In CPT® Surgery Guidelines, a "separate procedure" code is used to identify a service that is typically performed as part of a larger procedure and should not be coded separately when it is an integral component of that primary service. However, it may be reported independently if it is performed alone or is unrelated to the primary procedure.

A. is true because a separate procedure may be reported if it is performed independently or is unrelated to the primary procedure.

B. is true, as "separate procedure" codes are not reported in addition to the code for the primary procedure when they are part of the total procedure.

C. is correct because "separate procedure" designation indicates that the service is often part of a more comprehensive procedure but can be reported separately when performed alone.

D. is false because modifier 79 is not used for unrelated "separate procedures." Instead, modifier 59 is typically used to indicate a "distinct procedural service" when reporting a separate procedure that is unrelated to the primary service.

Therefore, the correct answer is D. To identify a service designated as a "separate procedure" that is reported with an unrelated primary service, append modifier 79 to the code.