Which modifier indicates that a procedure was performed independently by a different practitioner?

The correct answer is the modifier XP. This modifier is used in conjunction with a primary procedure code to indicate that a service was performed by a different practitioner and is distinct from the primary service being reported. The use of the XP modifier helps clarify that the services are not being bundled together for billing purposes, promoting transparency in the reported procedures.

The other modifiers listed have distinct meanings that do not relate to the independent practice by a different practitioner. For instance, XE indicates a separate encounter, XS signifies a separate structure, and XU denotes an unusual service. None of these modifiers capture the essence of indicating a procedure done by another individual practitioner as effectively as XP does. This is particularly important for ensuring accurate billing and compliance with coding standards.