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Article Review/Hyperlink
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Feldman HI, Kinosian M, Bilker WB, Simmons C, Holmes JH,
Pauly MV, Escarce JJ
Effect of dialyzer reuse on survival of patients treated
with hemodialysis
J Am Med Assoc
(Aug) 276:620-625 1996

The authors report that patients new to dialysis in the years 1986 and
1987, and dialyzed in free standing facilites that reprocessed their
dialyzers with Peracetic/Acetic Acid (PA/A) had a higher probability of
death than other patients.
The authors used the Medicare PMMIS data base and the Centers for Disease
Control annual facility survey for their data. They assumed for their
primary analysis that patients once assigned to a facility that reported
reuse of dialyzers, that the patient was consistently and continuously
"exposed" to reuse ("intention to treat" assumption). They used a Cox
model to define relative risks of death. Other covariables were age, sex,
primary diagnosis, and race. They looked at two models. The first had
reuse (yes or no) and all three types of sterilants (peracetic acid-hydrogen
peroxide-acetic acid (PA/A), formaldehyde,
and glutaraldehyde) in the equation. The second had only reuse (yes) and
the three sterilants.
For both models, the risk of PA/A reuse was only significant in the free
standing facilities. In the first model, there was a 10% increase in the
relative risk of death (CI 1.01 - 1.18, p = .02) for patients dialyzing in
free standing facilities using PA/A vs. no resuse. In the second there was
an 8% increase in the relative risk of death (CI 1.01 - 1.14, p = .02) for
patients dialyzing in free standing facilities reprocessing with PA/A vs.
formaldehyde or glutaraldehyde.
In their sensitivity analysis, the authors "undid" the intention to treat
assumptions and censored patients when they moved to a different dialysis
unit. The relative risk persisted for PA/A reuse in free standind dialysis
units.
The expected impact of race, age, diagnosis, and sex was seen in both their
models. There was a slight improvement in survival in free standing
facilities where there was "more frequent" water system disinfection and
where reuse was an automated procedure.
Comment: The most significant aspect of this report is that it
validates the
findings of Held and colleagues (AJKD,23:692-708, 1994). It uses a larger
data set and comes to essentially the same conclusions. Held's data
referred to prevalent patients in 1989 and 90 followed for one year. This
data referred to incident patients followed from 1986-7 to death,
transplant, change to PD, or June 30, 1991. The time frames overlap, so
assumptions about dialysis technology, and dialysis adequacy would be
similar.
Since 1992, when the preliminary report of Held's study was
published, there has been a significant improvement in the design,
surveillance, and practice of reuse. It is not possible to extrapolate the
relative risk from the Feldman study to current practice since much has
changed in the industry both in the delivery of dialysis and the practice
of reuse. Since the delivery of dialysis has an important and measureable
impact on survival, it would be necessary to recast the Cox model to
include that covariable to see if the reuse effect is still significant.
Feldman's data is reported at the facility level. The authors do not
know with certainty that a given patient was actually "exposed" to reuse,
but only that the patient was dialyzed in a facility reporting the practice
of reuse. They do not know what average reuse numbers were, what the
dialyzer was, what the causes of death were, or what the dialysis
prescription or delivery were. Finally, since they do not report the R
squared values, it is not possible to know how much of the variation in the
survival remains "unexplained" by their models.
Feldman does explain the cause of their observation, but argues for
the statistical validity of the association. He does not explain why the
effect is not observed in hospitals. He suggests that the co morbidity is
higher in hospitals so the reuse effect is not discoverable. He does not
however provide standard mortality ratios for comparison. Feldman's study
has a smaller number of patients on reuse in hospitals than in the free
standing units so it may lack sufficient power to find a difference if it
exists, though he does not provide a power analysis.
That the authors are not able to explain the effect does not vitiate
their study. It is as important to understand the "fact" of this effect as
it is to understand the "why" of this effect. The "fact" is that practices
like reuse that are widely applied in an inconsistent manner can have
important consequences on patient survival. More importantly, it takes
large numbers of patients studied over years to detect this impact. In the
average sized dialysis facility with about 70 patients and a crude
mortality of 20% (14 deaths) an 8% increase in mortality would result in
only 1 additional death.
This study reinforces the importance of the recommendations made by
the manufacturer of PA/A and of AAMI to validate and document each step in
the reuse process. It also reinforces the observation that there are
facility based "risk" factors for mortality.
The application of reuse may only be an "indicator" of facility or
corporate policies and procedures that have the unintended effect of
increasing patient mortality. This study is a strong argument for
facilities and dialysis corporations to cooperate in large data bases that
allow the review of industry wide practices in a statisically powerful and
timely manner. It took 6 years from the end of the Feldman study for the
results to be published on a cohort of patients who started dialysis 10
years ago. What unexpected effects are we going to be reviewing in 2006
about our patients starting dialysis in 1996? (Peter B. DeOreo MD, Case
Western Reserve
University, Cleveland)
The full abstract is available at
the JAMA site. You will need to
register with the JAMA before being allowed to access this
material.
Once you have registered, click on the links below:
Abstract
Press Release
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