Hello,

I have to set the index date for a disease which definition is based on recurrent symptoms, for example a "recurrent asthma" definition based on asthma diagnosis + at least 2 asthma crisis/year in 2 consecutive years. In this case, the index date has to be set at the date of the first crisis of the series or at the 2nd crisis of the second year?

What do you think is more appropriate? Do you have any published example ?