st: Including left-censored data in survival model

[Heidi <biscotti@gmail.com>]

Hello all,

I'd like to estimate a Cox hazards model with my dataset, but it looks
like a good portion of my observations are left-censored and failed
in/prior to the first period. (I do have the year that they failed,
but no access to data prior to my time 0.) Having checked _st, it
looks like those subjects have already been dropped from the analysis.
However, these left-censored subjects were mostly also in a particular
category, so dropping them has made the other two categories seem much
more likely to fail.

Is there any way to include these dropped censored observations in the
analysis, at least for comparison to the analysis I'm already done?
Additionally, would there be a more appropriate model to examine
hazard ratios in this situation -- I'm reading through Cleves et al's
Intro to Survival Analysis, but have not (so far) found anything that
directly relates to this situation.

Thanks very much in advance!
Heidi
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