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Quantitative Immunoassay for Anti-Citrullinated Protein Antibodies (ACPA) in Serum

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

This test measures the presence of antibodies that target citrullinated proteins, often linked to rheumatoid arthritis.

Quick summary

["ACPA antibodies may help diagnose or monitor rheumatoid arthritis."]

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

Key facts at a glance

LOINC
6354-5
Short code
C trach Ag Spec Ql IA
Synonyms
C trach Ag Spec Ql IA
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ia
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

The test detects ACPA, a type of antibody that attacks proteins modified by citrullination—a process involved in inflammation. Elevated levels may indicate an autoimmune response, particularly in rheumatoid arthritis.

Why It’s Done

Doctors may order this test to help diagnose rheumatoid arthritis, assess disease activity, or monitor treatment progress in patients with suspected autoimmune conditions.

How It’s Performed

A blood sample is drawn, and the serum is analyzed using an immunoassay method to quantify ACPA levels. Results are compared to reference ranges to determine significance.

What the Results Mean

Positive results suggest a higher likelihood of rheumatoid arthritis or other autoimmune diseases, but they are not definitive alone. Results should be interpreted alongside clinical findings and other tests.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

ACPA Antibody Test

Frequently asked questions

What symptoms might this test be done for?
This test is often used in patients with joint pain, swelling, stiffness, or other symptoms suggestive of rheumatoid arthritis. It may also be part of a broader evaluation for autoimmune disorders.
How soon will I get my results?
Results are typically available within 1–3 business days, depending on lab processing times. Your healthcare provider will discuss the findings with you.
Can I fast before this test?
No fasting is required for this blood test. However, follow any specific instructions your provider gives you before your appointment.
  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