Skip to content

Anti-Citrullinated Protein Antibody (ACPA) by Immunoassay

Published: August 9, 2026Updated: August 17, 2026

This test measures antibodies against citrullinated proteins, 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 17, 2026Editorial policy

Key facts at a glance

LOINC
43623-8
Short code
AChR Block Ab Ser Ql
Synonyms
AChR Block Ab Ser Ql
Category
coagulation
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
22
Ref high
198
Critical range
— – 10000 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82553
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 target proteins modified by the enzyme citrulline, which occurs naturally in the body. These antibodies are often found in people with rheumatoid arthritis or other inflammatory joint diseases.

Why Might Your Doctor Order This Test?

Your doctor may recommend this test if you have symptoms like joint pain, swelling, or stiffness—especially if they suspect rheumatoid arthritis or another autoimmune disorder.

How Is This Test Performed?

A blood sample is drawn, and the serum is tested using an immunoassay method to detect ACPA antibodies.

What Does a Positive Result Mean?

A positive result suggests a higher likelihood of rheumatoid arthritis or related conditions, but it doesn’t confirm a diagnosis alone. Results are often interpreted alongside other clinical findings.

Reference range

Adult males: 22-198 U/L; Females: 22-198 U/LN/A

Specimen: serum

No special preparation required. Inform provider of any chest pain or symptoms.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

ACPA Antibody

Frequently asked questions

Why do I need this test if I don’t have symptoms yet?
This test may be used as a screening or monitoring tool in high-risk groups (e.g., family history of rheumatoid arthritis) or during routine check-ups if symptoms develop later.
Can this test be used to monitor treatment progress?
Yes, ACPA levels can sometimes change with treatment, helping doctors assess how well your condition is responding to medications.
Are there any risks or side effects from this blood test?
The only minor risk is mild bruising or discomfort at the needle site, which is rare. No other side effects are expected.
  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 17, 2026. · Read our editorial policy