multi level categorical variable in a cox model

#1
Hello everyone,

I would like to know which kind of test of significance do you use for categorical variables with more than two levels in a COX model (as 3 or 4 levels).
SAS supply type 3 test but I don't understand exactly what does that means.

And a second question : What can we do to assess the global interaction with this multi level categorical variables with a continous variable.

Thanks for your help!!
 
#2
Hei again

At least in R it is possible to do post-hoc comparisons of all levels among each other. This tells you which factor level significantly affects survival compared to any other factor level. Based on this you can then provide a ranking of the levels on their influence on survival. To simulate this post-hoc testing you can simply rename your factor levels so that each level is used as "control" once, however, there might be a proper way of doing it in SAS as well.

To your second question I must admit that I have no clue, sorry.

Hope that helped a bit