Which piece of information is NOT considered individually identifiable health information?

Individually identifiable health information is defined as any data that relates to a person's health status, healthcare provision, or payment for healthcare that can be linked to an individual. The key concept is whether the information can be used to identify a specific person.

The first choice, a diagnosis, is considered individually identifiable health information because it relates directly to a person's health condition and can potentially be linked to that individual when combined with other identifiers.

Social security numbers and dates of birth are also classified as individually identifiable, as they are unique identifiers that can directly link health information to a specific person.

Health treatment status pertains to the care a person has received, which also qualifies as individually identifiable health information, as this data is often linked to an individual’s health record.

Hence, the selected answer is correct because it most closely fits within the context of information that does not distinctly identify an individual unlike the other options. A diagnosis typically requires context or additional identifiers to ensure that it cannot be linked back to a specific individual, thus making it less categorically identifiable compared to the other options.