A01.04 ICD-10-CM Code: Typhoid arthritis
HCC Buddy Code Card
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FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Intestinal infectious diseases (A00-A09)
A01.04
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceTyphoid arthritis
Typhoid arthritis is joint inflammation that develops as a complication of typhoid fever, a serious bacterial infection caused by Salmonella typhi. This condition causes pain, swelling, and stiffness in the affected joints during or after typhoid infection.
Buddy Insight
Typhoid arthritis is a rare but clinically significant infectious arthritis caused by Salmonella typhi dissemination to joint spaces.
CMS-HCC V28
MappedHCC 92
RAF 0.479
CMS-HCC V24
MappedHCC 39
RAF 0.401
ACA/HHS
MappedHCC 55
Varies by metal level
ESRD/PACE
MappedHCC 39
RAF 0.092
RXHCC
N/A—
Not mapped
Code Book Path
Inclusion Terms
Official- Infection due to Salmonella typhi
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for A01.04 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for A01.04 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for A01.04 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for A01.04 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for A01.04 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for A01.04 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
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 A01.04 an HCC code?
Yes. A01.04 (Typhoid arthritis) maps to Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis under the CMS-HCC V28 risk adjustment model (and Bone/Joint/Muscle Infections/Necrosis under V24), with a community non-dual aged RAF of 0.479. It is billable for payment year 2026.
Coder answer: A01.04 is billable and maps to V28 HCC 92, Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- A01.04
- Description
- Typhoid arthritis
- HCC (V28)
- HCC 92 — Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis
- RAF
- 0.479
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
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 A01.04 in the Code Book — tabular path, V28 RAF, and MEAT checklist →
MEAT Criteria for A01.04
For A01.04 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 A01.04 during that encounter, not just copy-forwarded from a problem list.
Coder workflow notes
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What This Code Means
A01.04 is the ICD-10-CM diagnosis code for typhoid arthritis. Typhoid arthritis is joint inflammation that develops as a complication of typhoid fever, a serious bacterial infection caused by Salmonella typhi. This condition causes pain, swelling, and stiffness in the affected joints during or after typhoid infection. A01.04 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering intestinal infectious diseases (a00-a09).
Under the CMS-HCC V28 risk adjustment model, A01.04 maps to Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis (HCC 92) with a community, non-dual, aged base RAF weight of 0.479. Under the older CMS-HCC V24 model, A01.04 maps to Bone/Joint/Muscle Infections/Necrosis (HCC 39) with a community, non-dual, aged base RAF weight of 0.401. 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.
This code should only be used when arthritis is documented as a direct complication of typhoid fever; do not use if arthritis is unrelated to the typhoid infection. Because A01.04 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 A01.04 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This code should only be used when arthritis is documented as a direct complication of typhoid fever; do not use if arthritis is unrelated to the typhoid infection
- •Verify that the patient has confirmed typhoid fever diagnosis and that the arthritis manifestation is explicitly documented by the provider before assigning this code
Clinical Significance
Typhoid arthritis is a rare but clinically significant infectious arthritis caused by Salmonella typhi dissemination to joint spaces. It indicates systemic infection severity and can lead to joint destruction if not promptly treated with appropriate antibiotics and possible joint drainage.
Documentation Requirements
- ✓Documented Salmonella typhi infection with joint involvement
- ✓Specific joint(s) affected with clinical findings (swelling, erythema, limited range of motion)
- ✓Synovial fluid analysis results if performed (culture, cell count, crystal analysis to rule out gout)
- ✓Imaging of affected joint(s) showing effusion or destructive changes
- ✓Documentation of causal relationship between typhoid and the arthritis
Commonly Confused Codes
- •A02.23 (Salmonella arthritis): Use A02.23 for non-typhi Salmonella joint infections; A01.04 is specifically for S. typhi arthritis
- •M00.9 (Pyogenic arthritis, unspecified): Use A01.04 when the infectious arthritis is specifically attributed to typhoid fever
- •A01.00 (Typhoid fever, unspecified): Use A01.04 when arthritis is a documented complication, not the unspecified typhoid code