Thirty-two states have registries that track the number of people with HIV. States use these registries to learn the extent of the epidemic and how to best allocate resources for its prevention and treatment. Of those states, all except Maryland place full names in their registry. In Maryland, a unique identifier (UI)—an alphanumeric code that is based on the patient’s Social Security number, date of birth, gender, and race—is used instead of a name. While advocates of civil liberties have lauded Maryland’s approach, other organizations question the effectiveness of UI systems.

According to the American Civil Liberties Union (ACLU), name reporting can discourage AIDS testing. In an October 1997 report, the ACLU notes: “One study found that over 60% of individuals tested anonymously would not have tested if...