ICD-10 Code Z22.322: MRSA Carrier & Colonization – Complete Coding and Billing Guide

ICD-10 code Z22.322 — Carrier or suspected carrier of Methicillin-resistant Staphylococcus aureus — is a billable Z-code used to document MRSA colonization status in patients who harbor the organism without presenting with an active infection. It belongs to ICD-10-CM Chapter 21 (Factors Influencing Health Status and Contact with Health Services), and its correct application depends on a precise understanding of the colonization-versus-infection distinction that trips up even experienced coders.

What Does ICD-10 Code Z22.322 Mean?

Z22.322 identifies a patient as a carrier or suspected carrier of MRSA — meaning the drug-resistant organism is present on or in the body (most commonly the nares, skin, or perineum) but is not currently causing symptomatic disease. The ICD-10-CM Alphabetical Index maps both “MRSA colonization” and “carrier of methicillin-resistant Staphylococcus aureus” directly to this code.

Key attributes of Z22.322:

• Valid and billable for fiscal year 2026 (effective October 1, 2025, per CMS ICD-10-CM FY2026 updates)
• POA exempt — no Present on Admission indicator required for inpatient admissions
• Not acceptable as a principal diagnosis — must be sequenced as a secondary code
• Applicable in all care settings where colonization is documented or clinically suspected
• Grouped under MS-DRG 951 (Other Factors Influencing Health Status)

What Conditions and Presentations Does Z22.322 Cover?

Z22.322 captures the carrier state associated with MRSA — a circumstance influencing health status rather than a current illness. It is appropriate when documentation reflects any of the following:

• A positive MRSA nasal swab screen or MRSA surveillance culture with no clinical signs of infection
• Documented “MRSA colonization” in the provider note, H&P, or problem list
• A positive “MRSA screen positive” result noted by the provider in the clinical record
• Admission screening that identifies MRSA carriage prior to elective surgery or immunocompromised care
• A patient known to carry MRSA who presents for an unrelated condition

What Does Z22.322 Specifically Exclude?

Z22.322 should not be used for these scenarios:

• Active MRSA infection of a known site — use a site-specific combination code such as J15.212 (MRSA pneumonia) or A41.02 (sepsis due to MRSA), plus B95.62 when no combination code exists
• Carrier of viral hepatitis — directed instead to the B18.- code category (Excludes2 note at the Z22 category level)
• Personal history of MRSA without current colonization — use Z86.14 instead
• Resistance to penicillin as a standalone finding — do not report Z16.11 as an additional code alongside Z22.322; this is explicitly unsupported per ICD-10-CM Official Coding Guidelines Section I.C.1.e

When Is Z22.322 the Right Code to Use?

Selecting Z22.322 correctly requires working through a short but critical decision pathway:

1. Confirm the provider has documented colonization, carrier status, or a positive MRSA screen. Coder inference alone is insufficient — the physician or advanced practice provider must explicitly state or acknowledge the finding.
2. Verify no active MRSA infection is present. If the provider documents both colonization and an active MRSA infection at the same encounter, Z22.322 may be assigned alongside the infection code — but the infection code leads.
3. Determine whether “suspected” applies. The code covers suspected carriers — meaning it is appropriate when a positive preliminary culture or screen is noted even before confirmation, provided the clinician documents the suspicion.
4. Check that this is not a historical reference. If the provider documents a prior MRSA infection that has resolved with no mention of ongoing colonization, Z86.14 (personal history of MRSA) is the correct code, not Z22.322.
5. Sequence as secondary. Z22.322 is never the principal diagnosis. Sequence it after the primary reason for the encounter.

How Does Z22.322 Differ From Z22.321 and Z86.14?

In practice, the Z22.321 vs. Z22.322 distinction hinges entirely on sensitivity testing results — the strain designation drives the code. Coders should never default to Z22.322 when susceptibility testing is absent or inconclusive; query the provider for clarification.

What Documentation Is Required to Support Z22.322?

Strong documentation is the single biggest differentiator between a supportable Z22.322 claim and an audit liability. The ICD-10-CM Official Coding Guidelines are explicit that colonization status must be based on provider documentation — not coder assumption from lab results alone.

What Must the Provider Document in the Clinical Notes?

1. Explicit acknowledgment of the MRSA carrier state — phrases such as “MRSA colonization,” “positive MRSA screen,” “known MRSA carrier,” or “suspected MRSA carrier” must appear in the provider’s documentation
2. The clinical setting for the finding — whether identified on admission screening, during a pre-operative workup, or as part of infectious disease follow-up
3. Confirmation that no active infection is present — or, if both colonization and infection coexist, documentation of each condition separately
4. Isolation or infection-control precautions ordered — while not required to justify the code, this entry in the record corroborates the colonization documentation and is a helpful audit defense

Which Lab or Screening Results Support This Code?

Lab results alone do not automatically justify Z22.322 — but they serve as critical supporting evidence when the provider has acknowledged the findings. Relevant supporting results include:

• Positive MRSA nasal surveillance swab (PCR-based or culture-based)
• Wound culture yielding methicillin-resistant Staphylococcus aureus without clinical signs of active wound infection
• Blood culture screen positive for MRSA in a patient who remains asymptomatic
• Any culture or molecular diagnostic result documented as “MRSA screen positive” by the ordering provider

Note: CPT 87641 (nucleic acid detection, MRSA, amplified probe technique) and 87081 (culture, presumptive, pathogenic organisms, screening) are the most common testing codes that generate supporting results for Z22.322.

What Is the Documentation Standard for Inpatient vs. Outpatient Settings?

How Does Z22.322 Affect Medical Billing and Claims?

Z22.322 carries specific billing behaviors that every revenue cycle team working in acute care or surgical settings should understand:

• Secondary diagnosis only — payers will reject Z22.322 as a principal diagnosis; it must follow the primary reason for the encounter
• Infection-control resource use — when Z22.322 appears on an inpatient claim, it can support medical necessity for contact/droplet precaution-related charges and isolation supplies
• DRG assignment — Z22.322 is grouped to MS-DRG 951 when it drives the DRG; as a secondary code paired with a surgical or medical principal diagnosis, it may trigger MCC/CC consideration depending on payer-specific DRG logic
• Pre-operative screening context — Z22.322 is frequently billed during pre-surgical workups; payers generally do not require prior authorization for the colonization code itself, but associated decolonization treatment may

What CPT Codes Are Commonly Billed With Z22.322?

Are There Coverage or Prior Authorization Restrictions?

• Medicare does not have an LCD specific to Z22.322 as a standalone code; coverage is driven by the primary diagnosis and medical necessity of the associated services
• Decolonization protocols (e.g., mupirocin nasal ointment, chlorhexidine body wash) may require separate medical necessity documentation
• Some Medicaid managed care plans restrict certain infection-control screening reimbursement to pre-operative contexts — verify payer-specific policy before billing
• Z22.322 is generally not subject to prior authorization as a diagnosis code; the associated procedures (CPT 87641, 87081) may require authorization under certain plans

What Coding Errors Should You Avoid With Z22.322?

Z22.322 generates a predictable set of mistakes that surface regularly in coding audit preparation and claim denial reviews:

1. Using Z22.322 as a principal diagnosis — the code cannot lead a claim; it will trigger an MCE edit and likely a claim rejection
2. Coding from the lab report without provider acknowledgment — a positive MRSA swab in the chart does not authorize Z22.322 unless the provider documents the carrier state; query if absent
3. Confusing Z22.322 with Z86.14 — Z86.14 is for resolved history only; Z22.322 requires current or suspected active colonization
4. Appending Z16.11 (resistance to penicillin) alongside Z22.322 — this pairing is incorrect per coding guidelines; the resistance is already implicit in the MRSA designation
5. Failing to assign both the colonization and infection codes when both are present — when a patient has confirmed MRSA colonization and an active MRSA infection during the same inpatient stay, guidelines explicitly support dual coding
6. Using Z22.322 for MSSA colonization — if sensitivity testing shows the organism is methicillin-susceptible, Z22.321 is required

What Do Auditors Look for When Reviewing Claims With Z22.322?

Auditors commonly flag the following patterns during claims review:

• Z22.322 appearing as the first-listed diagnosis on any claim type
• No corresponding lab result or provider notation in the chart to support the colonization finding
• Z22.322 billed on a claim where the same encounter also contains active MRSA infection codes without dual-coding justification
• Repeated use of Z22.322 across encounters with no updated clinical documentation confirming ongoing carrier status

How Does Z22.322 Relate to Other ICD-10 Codes?

Z22.322 sits within a family of MRSA-related codes that coders must be able to navigate fluently. Selecting the wrong sibling code — particularly using Z22.322 when an active infection code applies — is one of the most frequently cited MRSA coding errors in revenue cycle compliance audits.

What Is the Correct Code Sequencing When Z22.322 Appears With Other Diagnoses?

1. Principal diagnosis first — the condition chiefly responsible for the encounter (e.g., elective hip replacement, wound care, infectious disease consult)
2. Active MRSA infection code second — if applicable (e.g., A41.02 for MRSA sepsis)
3. Z22.322 third — as a secondary code documenting colonization status
4. Other comorbidities — sequenced per standard ICD-10-CM guidelines

When the sole reason for the encounter is management of known MRSA colonization (e.g., infectious disease follow-up visit, pre-op decolonization counseling), the primary condition driving that visit — such as the surgical condition prompting the pre-op workup — should lead.

Real-World Coding Scenario — How Z22.322 Is Applied in Practice

Scenario: A 68-year-old Medicare patient is admitted for elective left total knee replacement. On admission, hospital protocol triggers a nasal MRSA surveillance swab. The result returns positive. The attending orthopedic surgeon documents in the H&P: “Pre-operative MRSA nasal swab positive — patient is an MRSA carrier. Infectious disease consulted. Decolonization protocol initiated.” The patient has no wound infection, no fever, no elevated WBC, and no clinical signs of active MRSA disease. Surgery proceeds as planned.

Correct Code Application

• M17.12 — Primary osteoarthritis, left knee (principal diagnosis — reason for admission)
• Z22.322 — Carrier of MRSA (secondary; colonization documented by surgeon)
• Z96.651 — Presence of right artificial knee joint (if applicable from prior history)

Common Mistake in This Scenario

• Assigning B95.62 (MRSA as the cause of diseases classified elsewhere) alongside the knee replacement — this is incorrect because B95.62 is an additional code used when MRSA is causing an active infection, not for carrier status
• Omitting Z22.322 entirely because the patient had no active infection — the colonization is a documented condition affecting the patient’s health management (infection control precautions, decolonization) and should be captured

Frequently Asked Questions About ICD-10 Code Z22.322

Is ICD-10 Code Z22.322 Still Valid for Use in 2026?

Z22.322 remains a valid, billable ICD-10-CM diagnosis code for fiscal year 2026, effective October 1, 2025, with no changes to its description or validity status. Coders should verify annually against the CMS ICD-10-CM Official Tabular List release to confirm no structural updates have been applied.

What Is the Difference Between Z22.322 and Z22.321?

Z22.322 applies when the Staphylococcus aureus organism is methicillin-resistant (MRSA), while Z22.321 is used when the strain is methicillin-susceptible (MSSA). The distinction is determined by antimicrobial susceptibility testing results and must be reflected in the provider’s documentation — coders should not assign Z22.322 based on a positive staph culture alone without confirmation of methicillin resistance.

Can Z22.322 and an Active MRSA Infection Code Be Assigned Together?

Yes. Per ICD-10-CM Official Coding Guidelines Section I.C.1.e.1.d, when a patient has both documented MRSA colonization and an active MRSA infection during the same inpatient admission, both Z22.322 and the appropriate MRSA infection code may be assigned. The infection code sequences first as the more clinically significant finding.

When Should Z86.14 Be Used Instead of Z22.322?

Z86.14 (personal history of MRSA) should be used when the patient had a prior MRSA infection or colonization that has since resolved, with no current documentation of ongoing carriage. Z22.322 requires active or suspected current colonization; if the provider describes MRSA only in the past tense without confirming ongoing carrier status, Z86.14 is the correct choice.

Can a Coder Assign Z22.322 Based on a Lab Result Alone?

No. A positive MRSA culture or PCR result does not independently authorize assignment of Z22.322. The ICD-10-CM guidelines require that the provider document the carrier state in the clinical record. If only the lab report reflects the positive finding without provider acknowledgment, the coder must submit a provider query before assigning the code.

Is Z22.322 Acceptable as a Principal Diagnosis?

Z22.322 is not acceptable as a principal diagnosis. The Medicare Code Editor (MCE) flags this code as unacceptable in the first-listed position, and claims submitted with Z22.322 as the principal diagnosis will be rejected. It must always be sequenced as an additional code following the primary reason for the encounter.

Key Takeaways

• Z22.322 documents MRSA carrier or colonization status — not active infection; it reflects the organism’s presence without current clinical disease
• Provider documentation of colonization is required — positive lab results alone do not authorize this code; a provider query may be necessary
• Z22.322 is never the principal diagnosis and will trigger MCE edits if placed first on a claim
• Dual coding is correct when a patient has simultaneous colonization and active MRSA infection during the same inpatient stay — the infection code leads
• Distinguish carefully between Z22.322 (current MRSA colonization), Z22.321 (current MSSA colonization), and Z86.14 (historical MRSA only)
• Do not add Z16.11 or B95.62 alongside Z22.322 — these codes belong to active MRSA infection scenarios, not carrier status
• Review the ICD-10-CM Official Coding Guidelines Section I.C.1.e annually; this guideline section governs all MRSA and MSSA coding rules and is updated by CMS each fiscal year

For complete guideline text, refer to the CMS ICD-10-CM Official Guidelines for Coding and Reporting and the CDC MRSA surveillance resources for clinical context supporting accurate diagnosis documentation.