Hi @ed_sas_member , I am not actually losing any information since that is a duplicate entry. They might have entered multiple entries for the different drug codes. They initially might have a drug code 'A' program but in between they might have shifted to new drug_code 'B' for few months and they might come back again to Drug code 'A' program. Effective run date tells us which is the latest entry in the system since those are updated after 6 months to 1 year of actual program enrollment dates. e.g. for patient 699 -> I will lose the drug intake of drug BB between nov 2015 and dec 2015, because same person cannot have more than more than one drug at same span. Nov and Dec 2015 are captured by the first record with latest entry date which means that the first record is true for nov and dec 15. you might have question on how can two drug codes can be at same effective date. (Current system captures the date but not the timestamp for the entries, it might change in future but we have very less cases of same effective dates compared to millions of overlap date ranges).
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