During the follow-up time, event A will happen multiple times, and there are 3 types of A, I call it A1, A2 and A3. I wonder if there is a statistical method that I can calculate the incidence rates of A1, A2 and A3 separately and compare the incidence rate to each other?
Should I only consider A1 as the event of interest, and consider A2 and A3 as no event, then the incidence rate be N of A1 events/total Person-years during follow-up? And for A2, incidence rate is N of A2/total person-year during follow-up? Would it be problematic that the denominators are the same? How can I compare them?
Thank you so much for your input, Bernhard! I have provided more details as below:
Please give more information on A. Can one person have more than one event A?
Yes, one person can have more than one event A during follow-up.
Can they have different types of A at once or consequently?
They can only have one type of A at each time but could have different types of A during follow-up.
Can a patient have more then one A per year?
In our data, there is no such case, but theoretically patient can have multiple A in one year.
Maybe we can model this as a binomial experiment where each person-year comes with the same probability of each A? Then a proportions test would be the obvious choice. Are the person-years censored (like: Wie have some individuals with 20 person-years observed an some with only 2 person-years observed)? That would draw things towards survival models
*Yes, person-years could be censored, and some patients have quite short follow-up time.