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st: Interval censored survival and stpm or intcens


From   Sharon Minnick <slminnick@ucdavis.edu>
To   statalist@hsphsun2.harvard.edu
Subject   st: Interval censored survival and stpm or intcens
Date   Thu, 06 Sep 2007 21:42:19 -0700

Hello,

I have been attempting to analyze my interval censored survival data with either stpm or intcens ado's (From SSC). Both programs have been used in published papers (stpm: Royston and Parmar 2002; intcens: Griffin et al 2006). However, unless I am missing something, they don't seem able to handle multiple records per subject. In my study, subjects are bled and their serology checked at 6 month intervals. I want to be able to use the intervals when they were negative (and at risk) as well as the interval ending in seroconversion (or censoring) and I don't want to make only one interval per subject where some intervals will then be 2 or 3 years long. Does anyone have experience using either of these ado's in such a situation?
My data is in the span format with multiple records per subject. For each subject, _t0 is the first date of the span and _t is the second date of the span. There are no gaps, so _t for the first span is equal to _t0 for the second span.

In the intcens ado, the interval is specified as t0 and t1, there is no subject identifier. Intcens does not use stset parameters so I would lose some of the structure of my data.

For stpm, I have tried to define the left variable to specify that the observations are interval-censored by using _t0 as the left variable (which is < _t so according to the help file, when _d is 0, this will specify late entry at _t0 and right censoring at _t and when d is 1, this will specify interval censoring with an event in [_t0, _t]. I always receive the error message "

If anyone has used these ado files with interval censored data with multiple records per subject, I would appreciate a note as to whether or not it worked (and how to set it up).

Thanks!

Sharon Minnick
University of California at Davis



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