What is ICD-10 code J4A.9?

J4A.9 is the ICD-10-CM diagnosis code for Chronic lung allograft dysfunction, unspecified. A general category for long-term dysfunction of a transplanted lung when the specific type of dysfunction is not specified. It belongs to the ICD-10-CM chapter for diseases of the respiratory system (j00-j99). J4A.9 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. J4A.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.

Yes. J4A.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. J4A.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.

Which HCC does J4A.9 map to under V28?

J4A.9 maps to CMS-HCC V28 276 (Lung Transplant Status/Complications). The category number and label come from the CMS-HCC V28 model file for payment year 2026.

What does J4A.9 pay in RAF?

J4A.9 carries a community, non-dual, aged (CNA) RAF weight of 2.531 under CMS-HCC V28 for payment year 2026. The weight comes from the CMS V28 relative-factor file, not a hand-typed table.

What is the V28 vs V24 difference for J4A.9?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. For J4A.9, V28 maps to Lung Transplant Status/Complications at RAF 2.531 while V24 mapped to Major Organ Transplant or Replacement Status at RAF 0.832. Both models can still appear in legacy data and in payer-specific lookback periods.

What documentation supports J4A.9?

Use only when chronic lung allograft dysfunction is documented but the specific type is not identified Query provider for more specific diagnosis if possible (restrictive vs. obstructive pattern) Because J4A.9 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score. See the MEAT criteria checklist at /meat-criteria for what Monitor, Evaluate, Assess, or Treat looks like in a note. MEAT is generic documentation evidence, not a payer-specific rule.

2026 ICD-10-CM J4A.9: Chronic lung allograft

J4A.9 maps to CMS-HCC V28 276 (RAF 2.531). Documentation must support MEAT. MEAT criteria · RAF calculator · HCC Buddy coding tools

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Code lookupJ4A.9Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the respiratory system (J00-J99) / Chronic lower respiratory diseases (J40-J4A)

J4A.9

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

Chronic lung allograft dysfunction, unspecified

A general category for long-term dysfunction of a transplanted lung when the specific type of dysfunction is not specified.

Buddy Insight

Chronic lung allograft dysfunction, unspecified is used when a lung transplant recipient develops chronic decline in graft function but the specific phenotype (restrictive vs.

CMS-HCC V28

Mapped

HCC 276

Lung Transplant Status/Compli...

RAF 2.531

CMS-HCC V24

Mapped

HCC 186

Major Organ Transplant or Rep...

RAF 0.832

ACA/HHS

Mapped

HCC 158

HHS-HCC 158

Varies by metal level

ESRD/PACE

Mapped

HCC 186

Major Organ Transplant or Rep...

RAF 0.138

RXHCC

Mapped

HCC 396

Allograft Complications

Not separately weighted

Code Book Path

Official

J4AChronic lung allograft dysfunction

J4A.9Chronic lung allograft dysfunction, unspecified

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for J4A.9 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for J4A.9 in this effective period.

Related Child Codes

Official

J4A.0Restrictive allograft syndrome

J4A.8Other chronic lung allograft dysfunction

Includes

Official

ICD-10-CM does not list Includes notes for J4A.9 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for J4A.9 in this effective period.

Code First

Official

, if applicable:
heart-lung transplant rejection (T86.31)
lung transplant rejection (T86.810)
other complications of heart-lung transplant (T86.39)
other complications of lung transplant (T86.818)

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for J4A.9 in this effective period.

Code Also

Official

, if applicable, bronchiolitis obliterans syndrome (J44.81)

Buddy Documentation Tip

HCC Buddy guidance

Lung transplant history and date of transplantation

Documentation of chronic decline in lung function post-transplant

Pulmonary function testing showing persistent decline from baseline

Documentation that specific CLAD phenotype has not been determined

MEAT Support

HCC Buddy guidance

Lung transplant history and date of transplantation

Documentation of chronic decline in lung function post-transplant

Pulmonary function testing showing persistent decline from baseline

Documentation that specific CLAD phenotype has not been determined

Audit Caution

HCC Buddy guidance

Using unspecified CLAD when the specific phenotype is documented — always code to highest specificity

Not querying the transplant pulmonologist for CLAD phenotyping when possible

Confusing CLAD with acute rejection — these are different clinical entities

Forgetting to code lung transplant status (Z94.2) as an additional diagnosis

Common Mistakes

HCC Buddy guidance

J4A.0 — Restrictive allograft syndrome: preferred when restrictive pattern is documented

J4A.8 — Other chronic lung allograft dysfunction: preferred when a specific non-RAS/BOS type is identified

J44.81 — Bronchiolitis obliterans syndrome: preferred when obstructive pattern is documented

T86.810 — Lung transplant rejection: different concept — acute rejection vs. chronic dysfunction

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 J4A.9 an HCC code?

Yes. J4A.9 (Chronic lung allograft dysfunction, unspecified) maps to Lung Transplant Status/Complications under the CMS-HCC V28 risk adjustment model (and Major Organ Transplant or Replacement Status under V24), with a community non-dual aged RAF of 2.531. It is billable for payment year 2026.

Coder answer: J4A.9 is billable and maps to V28 HCC 276, Lung Transplant Status/Complications. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code: J4A.9
Description: Chronic lung allograft dysfunction, unspecified
HCC (V28): HCC 276 — Lung Transplant Status/Complications
RAF: 2.531
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 276, Lung Transplant Status/Complications

2.531

V24HCC 186, Major Organ Transplant or Replacement Status

0.832

ESRDHCC 186, Major Organ Transplant or Replacement Status

0.138

RxHCCHCC 396, Allograft Complications

Not separately weighted

Each model's RAF is its CMS base weight for that model's standard population, so 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 segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

Work J4A.9 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for J4A.9

For J4A.9 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

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

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed J4A.9 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

J4A.9 is the ICD-10-CM diagnosis code for chronic lung allograft dysfunction, unspecified. A general category for long-term dysfunction of a transplanted lung when the specific type of dysfunction is not specified. J4A.9 sits in the ICD-10-CM chapter for diseases of the respiratory system (j00-j99), within the section covering chronic lower respiratory diseases (j40-j4a).

Under the CMS-HCC V28 risk adjustment model, J4A.9 maps to Lung Transplant Status/Complications (HCC 276) with a community, non-dual, aged base RAF weight of 2.531. Under the older CMS-HCC V24 model, J4A.9 maps to Major Organ Transplant or Replacement Status (HCC 186) with a community, non-dual, aged base RAF weight of 0.832. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.

Use only when chronic lung allograft dysfunction is documented but the specific type is not identified. Because J4A.9 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. 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, RAF weights, and MEAT documentation criteria for J4A.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Use only when chronic lung allograft dysfunction is documented but the specific type is not identified
•Query provider for more specific diagnosis if possible (restrictive vs. obstructive pattern)

Clinical Significance

Chronic lung allograft dysfunction, unspecified is used when a lung transplant recipient develops chronic decline in graft function but the specific phenotype (restrictive vs. obstructive vs. mixed) has not been determined or documented. This code still carries significant risk adjustment weight, reflecting the severity of post-transplant complications.

Documentation Requirements

✓Lung transplant history and date of transplantation
✓Documentation of chronic decline in lung function post-transplant
✓Pulmonary function testing showing persistent decline from baseline
✓Documentation that specific CLAD phenotype has not been determined
✓Current immunosuppression and treatment adjustments
✓Clinical rationale for why the dysfunction type is unspecified

Commonly Confused Codes

•J4A.0: Restrictive allograft syndrome: preferred when restrictive pattern is documented
•J4A.8: Other chronic lung allograft dysfunction: preferred when a specific non-RAS/BOS type is identified
•J44.81: Bronchiolitis obliterans syndrome: preferred when obstructive pattern is documented
•T86.810: Lung transplant rejection: different concept: acute rejection vs. chronic dysfunction
•Z94.2: Lung transplant status: code additionally