Rodby RA, Firanek CA
A re-evaluation of PET determined patient solute transport
group classifications
Am Soc Nephrol
J Am Soc Nephrol (abstract)
(Sep) 7:1433 1996
The authors first recall, that using the classification of PET according to
Twardowski, and assuming a Gaussian patient distribution, we would expect
that
approx. 33% of patients should be low average (LA), 33% High average (HA),
17%
high (H) and 17% Low (L).
To determine if their patients were similar to those that defined the PET
groupings, they reviewed the 153 initial Standard PET tests done in their
PD program. All patients were adults and PET tests were not done within 2
months
of an episode of peritonitis. The mean 4-hour D/P creatinine ratio in
their patients was 0.71 +/- 0.10 (median = 0.69, mode = 0.72). This
compared to a mean of
0.65 +/- 0.15 as determined by Twardowski et al, and indicates that their
patients had higher mean solute transport rates and tighter ranges within
transport groups than previously reported.
Only 1.3% of their patients fell
into the previously described L range, with 24.8% LA, 50.3% HA and 17.0% H.
Using their data they would redefine the groups by the 4-hour D/P
creatinine ratio of: L <
0.61, LA 0.61 to 0.71, HA 0.71 to 0.81, and HA > 0.81. Doing this they
found 16.3% of patients were in the low transporter group L, 34% were LA,
30.1% were HA, and 19.6% were H (high transporters), a Gaussian
distribution.
They conclude that the 4-hour D/P creatinine ratio ranges that presently
determine PET
transport groupings grossly underestimate low transporters in their
patient population. This could lead to an inappropriate dialysis
prescription in some patients. They suggest that these ranges need to be
reevaluated.
Comment: This study emphazises the fact that peritoneal
tests may vary in their distribution from one center to another, probably
depending on patient selection. Duration of dialysis before the test,
policy concerning the number of hypertonic solutions used, age of patients,
previous peritonitis rates and methodology of testing may all affect the
distribution of results, sometimes with
unpredictable consequences. As a result, comparison from one center to
another is often difficult. However the argument of real Gaussian
distribution in the
patients of the authors (not in those of Twardowski and all) deserves
strong attention and should be considered to redefine normal ranges.
In our experience, the PET test should be used as a general guide to
the prescription, rather than as a precise mean to predict
adequacy of dialysis. In practice every one should define the distribution
of PET tests in their own center, and should be critical of use of this
test to classify patients in terms of permeability when the mean differs
from the median. (Christian Verger MD, Pontoise,
France)
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Am Soc Nephrol
Basic peritoneal dialysis :
PET testing