HCPCS Modifier SA

I know of a practice who is using the SA modifier for an APRN. They are using this modifier on all routine office visits. I would like to know if this is the correct way to use this modifier? If not, in what ways would it be used?

re: HCPCS Modifier SA

Used for (non-surgical) by aprn, pcns and rncs under physician supervision.
"Nurse practitioner rendering service in collaboration with a physician." If the APRN is doing the visit then you're using it right.