Question 1

What is ICD-10 code A03.9?

Accepted Answer

A03.9 is the ICD-10-CM diagnosis code for Shigellosis, unspecified. Shigellosis is a bacterial infection of the intestines caused by Shigella bacteria, resulting in diarrhea, abdominal cramps, and fever. This code is used when the specific type of Shigella bacteria has not been identified or documented. A03.9 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. A03.9 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 A03.9 an HCC code?

Accepted Answer

No. A03.9 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 A03.9 billable?

Accepted Answer

Yes. A03.9 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. A03.9 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 A03.9?

Accepted Answer

A03.9 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 A03.9 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 A03.9?

Accepted Answer

Use this unspecified code only when the medical record does not specify which Shigella species (A03.0-A03.8) caused the infection; always attempt to obtain more specific documentation from the provider Shigellosis is typically a reportable disease to public health authorities, so ensure proper documentation and reporting requirements are met in addition to coding

A03.9

Is A03.9 an HCC code?

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Open A03.9 in the Interactive Encoder