Final answer:
XE, XS, XP, XU are HCPCS modifiers used in medical billing to convey that a service was altered in a specific way, impacting reimbursement.
Step-by-step explanation:
XE, XS, XP, XU are types of Healthcare Common Procedure Coding System (HCPCS) modifiers. These HCPCS modifiers are used in medical billing to indicate that a service or procedure has been altered in some way without changing the definition of the original code. They provide additional information to the payer about the service performed and impact reimbursement processes. For example, modifier XS signifies a separate structure, modifier XP denotes a separate practitioner, modifier XE indicates a separate encounter, and modifier XU signifies an unusual non-overlapping service.