients or
fewer per center and group B centers cared for more than 25 patients per
center. Patient-specific data were combined for patients cared for in each of
the two groups. The total number of centers in the study was 105, with 91
centers in group A and 11 centers in group B. The number of incident patients
in group B averaged 106 (range 46–214) over the 5-year study period. The
number of prevalent patients in group B as of December 2005 ranged from 26 to
98, with a mean of 46. Specific end points included transfer to HD,
transplantation, and death. The number of patients either remaining on PD
therapy or reaching a specific end point was noted at the end of each year
after enrollment. The total numbers of deaths and transfers to HD after the
original incident PD patient started PD were determined for year 1 and year 2
for each group. Death rates and technique failure rates were calculated at the
end of year 1 and year 2 for each group. Mortality was calculated based on
deaths that occurred while on PD and during the subsequent 60 days after
transfer to HD. Technique failure rates and mortality rates were defined as
follows:
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The number of patients was adjusted for transplantation and patients moving
out of the area by censoring these patients. The data were analyzed using the
SAS software (SAS 9.1.3; SAS Institute, Cary, NC, USA) and differences between
the groups were calculated using the chi-square.
The sample size calculation for this study was based on a power analysis
that assumed a 25% survival or technique failure benefit in the larger centers
compared with the smaller centers. On the basis of the USRDS 2007 database
(adjusted first year PD mortality for 2004 of 16.5%), we calculated that a
sample size of 2280 would be needed to detect an absolute survival difference
of 25%, assuming a power of 80% and a two-tailed alpha level of 0.05.
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RESULTS
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There were 5003 patients in the study. A total of 3025 were included in
group A and 1978 patients were in group B. The baseline characteristics of the
study population are summarized in Table
1. There was a similar proportion of males and females in both
groups. In both groups the majority of the patients were white. There was a
higher percentage of patients with diabetes mellitus in group B although the
difference was not statistically significant. The average age in both groups
was similar. At the end of year 1, 1843 patients remained on PD in group A and
1165 patients in group B; at the end of year 2, 1182 patients remained on PD
in group A and 813 in group B (Figure
1).
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Figure 1 — Number of patients by peritoneal dialysis center size: centers with
25 patients (Group A); centers with >25 patients (Group B).
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Table 2 shows the
relationship between center size and mortality and technique failure. For all
patients, death and technique failure rates were 14.3% and 14.2% during year 1
and 15.4% and 13.0% during year 2 respectively. As shown in
Figure 2, there was a
statistically significant higher technique failure rate in group A than in
group B for both year 1 [odds ratio (OR): 1.36, p = 0.005 and year 2
(OR: 1.35, p = 0.03). There was no statistical difference in
mortality rates (reported as deaths) between the groups for year 1 or year 2
(Figure 3).
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Figure 2 — One- and 2-year technique failure rates for peritoneal dialysis
centers with 25 patients (Group A) and >25 patients (Group B).
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Figure 3 — One- and 2-year mortality rates for peritoneal dialysis centers
with 25 patients (Group A) and >25 patients (Group B).
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DISCUSSION
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The present study demonstrates that technique failure rates were
significantly higher in PD units with 25 patients than in units with
>25 patients at the end of both year 1 and year 2. The calculated rates of
technique failure were 31% higher during year 1 and 30% higher during year 2
in small centers (group A). However, death rates were not significantly
different between the two groups (p = 0.53 and p = 0.41 for
years 1 and 2 respectively). Importantly, more PD patients in Network #1
receive care in smaller centers (25 patients/center) than in bigger
centers. African-Americans have a lower mortality on PD but a higher technique
failure rate on PD
(1,12–14).
The study population was mostly white but group B had a higher percentage of
African-Americans than group A. We do not think that this had an impact on our
study results because, despite the larger percentage of African-Americans and
patients with diabetes mellitus, group B had a lower technique failure rate
than group A.
Our results are consistent with prior studies comparing center size and
technique survival. In a review of the Netherlands dialysis database (RENINE)
(8), Huisman et al.
found that mean annual technique failure rates correlated with the number of
patients on PD in a center (r =–0.396, p = 0.009) and
with the fraction of patients on PD (r =–0.410, p =
0.006). They also showed that having fewer than 20 patients per unit was
associated with a higher risk of technique failure (relative risk 1.68). As in
our study, there was no difference in survival between small- and large-center
groups. Similarly, in a review of the Baxter database consisting of three
large cohorts of patients initiating PD in 1999–2001 (total of >30
000 patients), Guo and Mujais observed that centers with fewer than 20
patients had a higher technique failure rate than centers with more than 20
patients (hazard ratio 1.130, p < 0.0001) but had no difference in
mortality (10). Schaubel
et al. reviewed data from the Canadian Organ Replacement Register
(CORR) and evaluated the effect of center characteristics on mortality and
technique survival by center-specific cumulative number of PD patients treated
using data on 17900 patients that received PD from 1981 to 1997
(9). They found that, as the
cumulative number of patients treated by a PD unit increased,
covariate-adjusted mortality decreased (p = 0.05) and that, as the
percentage of patients starting PD in a unit increased, technique failure
rates decreased.
The reasons for the relationships between center size and technique failure
are not clear. It has been suggested that the difference in technique failure
rate might be related to having more experience in managing PD patients and
the complications of PD therapy, having more staff available for patients, and
responding to problems in a more timely manner. If these reasons are correct,
then the reason for the lack of difference in mortality rates between larger
and smaller groups is not obvious. The reason could be that the SIMS database
(used in the present study) consists of all events in chronological order that
allowed the attribution of death to either PD or HD, based on the time when
death happened relative to change in modality. In our study, we attributed
death to PD for up to 60 days after transfer to HD. This method of calculating
mortality rates when dealing with technique failure was previously used by
Collins et al. (3).
The method seeks to avoid deaths that should be attributed to PD but that
occur shortly after switching to HD.
Our study has some limitations. It is a retrospective study and therefore
subject to unmeasured confounders. Also, the information used is strictly
limited to information available in the Network database and does not include
several important variables, such as additional patient demographic data, the
nurse-to-patient ratio in each group, and the degree of PD specialization,
that is, the proportion of PD to HD patients in each group or center. The data
are also reflective of just one ESRD network in the USA and, while they may be
used as a guide to other networks, they may not reflect the characteristics of
other networks. Patient outcomes in the study could not be accurately adjusted
for comorbidities since limited comorbidity data were available. Another
limitation is the arbitrary use of a cutoff number for small centers (25
patients). There are no studies determining the exact number of patients per
center at which there is a difference in patient-related outcomes. Previous
studies have used an arbitrary number of 20. It is possible that the
difference is a continuous one, with better patient outcomes with increasing
center size, as shown by Schaubel et al.
(9). Our study set an arbitrary
cutoff number of 25 patients prior to collection of data. An attempt to
analyze the centers based on increasing size would result in very small
patient numbers that would not be significant to make reliable
conclusions.
In summary, the present study shows that centers with a smaller number of
PD patients have a significantly higher technique failure rate compared to
larger centers but that there is no statistically significant difference in
mortality rates. Despite the limitations of the study, the results are
consistent with previous studies and therefore suggest that the effect of
center size on technique failure rates should be taken seriously. It is
concerning that the majority of PD patients in Network #1 receive care in
smaller centers; this observation is consistent with the trend in other parts
of the USA. A review of the Baxter database, consisting of four large cohorts
of patients initiating PD in 2000–2003 (total of >40 000 patients),
revealed that more than 80% of centers have fewer than 20 patients on PD
(15). While encouraging
smaller centers to develop PD therapy to broaden its geographic distribution
and make it more available to a wider range of patients, the association with
higher PD technique failure rates requires that smaller centers carefully
examine their treatment regimens and consider building up their practice or
consolidating with other smaller centers to improve patient outcomes. Perhaps
a nationwide study looking at technique failure rates and mortality among
centers will have sufficient numbers to permit comparing centers with
incremental numbers and may be beneficial in determining the minimum center
size required to achieve optimal technique and patient survival on PD.
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DISCLOSURE
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The analyses upon which this publication is based were performed under
contract number HHSM 500-2006-NW001C, entitled End Stage Renal Disease
Networks Organization for the State of Connecticut, sponsored by the Centers
for Medicare & Medicaid Services, Department of Health and Human Services.
The content of this publication does not necessarily reflect the views or
policies of the Department of Health and Human Services, nor does mention of
trade names, commercial products, or organizations imply endorsement by the US
government.
The authors assume full responsibility for the accuracy and completeness of
the ideas presented. This article is a direct result of the Health Care
Quality Improvement Program initiated by Centers for Medicare & Medicaid
Services, which has encouraged identification of quality improvement projects
derived from analysis of patterns of care, and therefore required no special
funding on the part of this contractor. Ideas and contributions to the author
concerning experience in engaging with issues presented are welcomed.
Received 5 May 2008;
accepted 7 August 2008.
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ABSTRACT
PATIENTS AND METHODS
