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I found Nicks comment on the PharmPK Discussion - Calculating GFR forum.
I am a bit of a beginner with posts and thought I might e-mail. I am
looking at comorbidities in lung cancer and trying to assess renal and
hepatic function. I was thinking of looking at converting my
creatinines to creatinine clearances and then possibly converting them
to standardised 1.73m2.
How do I do a 3/4 power. Is it just the calculated CC eg Cockcroft and
Gault to the power of 3/4 i.e CC^.75 or is there another trick?
Looking forward to your reply
Geoff
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Geoffrey,
> I found Nicks comment on the PharmPK Discussion - Calculating GFR
forum.
> I am a bit of a beginner with posts and thought I might e-mail. I am
> looking at comorbidities in lung cancer and trying to assess renal
and
> hepatic function. I was thinking of looking at converting my
> creatinines to creatinine clearances and then possibly converting
them
> to standardised 1.73m2.
I don't know exactly which discussion thread you are referring to. Can
you explain more clearly why how you propose to use renal function as a
co-morbidity of lung cancer?
Using 3/4 power is an allometric scaling method which can be applied to
get suitably scaled estimates of creatinine clearance. But it is not yet
clear to me what you want to do and so I cannot help you with the
allometric scaling yet.
Nick
--
Nick Holford, Dept Pharmacology & Clinical Pharmacology
University of Auckland, 85 Park Rd, Private Bag 92019, Auckland, New
Zealand
n.holford.-at-.auckland.ac.nz
www.health.auckland.ac.nz/pharmacology/staff/nholford
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The following message was posted to: PharmPK
Geoffrey,
If you want to estimate the clearance of a drug entirely eliminated by
the
kidneys (or you have a model with a renal elimination component) then I
would use an uncorrected measure/estimate of CrCL (i.e. in units of
volume/time). This has information on both renal impairment and size
already (in individuals with normal renal function, smaller ones will
have
lower CrCLs than bigger ones). So actually the relationship between
renal
clearance (CLR) and CrCL should be linear and could be standardised:
CLRindividual = CLRstandard*(CrCL/medianCrCL)
If you are comparing renal function between individuals of different
sizes,
then it would be sensible to standardise estimates with size in a
nonlinear
way (I would go for surface area in adults if you have a narrow (2-3
fold)
weight range, otherwise maybe wt^0.75).
Joe
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