Question 1

What is ICD-10 code Z22.359?

Accepted Answer

Z22.359 is the ICD-10-CM diagnosis code for Carrier of Enterobacterales, unspecified. A person who carries Enterobacterales bacteria without being sick, but the specific type or resistance status is not specified or unknown. Z22.359 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. Z22.359 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Question 2

Is Z22.359 an HCC code?

Accepted Answer

No. Z22.359 is a billable ICD-10-CM code but does not map to any payment HCC category under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can still be reported on Medicare Advantage encounter data submissions, but it does not contribute to the beneficiary's Risk Adjustment Factor (RAF) score and therefore does not affect the risk-adjusted capitation payment to the plan. V28 reached 100% phase-in for payment year 2026.

Question 3

Is Z22.359 billable?

Accepted Answer

Yes. Z22.359 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. Z22.359 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Question 4

What is the V28 vs V24 difference for Z22.359?

Accepted Answer

Z22.359 does not map to a payment HCC under either the CMS-HCC V28 risk adjustment model or the older V24 model. V28 reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition. Because neither model rewards Z22.359 with a risk adjustment factor, it contributes zero to a Medicare Advantage beneficiary's RAF score in either version. Coders should check whether provider documentation supports a more specific child code that does map to a payment HCC.

Question 5

What should coders know when reporting Z22.359?

Accepted Answer

Use this code only when the Enterobacterales organism and its resistance pattern have not been determined Obtain and document culture results and susceptibility testing to assign a more specific code

Z22.359

Is Z22.359 an HCC code?

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Open Z22.359 in the Interactive Encoder