ICD-10 Code M05.A: Abnormal rheumatoid factor and anti-citrullinated protein antibody with rheumatoid arthritis
M05.A is a billable ICD-10 diagnosis code used to classify Abnormal rheumatoid factor and anti-citrullinated protein antibody with rheumatoid arthritis in medical records and claims. You may see this code in hospital records, discharge summaries, insurance claims, encounter documentation, referrals, or other healthcare billing and coding records. ICD-10 codes are diagnosis classification codes used in healthcare records, reporting, coding workflows, and billing support. This code sits within the broader ICD-10 area for Diseases of the musculoskeletal system and connective tissue (M00-M99).
What is this code?
ICD-10 codes are diagnosis classification codes used in healthcare records, reporting, coding workflows, and billing support. This code sits within the broader ICD-10 area for Diseases of the musculoskeletal system and connective tissue (M00-M99).
When is it used?
- May be used when a clinician documents abnormal rheumatoid factor and anti-citrullinated protein antibody with rheumatoid arthritis in a patient's medical record.
- May appear in hospital records, claims, referrals, and clinical documentation.
- This code can be used as a clinically usable diagnosis entry in standardized coding workflows.
What it does not mean
- A code alone does not explain severity, treatment plan, or outcome.
- A medical code should not be treated as a substitute for a doctor's diagnosis or advice.
Code hierarchy
Official coding notes
- rheumatoid arthritis with rheumatoid factor by site, if known (M05.00 to M05.8A)
- rheumatoid arthritis with rheumatoid factor by site, if known (M05.00 to M05.8A)
Where you may see this code
You may see this code in hospital records, discharge summaries, insurance claims, encounter documentation, referrals, or other healthcare billing and coding records.
Related specialists
Related codes
Sibling codes
Coverage-related procedures and services
Coding guidelines
Common synonyms
Frequently asked questions
About this content
This page is prepared by HealthAssure's clinical team using official coding standards from ICD-10. AI tools assist with drafting explanations, which are then reviewed and verified by healthcare professionals for accuracy. This content is for informational purposes and does not replace professional medical advice. Meet our team.