In 2015, the Centers for Medicare & Medicare Services (CMS) established 4 new Healthcare Common Procedural Coding System (HCPCS) modifiers to define subsets of modifier 59 (distinct procedural service). The modifiers are XE, XS, XP, and XU, sometimes listed in policies as X{ESPU} modifiers. Modifier 59 is intended to indicate a separate and distinct service from another service with which it is usually bundled. This modifier is used frequently and sometimes incorrectly to bypass National Correct Coding Initiative (NCCI) edits. For this reason, modifier 59 is among the most frequently audited CPT codes.¹

Modifier 59 Definition in CPT

Proper use of this modifier is explained in CPT: “Modifier 59 is used to identify procedures or services, other than E/M services, that are not normally reported together but are appropriate under the circumstances. Documentation must support a different session, different procedure or surgery, different site or organ system, separate incision or excision, separate lesion, or separate injury (or area of injury in extensive injuries) not ordinarily encountered or performed on the same day by the same individual.” Note that simply having a unique diagnosis for the service is not sufficient reason to apply modifier 59 or 1 of the new X modifiers. Each of the subset modifiers identifies 1 of the indications listed above for modifier 59 and identifies a specific type of distinct procedural service based on site, session, provider, or nonoverlapping services.

Uses of X{EPSU} Modifiers

While modifier 59 is still accepted, providers are advised to use a more specific X modifier if appropriate (Table 1).² Either 59 or the appropriate X modifier is used in circumstances in which the Medicare NCCI edits, or the CPT “separate procedure” rule, should not apply, and separate reimbursement is justified by Medicare’s instructions and criteria.³ Illustrative cases for each X modifier are listed below.

• XE separate encounter: A service that is distinct because it occurred during a separate encounter (think E for encounter). A separate encounter involves a separate visit or session on the same day by the same provider or providers of the same group. For example, NCCI edits bundle gonioscopy (92020) with laser trabeculoplasty (65855) because a goniolens is used to deliver the laser energy to the trabecular meshwork. Gonioscopy performed in-office as part of the eye exam that determined the need for laser is billable with modifier XE when the laser procedure is performed later the same day in another location, an ambulatory surgery center, by the same physician.
• XS separate structure: A service that is distinct because it was performed on a separate organ/structure (think S for structure). Medicare defines a different anatomic site as one that “… includes different organs or different lesions in the same organ. However, it does not include treatment of contiguous structures of the same organ. ... Treatment of posterior segment structures in the eye constitute a single anatomic site.” A contralateral structure supports use of modifier XS. For example, a patient with anatomically narrow angles and elevated intraocular pressures returns for peripheral iridotomy (PI) on the left eye after PI on the right eye 3 weeks ago. During the same operative session, laser iridoplasty (66762) is performed on the right eye due to persistent narrow angles. Because the NCCI edits treat 66762 as an incidental part of 66761 (ie, bundled), modifier XS with 66762 will permit reimbursement, which would otherwise not occur without the modifier.
• XP separate practitioner: A service that is distinct because it was performed by a different practitioner (think P for practitioner). This modifier applies when providers in the same group are involved in the care of a single patient. For example, an optometrist performs gonioscopy (92020) for a patient with open-angle glaucoma who does not tolerate antiglaucoma medications. Later the same day, an ophthalmologist in the same group practice performs laser trabeculoplasty (65855). Because the NCCI edits treat 92020 as an incidental part of 65855, modifier XP with 92020 will permit reimbursement, which would otherwise not occur without the modifier.
• XU unusual nonoverlapping service: The use of a service that is distinct because it does not overlap usual components of the main service (think U for unusual). No illustrative ophthalmic example comes to mind that is not already addressed by XE, XS, or XP.

Conclusion

Modifier 59 (distinct procedural service) is frequently used to negate NCCI edits that bundle services on the same day, but often incorrectly. Consequently, CMS (not CPT) initiated 4 HCPCS modifiers: XE, XS, XP, and XU. While modifier 59 is not deleted from CPT, CMS instructs that these X modifiers should be used preferentially where applicable. The X{EPSU} modifiers provide greater specificity on claims for reimbursement that implicate the NCCI edits and better define the circumstances for separately billing those services. Like modifier 59, they should not be used simply to unbundle codes to garner payment. It is unclear how modifier XU will be used (if ever) in eye care. For further information on this topic, CMS has resources available in an article,⁴ the Medicare Claims Processing Manual,⁵ and a Medicare Learning Network publication.⁶ GP

Editor's note: This article is an update to a previous column in Glaucoma Physician, which is available with additional tables at https://www.glaucomaphysician.net/issues/2017/september-2017/unbundle-modifiers

Kevin J. Corcoran, COE, CPC, CPMA, FNAO, is president of Corcoran Consulting Group in San Bernardino, California.

References

1. Centers for Medicare and Medicaid Services. CMS transmittal 1422, specific modifiers for distinct procedural services. August 15, 2014. Accessed November 9, 2020. http://www.cms.gov/Regulations-and-Guidance/Guidance/Transmittals/Downloads/R1422OTN.pdf 
2. Moda health reimbursement policy. October 8, 2014. Accessed November 9, 2020. https://www.modahealth.com/pdfs/reimburse/RPM027.pdf 
3. American Medical Association. NCCI policy manual for Medicare services, Chapter 1: general correct coding policies for national correct coding initiative policy manual for Medicare services. Available at: https://www.cms.gov/Medicare/Coding/NationalCorrectCodInitEd/NCCI-Manual-Archive
4. Centers for Medicare and Medicaid Services. Modifier 59. Accessed November 9, 2020. https://www.cms.gov/Medicare/Coding/NationalCorrectCodInitEd/downloads/modifier59.pdf 
5. MCPM chapter 23 §20.9.1.1 instructions for codes with modifiers. Accessed November 9, 2020. https://www.cms.gov/Regulations-and-Guidance/Guidance/Manuals/downloads/clm104c23.pdf 
6. Centers for Medicare and Medicaid Services. Specific modifiers for distinct procedural Services. Accessed November 9, 2020. https://www.cms.gov/Outreach-and-Education/Medicare-Learning-Network-MLN/MLNMattersArticles/Downloads/MM8863.pdf