Survival analysis: how do i include a random effect and interval censoring?


New Member

I'm trying to use some form of survival analysis (e.g. accelerated failure time or proportional hazards) to study seed germination time. My data is interval censored (also called "grouped-time") and has a random effect (also called "frailty"). How can I do this, ideally in SAS?

My seeds were on petri dishes that were censused on day 1, 3, 5, 8, and 14. These are interval censored, with a seed that germinated on d8 really germinated between day 6 and day 8. PROC LIFEREG can handle interval censoring, but as far as i know, it doesn't handle random effects. Seeds on the same petri dish are not independent, so I need to be able to include the dish as a random effect.

Is there an approach that allows interval censoring as well as random effects? If so , how should I modify the SAS code below to include random effects? Can I do this in PROC NLMIXED? What is the best/easiest software to do this?

PROC LIFEREG DATA=survGeno2 plots=probplot;
TITLE "Interval censored AFT";
CLASS geno;
MODEL (start,fin)=geno;