st: Interval censored survival and stpm or intcens

[Sharon Minnick <slminnick@ucdavis.edu>]

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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