Anti-Citrullinated Protein Antibody (ACPA) by Immunoassay (Serum/Plasma)
This test measures antibodies against citrullinated proteins, which are linked to rheumatoid arthritis. It helps diagnose or monitor the disease by detecting an immune response in your blood.
["ACPA antibodies may indicate early rheumatoid arthritis or help track disease activity."]
Key facts at a glance
- LOINC
- 94874-5
- Short code
- cCP IgG SerPl IA-aCnc
- Synonyms
- cCP IgG SerPl IA-aCnc
- Category
- coagulation
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- ia
- CPT
- 82784
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
Why This Test Matters for Your Health
Rheumatoid arthritis (RA) is an autoimmune condition where your immune system mistakenly attacks healthy joints. ACPA antibodies are a specific marker for RA, appearing in many patients before classic symptoms like joint pain or swelling develop. This test can help doctors confirm a diagnosis, assess disease severity, or guide treatment decisions.
How the Test Works
Your blood sample is tested using an immunoassay method to detect ACPA antibodies. The test identifies whether your immune system has produced these proteins, which are linked to inflammation and joint damage in RA.
What to Expect Before the Test
No special preparation is needed, but you may want to avoid aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs) for a few days before testing, as they can affect blood test results. Fasted or nonfasted blood draws are typically acceptable.
Common Reasons for This Test
Doctors may order this test if you have symptoms like joint pain, stiffness, or swelling—especially if these symptoms last more than a few weeks. It’s also used in patients with unexplained joint inflammation, family history of RA, or other autoimmune conditions.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
High ACPA levels strongly suggest rheumatoid arthritis, often appearing years before symptoms or other diagnostic tests like X-rays. While not all RA patients test positive, ACPA is highly specific for the disease. It can also help monitor disease progression or response to treatment by tracking antibody levels over time.
Short name
ACPA Antibody
Frequently asked questions
What does a positive ACPA test mean?
Can ACPA levels change over time?
Is this test covered by insurance?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy