Hi, I am trying to use PROC GENMOD to fit a multinomial logistic model accounting for repeated measures using GEE. I have a categorical exposure with 3 categories and an ordinal outcome with 3 levels (low, medium, high). However, these exposures and outcomes result from pairwise comparisons between all individuals in my dataset so my unit of analysis is a pair, not an individual. The data table structure is as follows:
| pair | sample1 | sample2 | exposure | outcome |
| 1 | A | B | category 1 | low |
| 2 | A | C | category 1 | medium |
| 3 | A | D | category 2 | high |
| 4 | B | C | category 3 | low |
| 5 | B | D | category 3 | low |
| 6 | C | D | category 2 | medium |
In this simplified example, there are a total of 4 samples (A,B,C and D) so 6 pairs when comparing each sample to all others. I want to account for the fact that each of these samples occurs in multiple pairs, however, I cannot figure out how to deal with the fact I have 2 samples per pair that I need to account for. I have used the following code to incorporate just sample1 as repeated measure, but is there a way to incorporate both sample1 and sample2 as the subject of the repeated measure? I receive various errors whenever I try to do so.
proc genmod data=my_data;
class exposure sample1;
model outcome= exposure / link=cumlogit;
repeated subject = sample1;
run;
Is there a way to accomplish this task?
