M05.A Abnormal rheumatoid factor and anti-citrullinated protein antibody with rheumatoid arthritis

Billable ICD-10-CM code, FY2026.

Code first

• rheumatoid arthritis with rheumatoid factor by site, if known (M05.00 to M05.8A)

Applies from M05 Rheumatoid arthritis with rheumatoid factor

Excludes1 (never code together)

• rheumatic fever (I00)
• juvenile rheumatoid arthritis (M08.-)
• rheumatoid arthritis of spine (M45.-)

Risk adjustment (HCC)

• CMS-HCC V28: HCC 93 — Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders
• CMS-HCC V22: HCC 40 — Rheumatoid Arthritis and Inflammatory Connective Tissue Disease
• RxHCC V08: HCC 83 — Rheumatoid Arthritis and Other Inflammatory Polyarthropathy
• ESRD V24: HCC 40

MS-DRG index

Defines the logic of DRG(s) 545-547 in MDC 08.

Code annotations containing back-references to M05.A

Back-references to M05

• Code Also: I27.21 Secondary pulmonary arterial hypertension ("rheumatoid arthritis (M05.-)")
• Type 1 Excludes: R76.81 Abnormal rheumatoid factor and anti-citrullinated protein antibody without rheumatoid arthritis ("rheumatoid arthritis with rheumatoid factor (M05.-)")

Diagnosis Index entries for M05.A

• Abnormal, abnormality, abnormalities › rheumatoid factor and anti-citrullinated protein antibody › with rheumatoid arthritis

Nearby codes

• M05.872 Other rheumatoid arthritis with rheumatoid factor of left ankle and foot
• M05.879 Other rheumatoid arthritis with rheumatoid factor of unspecified ankle and foot
• M05.89 Other rheumatoid arthritis with rheumatoid factor of multiple sites
• M05.8A Other rheumatoid arthritis with rheumatoid factor of other specified site
• M05.9 Rheumatoid arthritis with rheumatoid factor, unspecified
• M05.A Abnormal rheumatoid factor and anti-citrullinated protein antibody with rheumatoid arthritis (this code)