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IgG Anti-Cardiolipin Antibody (IgG ACL Antibody) - Immunoassay

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

This test measures the presence of antibodies against cardiolipin, a protein found in cell membranes, which may be linked to certain autoimmune conditions.

Quick summary

["Helps assess potential autoimmune or inflammatory conditions, including lupus or other connective tissue disorders."]

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

Key facts at a glance

LOINC
48890-8
Short code
COXPH1M
Synonyms
C burnet Ph1 IgM Titr Fld IF
Category
chemistry
Sample
serum
Container
Serum separator tube (SST, tiger-top) or plain red-top tube; alternate: plasma from EDTA or heparin tube
Units
N/A
Ref low
0
Ref high
1
Critical range
— – 200 N/A
Fasting
false
Population
adult
Sex
all
Age range
≥ 0 years
Method
Immunofluorescence assay (IFA) for detection of IgM antibodies directed against Phase 1 antigen of Coxiella burnetii
CPT
86638
SNOMED
12196007
Specimen volume
1.0 mL serum (minimum 0.5 mL)
Stability
Stable for 7 days at 2–8°C; for extended storage, freeze at -20°C or below for up to 4 weeks. Avoid repeated freeze-thaw cycles.
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
24–72 hours
Order
routine

What Is This Test Measuring?

Your blood sample is tested for IgG antibodies that target cardiolipin, a fatty acid-protein complex. These antibodies can be detected using an immunoassay method, which identifies their presence through a chemical reaction that produces a measurable signal.

Why Might This Test Be Ordered?

Doctors may order this test if you have symptoms suggestive of autoimmune diseases, such as joint pain, unexplained fatigue, or a history of blood clots or lupus. It can also be part of a broader evaluation for conditions like antiphospholipid syndrome.

Sample Collection and Preparation

A blood sample is drawn from a vein in your arm. The sample is processed to separate serum (the liquid part of blood without clotting factors) for testing. This test does not require fasting.

What Does a Positive Result Mean?

A positive result indicates the presence of IgG antibodies against cardiolipin, which may suggest an autoimmune response. However, this alone does not diagnose a specific condition; further clinical correlation and testing are needed.

Reference range

Titer <1:50: Negative – no detectable Phase 1 IgM antibodies; Titer 1:50–1:100: Equivocal/borderline – recommend repeat testing in 2–4 weeks; Titer ≥1:200: Positive – suggests recent or acute Q fever infection, particularly indicative of chronic Q fever (e.g., endocarditis, vascular infection) when Phase 1 IgG titers are also elevatedN/A

Specimen: serum

No fasting required. Patient should be informed that this test detects antibodies to Coxiella burnetii, the causative agent of Q fever. A second (convalescent) specimen collected 2–4 weeks after the acute specimen is strongly recommended to demonstrate seroconversion or rising titers for accurate diagnosis.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

IgG ACL Antibody

Frequently asked questions

What does a positive result mean for my health?
A positive result means your blood contains antibodies against cardiolipin, which may raise concerns about autoimmune activity. This does not confirm a diagnosis but may prompt further evaluation, including additional tests or a discussion with your doctor about possible conditions like antiphospholipid syndrome or lupus.
How often should I get this test?
Your doctor will determine how often you need this test based on your symptoms, medical history, and other test results. Some patients may need retesting periodically if they have ongoing symptoms or risk factors for autoimmune conditions.
Can lifestyle changes affect this test result?
While certain lifestyle factors like diet or stress management may influence overall health, they typically do not directly affect antibody levels measured in this test. Your doctor will consider all relevant factors when interpreting your results.
  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