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FW: st: Difference between the results of lroc after logistic regression and roccurve/rocreg with covariate adjustment


From   Muhammad Riaz <riaz_stata@live.co.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   FW: st: Difference between the results of lroc after logistic regression and roccurve/rocreg with covariate adjustment
Date   Sun, 16 May 2010 12:56:31 +0100


----------------------------------------
> From: riaz_stata@live.co.uk
> To: statalist@hsphsun2.harvard.edu
> Subject: st: Difference between the results of lroc after logistic regression and roccurve/rocreg with covariate adjustment
> Date: Sun, 16 May 2010 11:02:18 +0100
>
> Dear all,
>
> I am adjusting for the covariates effect in ROC curve analyses. I was thinking to use logistic regression with covariates entered into the model and then use the lroc command to get the adjusted estimate of AUC and ROC curve.
>
> However the google search introduce me to roccurve and rocreg commands and correct methology for covariate adjustement in ROC analyses.
>
> I used both of the commands (i.e lroc and roccurve) and got very different values for area under the curve.
>
> (i.e. 0.85 from lroc after logistic regression with covariates in the model, and 0.52 from rocreg (coeff: of alpha_0=0.52))
>
> My understanding is that "lroc" is measuring the predictiveability of the logistic regression and rocreg measure the predictiveability of the marker in the presence of covariate effect.
>
> However I was thinking that the lroc result of logistic regression without any covariate in the model should be equal to the roccurve/rocreg but it is not? AUC values are 0.68 and 0.61.
>
> Here i dont understand what could be the reason?
> could there be something wrong with roccurve/rocreg command which i dont understand
>
> I will really appreciate your comments and feedback
>
> Thank you in advance,
>
> Muhammad
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