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Anti-Citrullinated Protein Antibody (ACPA) – Serum

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

This test measures antibodies against citrullinated proteins, which may help identify rheumatoid arthritis or other autoimmune conditions.

Quick summary

["ACPA testing supports early diagnosis of rheumatoid arthritis or related autoimmune diseases."]

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

Key facts at a glance

LOINC
17724-6
Short code
T palldm Ab Ser IF-aCnc
Synonyms
T palldm Ab Ser IF-aCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
if
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 your immune system produces in response to citrullinated proteins—commonly found in joints and blood vessels. These antibodies are strongly linked to rheumatoid arthritis (RA) and other inflammatory conditions like spondyloarthritis.

Why Might You Need This Test?

Your doctor may order this test if you have symptoms like joint pain, swelling, or stiffness—especially if they suspect an autoimmune condition. It can also help confirm a diagnosis or monitor disease activity in people already diagnosed with RA or similar disorders.

Sample Collection and Preparation

A blood sample is drawn from a vein in your arm. The serum portion (liquid after blood clotting) is used for testing. This process is quick and typically done in a doctor’s office or lab.

What to Expect Before or After Testing

No special preparation is needed, but avoid strenuous activity 24 hours before testing. Results may take a few days to weeks, depending on lab processing times.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Elevated ACPA levels strongly suggest rheumatoid arthritis or other citrullinemia-related autoimmune diseases. While not definitive alone, they improve diagnostic accuracy alongside other tests (e.g., rheumatoid factor). Monitoring ACPA over time can track disease progression or treatment response.

Short name

ACPA Antibody

Frequently asked questions

What does a positive ACPA test mean?
A positive result indicates your immune system is producing these antibodies, which may signal an increased risk of rheumatoid arthritis or another autoimmune condition. However, not everyone with positive ACPA develops RA, so further evaluation is needed.
Can lifestyle changes affect ACPA levels?
While lifestyle factors like diet or exercise may influence inflammation, they do not directly alter ACPA antibody levels. Your doctor will focus on symptoms and other diagnostic criteria for diagnosis.
Is this test covered by insurance?
Coverage depends on your insurance plan and clinical indication. Check with your provider to confirm if this test is approved for your specific situation.
  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