A43.9 ICD-10-CM Code: Nocardiosis, unspecified
HCC Buddy Code Card
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FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Other bacterial diseases (A30-A49)
A43.9
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceNocardiosis, unspecified
Nocardiosis is a rare bacterial infection caused by Nocardia organisms that can affect the lungs, skin, or brain, particularly in people with weakened immune systems. This code is used when the specific type or location of the nocardiosis infection is not documented.
CMS-HCC V28
00
RAF 0
CMS-HCC V24
00
RAF 0
ACA/HHS
00
RAF 0
ESRD/PACE
00
RAF 0
RXHCC
00
RAF 0
Code Trumping
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Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for A43.9 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for A43.9 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for A43.9 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for A43.9 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for A43.9 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for A43.9 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for A43.9 in this effective period.
Buddy Documentation Tip
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is A43.9 an HCC code?
No. A43.9 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
This code does not map to an HCC category in any model (V28, V24, ESRD, RxHCC).
What This Code Means
A43.9 is the ICD-10-CM diagnosis code for nocardiosis, unspecified. Nocardiosis is a rare bacterial infection caused by Nocardia organisms that can affect the lungs, skin, or brain, particularly in people with weakened immune systems. This code is used when the specific type or location of the nocardiosis infection is not documented. A43.9 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering other bacterial diseases (a30-a49).
A43.9 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.
Query the provider if the site of infection (pulmonary, cutaneous, or CNS) is documented, as more specific codes (A43.0, A43.1, A43.8) provide better clinical detail and may affect treatment decisions.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for A43.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Query the provider if the site of infection (pulmonary, cutaneous, or CNS) is documented, as more specific codes (A43.0, A43.1, A43.8) provide better clinical detail and may affect treatment decisions
- •This unspecified code should only be used when the documentation truly does not specify the type or location of nocardiosis; avoid using it as a default when more specific information is available in the medical record