Which item fulfills the minimum information to uniquely identify a patient in the master patient index?

• A. A unique patient identifier
• B. The patient's full name only
• C. The patient's address
• D. The patient's date of birth only

Answer: (A)

A master patient index relies on a single, stable key that uniquely distinguishes one patient from all others. A unique patient identifier serves this purpose because it is specifically assigned to one person and remains constant across systems, providing an unambiguous link to that patient’s records. Full name, address, or date of birth can be shared by many people or change over time, which means any of these on its own could lead to confusion or mixed records. While these attributes may help in confirming identity when used together, they do not guarantee uniqueness the way a dedicated identifier does. Therefore, the minimum information needed to uniquely identify a patient in the MPI is the unique patient identifier.