New XE, XP, XS and XU modifiers

CMS introduced four new HCPCS modifiers, -XE, -XP, -XS and -XU. These modifiers are collectively known as “-X{EPSU} modifiers”. Humana plans accept HCPCS modifiers -XE, -XP, -XS, and -XU as of 1/1/15. Each of these modifiers should only be used to accurately describe the service that occurred. Until CMS determines when these modifiers must be used in place of modifier -59, Humana will accept either modifier -59 or one of these modifiers accurately appended to a service code.

Source: https://www.humana.com/provider/medical-providers/education/claims/payment-policies/