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Anti-Citrullinated Protein Antibody (ACPA) – Serum

Published: August 9, 2026Updated: August 16, 2026

This test measures antibodies that target citrullinated proteins, commonly used to help diagnose rheumatoid arthritis.

Quick summary

["ACPA helps identify rheumatoid arthritis risk by detecting specific immune responses in your blood."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
105081-4
Short code
Rheumatoid fact Spec-aCnc
Synonyms
Rheumatoid fact Spec-aCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
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

What Is This Test Measuring?

ACPA antibodies are proteins produced by your immune system when it mistakenly attacks healthy tissues, particularly in people with rheumatoid arthritis. This test detects these antibodies in your serum to assess inflammation and disease activity.

Why Might This Test Be Ordered?

Doctors may order this test if you have symptoms like joint pain, swelling, or stiffness—especially if other tests (like rheumatoid factor) are inconclusive. It can also help monitor disease progression or response to treatment.

How Is the Test Performed?

A blood sample is drawn from a vein, typically in your arm. The serum portion is then analyzed using an immunoassay method to measure ACPA levels.

What Does a Positive Result Mean?

A positive result suggests a higher likelihood of rheumatoid arthritis or other autoimmune conditions affecting joints. However, it’s not definitive on its own—your doctor will consider symptoms, other test results, and clinical findings.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

ACPA Antibody

Frequently asked questions

What does an elevated ACPA level indicate?
An elevated ACPA level increases the likelihood of rheumatoid arthritis or related autoimmune conditions, but it doesn’t confirm a diagnosis alone. Your doctor will use this result alongside other factors to guide treatment.
How long does it take to get results?
Results are typically available within 1–3 business days, depending on lab processing times.
Can lifestyle changes affect ACPA levels?
ACPA levels are not directly influenced by lifestyle changes like diet or exercise, but managing symptoms (e.g., through physical therapy or medications) may help slow disease progression.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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