A longitudinal database of de-identified patient healthcare transaction
data records linked by longitudinal linking tags (IDs) is provided. A new
healthcare transaction data record, which may include alphanumeric
identification code attributes, third party attributes and/or demographic
attributes, is assigned an linking ID associated with a previous
healthcare transaction data record based upon successful comparison of
either a designated set of identification code attributes or a designated
set of demographic attributes. The longitudinal data base is assembled by
a matching process in which a new data record is compared level by level
with previous healthcare transaction data records through a hierarchy of
a first series of matching levels each defined by a designated set of
alphanumeric identification code attributes and a second series of
matching levels each defined by a designated set of attributes including
demographic attributes and then assigned the ID associated with a
successfully matched reference data record.