ICD-10 M05.A
Billable / Specific HCC v28: 40Abnormal rheumatoid factor and anti-citrullinated protein antibody with rheumatoid arthritis
About ICD-10-CM M05.A
ICD-10-CM code M05.A represents Abnormal rheumatoid factor and anti-citrullinated protein antibody with rheumatoid arthritis. This is a billable/specific code in the Musculoskeletal and Connective Tissue chapter (block M05). The 2026 edition of ICD-10-CM M05.A became effective on October 1, 2025.
Coding Tips for M05.A
Specialist guidance from the PayerReady Medical Coding Team. Specificity warnings, HCC capture rules, sequencing notes.
M05.A is a CMS-HCC v28 risk-adjustment code (category 40). To count for the patient Risk Adjustment Factor (RAF), document the diagnosis with MEAT language each calendar year: Monitored, Evaluated, Assessed, Treated. A diagnosis on the problem list alone does not satisfy CMS RADV audit standards. Include the diagnosis in the assessment with current status and current treatment plan.
Coding Notes
Code First
- rheumatoid arthritis with rheumatoid factor by site, if known (M05.00 to M05.8A)
Medicare Advantage HCC Impact
Capture this diagnosis annually for accurate risk adjustment. Missed HCC captures are the #1 revenue leak in Medicare Advantage risk programs.
Medicare LCD Coverage for M05.A
Local Coverage Determinations (LCDs) from CMS MACs that list M05.A as a covered diagnosis.
Showing top 10. Click a CPT for full coverage scope.
Commercial Payer Coverage
Coverage policies from major commercial payers referencing M05.A.
4 Cigna
2 Medicare
CPT Codes Commonly Billed with M05.A
Procedures frequently paired with this diagnosis based on PayerReady's Dx↔Px linkage data.
We don't have CPT pairings indexed for this specific code yet. Use the CPT search above to find common procedures, or check your payer's published medical policy for code-specific guidance.
Codes Adjacent To M05.A
Other codes in section M05-M14 (Inflammatory polyarthropathies).
ICD-10 M05.A, Billing FAQ
Is ICD-10 code M05.A billable? +
Yes, M05.A is a billable ICD-10-CM code that can appear as a primary or secondary diagnosis on claims.
Does M05.A affect Medicare Advantage HCC risk adjustment? +
Yes. M05.A maps to CMS-HCC v28 category 40. Capture this diagnosis annually for accurate Medicare Advantage risk score.
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Reviewed by the PayerReady Medical Coding Team
Verified against the CMS 2026 code set on May 31, 2026.
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