Association for Molecular Pathology


February 2011, Volume 17, Number 1


From the Coding and Coverage Corner

By Jeffrey A. Kant MD PhD

Medically Unlikely Edits (MUEs):
MUEs are ‘edits’ that are applied to individual lines of a claim form for a specific CPT code to decide whether that line will be paid or not, depending on whether the number of reported units of service exceeds the allowable MUE. The term ‘MUE’ was originally proposed by CMS as “medically unbelievable edit,” such as two appendectomies for a patient on the same date of service! To reduce paid claims error rates. Another intent of MUEs was to catch typographical errors that made no sense (e.g. 30 or instead of 3). This program was presumably felt to be important for payment integrity because, for reasons of efficiency, reimbursement claims are typically handled electronically supplemented by algorithms to evaluate conformance with a payer’s coverage decisions. Reviews/audits of services which may occur later more carefully examine issues of medical necessity, appropriate documentation and potential abuse.

MUEs are chosen by the CMS Correct Coding Initiative Contractor, and confidential lists with suggested numbers are circulated quarterly to major professional organizations for comment. How the suggested MUE is selected is unknown, but many feel this is done at least partly on a statistical basis (e.g. the MUE could be set at the 98th or 99th percentile of claims submissions over a prior period of time). Suggestions for revisions (usually upwards) are sometimes accepted, but people experienced in the process intimate that is the exception more than the rule. Not all MUEs are publically known, even after final decisions are made. This reflects the concern of CMS that some providers may ‘game’ the system for services that are more likely to be offered with higher units of service. MUEs of 3 or less (there are some exceptions) are usually published by CMS. Codes without a published MUE likely have one! You can see the most recently updated list of published MUEs on the CMS website: (

In this fashion legitimate units of service for moderately complex (and almost certainly more complex) molecular services are likely to run afoul of MUEs. Take, for example, DNA sequence analysis of a 60 exon gene. Submission of 83898 for amplification of each exon unit is likely to exceed the MUE. A potential work-around is most MUEs can be billed with a modifier, so in the aforementioned situation the amplification services could be reported on separate lines of the claim form, 30 units without a modifier and 30 units with a modifier on a second line. Even then it is very possible each line will exceed an unpublished MUE for this CPT code, and payment would be denied for this code.

A particularly troublesome MUE is the published limit of one (1) for 83912, Molecular diagnostics; interpretation and report. CMS appears to believe that interpretive work for ALL services in oncologic or heritable disorders performed on a single date of service must be lumped. Those interpreting independent factor V Leiden and Prothrombin gene mutation assays, or immunoglobulin and T-cell receptor gene rearrangement studies, readily appreciate this assumption not only does not make sense but is unfair and inconsistent when compared with payment for other laboratory interpretive services, e.g. immunohistochemistry, each antibody (88342).

One lives and learns in the area of MUEs. There is a ‘little-used-to-date’ (because the overall program is new) process to submit MUEs for reconsideration.