Skip to content

Anti-Citrullinated Protein Antibody (ACPA) in Serum/Plasma

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

This test measures antibodies that target citrullinated proteins, often linked to rheumatoid arthritis. It helps diagnose or monitor the disease by detecting immune system activity against these proteins.

Quick summary

["ACPA helps identify rheumatoid arthritis earlier and track disease progression or treatment response."]

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

Key facts at a glance

LOINC
17725-3
Short code
T palldm Ab Ser LA-aCnc
Synonyms
T palldm Ab Ser LA-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
la
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 Is This Test Done?

Your doctor may order this test if you have symptoms like joint pain, swelling, or stiffness—especially if they suspect rheumatoid arthritis. It can also be used to confirm a diagnosis or assess disease activity in people already suspected of having the condition.

What Does a Positive Result Mean?

A positive result indicates the presence of ACPA antibodies, which are strongly associated with rheumatoid arthritis. However, not everyone with rheumatoid arthritis will test positive, so results are interpreted alongside other clinical findings.

How Is the Test Performed?

A blood sample is drawn from a vein in your arm. The serum or plasma is then tested for ACPA antibodies using an immunoassay method, which detects the presence of these antibodies in your blood.

What Are Common Results and Next Steps?

If your results are positive, your doctor may recommend further testing (like rheumatoid factor) or monitoring to confirm or rule out rheumatoid arthritis. If negative, other causes of joint symptoms may be explored.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

ACPA (Serum/Plasma)

Frequently asked questions

What does an ACPA test measure?
It measures the presence of antibodies that target citrullinated proteins in your blood, often linked to rheumatoid arthritis.
How soon after symptoms do ACPA levels usually appear?
ACPA antibodies can appear years before rheumatoid arthritis symptoms develop, sometimes even decades earlier.
Can lifestyle changes affect ACPA test results?
No, ACPA test results are not influenced by lifestyle factors like diet or exercise. They reflect your immune system’s response to specific proteins in your body.
  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