st: STATA 10: Obtaining and comparing C-statistic in Left Truncation, among nested models

[Diego Bellavia <messadua@yahoo.it>]

Hi all, 

I have performed a survival analysis deploying Cox Models, correcting for left truncation (time of diagnosis and time of enrollment into the study are not equal). I have built few models with a nested strategy (first model: group of variables A as potential predictors, secondo model: A + B, third model A + B + C etc...). 
Now, when I use the following command to get the C-stat in STATA 10: 

          estat concordance, noshow 

I get the following error message: "estat concordance may not be used with late entry or time-varying data", that I cannot overcome 

Anyone here knows whether there is a way to obtain C-stat and compare different C-stats among different (nested) Cox models in STATA 10, after correcting for left truncation ? 

Thank you in advance, 

Diego


      

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