Well understood but the challenge has been that for the same record we are getting the final result by comparing two date fields against a different date range for each. Firstly, we make sure the case was opened within the reporting date range (startdate <= opened_on <= enddate). Secondly, we compare admission date against today's date (e.g. date_admission + interval1 < today < date_admission + interval2). 
Here is a sample key:

"key":["LKO","FZD","11","8da9a9b6eb5a8844d567bed9105ff1e9","needing_follow_up","2013-04-11","2013-04-02"]

( "key":[{region_id},{district_id},{site_number},{user_id},"needing_follow_up", {opened_on} , {date_admission}] )