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Serum or Plasma Anti-Citrullinated Protein Antibody (ACPA) by Immunoassay

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

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

Quick summary

["ACPA antibodies can signal inflammation linked to certain autoimmune diseases."]

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

Key facts at a glance

LOINC
11597-2
Short code
T palldm Ab Ser-aCnc
Synonyms
T palldm Ab Ser-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 This Test Measures

ACPA antibodies are proteins your immune system produces in response to citrullinated proteins—commonly found in joints and connective tissues. This test detects their presence in your blood, often used alongside other markers to assess rheumatoid arthritis risk or activity.

Why It’s Done

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 helps distinguish rheumatoid arthritis from other conditions or confirm disease progression.

Sample Collection

A blood sample is drawn from a vein, typically in your arm. The blood is processed into serum or plasma for testing. Avoid strenuous activity or certain medications (like NSAIDs) for 24 hours before testing, as they may affect results.

What to Expect

You’ll likely receive results within 1–3 business days. If positive, further evaluation (like physical exams, imaging, or other blood tests) may follow to guide treatment. Results alone don’t diagnose disease—they’re part of a broader assessment.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

ACPA Antibody Test

Frequently asked questions

How does ACPA testing differ from rheumatoid factor testing?
ACPA tests focus on antibodies against citrullinated proteins, which are more specific to rheumatoid arthritis in some cases. Rheumatoid factor detects antibodies against immunoglobulin G, which can also appear in other autoimmune or inflammatory conditions.
What if my ACPA levels are high?
High ACPA levels strongly suggest rheumatoid arthritis, but they can also appear in other autoimmune diseases (e.g., psoriatic arthritis) or during infections. Your doctor will consider symptoms, other test results, and clinical findings to interpret results accurately.
Can diet or supplements affect ACPA test results?
Diet or supplements typically do not directly influence ACPA levels, but avoiding anti-inflammatory medications (like ibuprofen) for 24 hours before testing may improve accuracy. Always follow your healthcare provider’s specific instructions.
  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