A31.0 maps to CMS-HCC V28 6. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC coding software

ICD-10-CM Code View

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Code lookupA31.0

Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Other bacterial diseases (A30-A49)

A31.0

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Pulmonary mycobacterial infection

This is a bacterial lung infection caused by mycobacteria (a type of bacteria), which is different from the more common tuberculosis. It affects the lungs and respiratory system, causing symptoms like cough and breathing difficulties.

Buddy Insight

Pulmonary mycobacterial infection (nontuberculous mycobacteria, or NTM) is a chronic progressive lung disease most commonly caused by Mycobacterium avium complex (MAC) or M.

Overview Risk Models Code Book Documentation Audit Notes Edition comparison

CMS-HCC V28

Mapped

HCC 6

Opportunistic Infections

Coefficient HCC 6: 0.381 (Community Non-Dual Aged (CNA))

CMS-HCC V24

Historical

Not used for standard CY2026 Medicare Advantage payment. Select a historical period to review V24.

Not used for CY2026 payment

ACA/HHS

Mapped

HCC 006

HHS-HCC 006 adult, RAF varies...

Code-level coefficient reference

ESRD/PACE

Mapped

HCC 6

Opportunistic Infections

Code-level coefficient reference

RXHCC

Mapped

HCC 5

Opportunistic Infections

Code-level coefficient reference

Code Book Path

Official

A31Infection due to other mycobacteria A31.0Pulmonary mycobacterial infection

Inclusion Terms

Official

Infection due to Mycobacterium avium
Infection due to Mycobacterium intracellulare [Battey bacillus]
Infection due to Mycobacterium kansasii

Excludes 2

Official

carrier or suspected carrier of infectious disease (Z22.-)Inherited from A00-B99, A31
infectious and parasitic diseases complicating pregnancy, childbirth and the puerperium (O98.-)Inherited from A00-B99, A31
infectious and parasitic diseases specific to the perinatal period (P35-P39)Inherited from A00-B99, A31
influenza and other acute respiratory infections (J00-J22)Inherited from A00-B99, A31
leprosy (A30.-)Inherited from A00-B99, A31
tuberculosis (A15-A19)Inherited from A00-B99, A31

Related Codes

Official

A31.1Cutaneous mycobacterial infection A31.2Disseminated mycobacterium avium-intracellulare complex (DMAC)A31.8Other mycobacterial infections A31.9Mycobacterial infection, unspecified

Includes

Official

diseases generally recognized as communicable or transmissibleInherited from A00-B99

Excludes 1

Official

certain localized infections - see body system-related chaptersInherited from A00-B99

Code First

Official

No Code First sequencing instructions are included in this display for A31.0. Check the code and parent instructions in the Code Book.

Use Additional

Official

code to identify resistance to antimicrobial drugs (Z16.-)Inherited from A00-B99

Code Also

Official

No Code Also instructions are included in this display for A31.0. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance

Sputum cultures identifying specific NTM species (at least 2 positive sputum cultures, or 1 positive bronchial wash/BAL)

CT chest showing nodular bronchiectatic or cavitary disease pattern

Clinical symptoms consistent with pulmonary NTM (chronic cough, fatigue, weight loss)

Exclusion of other diagnoses, particularly pulmonary tuberculosis

MEAT Support

HCC Buddy guidance

Sputum cultures identifying specific NTM species (at least 2 positive sputum cultures, or 1 positive bronchial wash/BAL)

CT chest showing nodular bronchiectatic or cavitary disease pattern

Clinical symptoms consistent with pulmonary NTM (chronic cough, fatigue, weight loss)

Exclusion of other diagnoses, particularly pulmonary tuberculosis

Audit Caution

HCC Buddy guidance

Do not confuse NTM pulmonary disease with tuberculosis — they require different treatment and have different public health implications

Colonization vs. active disease: A31.0 should only be coded when the ATS/IDSA diagnostic criteria for disease (not just colonization) are met

If the specific mycobacterial species is documented, this code still applies for pulmonary NTM — there is no further specificity available in ICD-10

Common Mistakes

HCC Buddy guidance

A15.0 (Tuberculosis of lung) — Tuberculosis is caused by M. tuberculosis; A31.0 is specifically for nontuberculous mycobacteria

A31.2 (Disseminated mycobacterium avium-intracellulare complex) — Use A31.2 when MAC infection is disseminated beyond the lungs; A31.0 is for pulmonary-only disease

A31.9 (Mycobacterial infection, unspecified) — Use A31.0 when pulmonary involvement is documented, not the unspecified code

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is A31.0 an HCC code?

Yes. A31.0 (Pulmonary mycobacterial infection) maps to HCC 6, Opportunistic Infections under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.381. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.

Coder answer: A31.0 is billable and maps to V28 HCC 6, Opportunistic Infections. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: A31.0
Description: Pulmonary mycobacterial infection
HCC (V28): HCC 6 — Opportunistic Infections
RAF reference coefficient: 0.381
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 6, Opportunistic Infections

0.381

ESRDHCC 6, Opportunistic Infections

Not separately weighted

RxHCCHCC 5, Opportunistic Infections

Not separately weighted

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work A31.0 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for A31.0

For A31.0, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
EEvaluate: test results, medication response, or physical findings reviewed by the provider
AAssess: explicit mention in the assessment or plan with acknowledgment of status
TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Coder workflow notes

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What This Code Means

A31.0 is the ICD-10-CM diagnosis code for pulmonary mycobacterial infection. This is a bacterial lung infection caused by mycobacteria (a type of bacteria), which is different from the more common tuberculosis. It affects the lungs and respiratory system, causing symptoms like cough and breathing difficulties. A31.0 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering other bacterial diseases (a30-a49).

Under the CMS-HCC V28 risk adjustment model, A31.0 maps to Opportunistic Infections (HCC 6) with a source-labeled community, non-dual, aged reference coefficient of 0.381. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.

Verify the specific type of mycobacterial infection (such as MAC - Mycobacterium avium complex) as this may require additional specificity codes. For A31.0, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for A31.0 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Verify the specific type of mycobacterial infection (such as MAC - Mycobacterium avium complex) as this may require additional specificity codes
•Confirm whether this is a primary infection or a secondary/opportunistic infection, particularly in immunocompromised patients, as this may affect coding accuracy

Clinical Significance

Pulmonary mycobacterial infection (nontuberculous mycobacteria, or NTM) is a chronic progressive lung disease most commonly caused by Mycobacterium avium complex (MAC) or M. abscessus. It predominantly affects elderly women with bronchiectasis (Lady Windermere syndrome) and immunocompromised patients, requiring prolonged multi-drug treatment regimens often lasting 12-18 months.

Documentation Requirements

✓Sputum cultures identifying specific NTM species (at least 2 positive sputum cultures, or 1 positive bronchial wash/BAL)
✓CT chest showing nodular bronchiectatic or cavitary disease pattern
✓Clinical symptoms consistent with pulmonary NTM (chronic cough, fatigue, weight loss)
✓Exclusion of other diagnoses, particularly pulmonary tuberculosis
✓ATS/IDSA diagnostic criteria met: clinical, radiographic, and microbiologic criteria all fulfilled

Commonly Confused Codes

•A15.0 (Tuberculosis of lung): Tuberculosis is caused by M. tuberculosis; A31.0 is specifically for nontuberculous mycobacteria
•A31.2 (Disseminated mycobacterium avium-intracellulare complex): Use A31.2 when MAC infection is disseminated beyond the lungs; A31.0 is for pulmonary-only disease
•A31.9 (Mycobacterial infection, unspecified): Use A31.0 when pulmonary involvement is documented, not the unspecified code