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Article Review/Hyperlink
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Gotch FA, Levin NW, Port FK, Wolfe RA, Uehlinger DE
Clinical outcome relative to the dose of dialysis is not what
you think: the fallacy of the mean
Am J Kidney Dis
(Jul) 30:1-15 1997

Urea kinetic papers are not usually very clear, so I'll summarize this one in
a nutshell.
Suppose that mortality at Kt/V at 0.8 is way higher than at 1.0, but then is
completely
level beyond 1.2. Now suppose the mean Kt/V in your unit is 1.0, and you
bring everyone
up to 1.5. You see a decrease in mortality. You publish a paper, saying
that a Kt/V of
1.2 is not good dialysis; you must keep people at 1.5.
This is the fallacy of the mean. When the mean Kt/V in your unit is 1.0, you
have a
substantial number of patients on the Bell curve getting Kt/V's of 0.8 and
less. When you
drive everyone up to 1.5, then the number of people sitting on the lower part
of the Bell
Curve is the same, but now these people are up around 1.1-1.3, and not at 0.6
to 0.8.
In fact, this is what happened. Parker and Hakim published such a paper,
noting a
decrease in mortality when they increased Kt/V in around this range. Gotch
argues that
this does not mean a Kt/V > 1.2 (and we're talking single-pool, here),
means lower
mortality. He elegantly goes through a number of studies showing why
decreased mortality
at high mean Kt/V levels can be explained even if the mortality curve is flat
beyond 1.2-
1.3 single-pool Kt/V units.
(John T. Daugirdas, M.D., University of Illinois at Chicago)
The abstract of this paper is available from the AJKD online
at this site.
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