Pathology/Lab Coding Alert

Question: Could you please clarify what “MUE” is and how it might impact my coding?

Codify Subscriber

Answer: “MUE” is an acronym for medically unlikely edits, which the Centers for Medicare & Medicaid Services (CMS) established as a unit-of-service edit for HCPCS Level II and CPT^® codes. An MUE is assigned to a specific code to represent the maximum number of units of the code that you should report — either on a specific claim or on a specific date.

CMS developed the edits to reduce the paid claims error rate for Medicare claims.

Exceptions: When a provider legitimately exceeds the MUE frequency limit, Medicare has provided guidance for how to override an MUE value, using “distinct service” modifiers, such as 59 (Distinct procedural service) or the following X{EPSU} modifiers:

• XE (Separate encounter …)
• XP (Separate practitioner …)
• XS (Separate structure …)
• XU (Unusual non-overlapping service …)

Although Medicare had introduced a specific modifier, GD (Units of service exceed medically unlikely edit [MUE] value and represent reasonable and necessary services), the agency never provided instruction for using the modifier and deleted it from HCPCS Level II in 2020.

Alert: The MUE table includes a column for “MUE Adjudication Indicator” (MAI), which provides guidance about what circumstances allow you to override an MUE limit for a given code.

If the code has an MAI of “1,” the code is adjudicated on a claim-line basis, meaning that you can’t exceed the number of MUE units on a claim line. You are allowed to use one of the distinct-service modifiers to override the edit, if circumstances warrant.

An MAI of “2” means that the frequency limit is absolute for a date of service — you cannot override the edit with a modifier.

An MAI of “3” means that the frequency limit is based on the date of service, and Medicare will automatically deny any claims in excess of that limit, even if you use an appropriate modifier. However, Medicare will consider an appeal with appropriate documentation.