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Anti-Citrullinated Protein Antibody (ACPA) by Immunoassay, Serum

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

This test measures antibodies that target proteins modified by citrulline, a process linked to rheumatoid arthritis. It helps assess your risk for or progression of inflammatory joint disease.

Quick summary

["ACPA testing may help diagnose or monitor rheumatoid arthritis by detecting specific immune responses."]

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

Key facts at a glance

LOINC
97558-1
Short code
AChR Bind IgG+IgM Ser IA-sCnc
Synonyms
AChR Bind IgG+IgM Ser IA-sCnc
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

What This Test Measures

ACPA antibodies are proteins produced by your immune system that attack citrullinated proteins—commonly found in joints and blood vessels. This test detects their presence in your serum, which can signal an autoimmune response tied to conditions like rheumatoid arthritis.

Why It’s 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’s also used to monitor disease activity in people already diagnosed with rheumatoid arthritis.

How It Works

A small blood sample is drawn, and the serum is tested using an immunoassay method to identify ACPA antibodies. This method detects the antibodies’ presence without measuring their exact concentration.

What to Expect

No special preparation is needed, but fasting isn’t required. Results may take 1–3 business days, depending on your lab. Follow-up with your healthcare provider to discuss results and next steps.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

ACPA (Serum)

Frequently asked questions

What does a positive ACPA test mean?
A positive result suggests an increased risk of rheumatoid arthritis or an active inflammatory process in your joints. It doesn’t confirm the diagnosis alone but supports further evaluation, such as joint imaging or additional blood tests.
Can ACPA test results change over time?
Yes, ACPA levels can fluctuate. They may rise or fall as your condition evolves, so results are often interpreted alongside clinical symptoms and other lab tests. Regular monitoring may be needed if you’re managing rheumatoid arthritis.
Does diet or lifestyle affect ACPA test results?
No, ACPA testing doesn’t depend on diet or lifestyle factors. However, your overall health and disease activity (e.g., joint inflammation) may indirectly influence how your body responds to the condition linked to these antibodies.
  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