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Re: st: Is it valid to use the individual ratios (i.e. Xi/Yi) in the dependent or independent part of a regression model?


From   David Hoaglin <dchoaglin@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Is it valid to use the individual ratios (i.e. Xi/Yi) in the dependent or independent part of a regression model?
Date   Sun, 27 May 2012 00:11:01 -0400

Dear Jinn-Yuh,

In a notation that is customary in survey sampling, X/Y (perhaps more
commonly Y/X) is the ratio of two population totals.  Please tell us
more about the population for which you would like to estimate the
ratio of the population total of urinary albumin to the population
total of urinary creatinine.

If you are calculating ACR for individual patients, and that is the
variable that you are using in your regressions, how are the
population totals related to those regressions?  The relevance of the
biases that you have mentioned to your analysis is not yet clear.  It
would help if you described one of the multiple regression models that
you are using.

David Hoaglin

On Sat, May 26, 2012 at 9:02 PM,  <guhjy@kmu.edu.tw> wrote:
> ACR (urinary albumin creatinine ratio, i.e. urinary albumin [Xi]
> divided by urinary creatinine [Yi]) is used to standardize for urinary
> concentration to ensure comparability of albuminuria among individual
> patients (http://en.wikipedia.org/wiki/Microalbuminuria). I am using
> ACR as the dependent or independent variable in multiple linear
> regressions. However, "ratio of means" and "mean of ratios (ACR
> [Xi/Yi] in this case)" are both biased estimates for the population
> ratio [X/Y] (Mean of ratios or ratio of means or both?:
> http://www.sciencedirect.com/science/article/pii/S0378375801001811).
> In view of these problems and the many pitfalls of ratios mentioned in
> many references, is it better to use X (or Y) to adjust for Y (or X)
> in regressions (despite its clinical usefulness in individual
> decisions)?
>
> Thank you.
> Jinn-Yuh
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