Cardiolipin Antibody IgG (aCL IgG) Biomarker Testing
It checks an antiphospholipid antibody linked to clotting and pregnancy loss, with easy ordering and Quest-network lab collection via Vitals Vault.
With Vitals Vault, you have access to a comprehensive range of biomarker tests.
A Cardiolipin Antibody IgG test (also called anticardiolipin IgG or aCL IgG) looks for an immune protein that can increase your tendency to form abnormal blood clots in some people.
This test is most often used when you have had an unexplained blood clot, certain pregnancy complications, or a history that raises concern for antiphospholipid syndrome (APS). It is not a general “inflammation” test, and a positive result does not automatically mean you have APS.
Because results can be temporary after infections or certain medications, interpretation usually depends on your symptoms, your history, and whether the antibody stays positive when the test is repeated.
Do I need a Cardiolipin Antibody IgG test?
You may want this test if you have had a blood clot that was unexpected for your age or risk profile, such as a deep vein thrombosis (DVT), pulmonary embolism (PE), stroke, or transient ischemic attack (TIA) without a clear trigger. It can also be relevant if you have livedo reticularis (a lace-like purple skin pattern), low platelets, or other findings that make your clinician consider an autoimmune clotting tendency.
This test is also commonly ordered when you have pregnancy complications that can be associated with antiphospholipid antibodies, including recurrent pregnancy loss, unexplained fetal loss later in pregnancy, severe preeclampsia, or placental insufficiency. In those situations, your clinician usually interprets aCL IgG alongside other antiphospholipid antibody tests.
You generally do not need this test as a first step for nonspecific symptoms like fatigue, headaches, or body aches unless there is a clotting or pregnancy-history reason to look for APS. If your result is abnormal, the next step is typically confirmation and context, not self-diagnosis—your clinician uses it as one piece of your overall risk assessment and care plan.
This is a blood immunoassay performed in a CLIA-certified laboratory; results support clinical decision-making but do not diagnose antiphospholipid syndrome on their own.
Lab testing
Order labs to measure Cardiolipin Antibody (IgG)
from $24.99 at Quest Diagnostics
About 1 week
Schedule online — results typically within a week
Clear next steps
Guidance included, with follow-up care available
HSA / FSA
Eligible for pre-tax health spending accounts
Get this test with Vitals Vault
Vitals Vault lets you order Cardiolipin Antibody IgG testing directly, then complete your blood draw at a Quest-network collection site. You can use the result to prepare for a clinician visit, to confirm a prior abnormal finding, or to help map out what additional clotting or autoimmune tests make sense.
After your result posts, PocketMD can help you translate the report into plain language and generate questions to bring to your clinician—especially around whether the level is meaningfully elevated, whether it should be repeated, and what companion tests (like lupus anticoagulant and beta-2 glycoprotein I antibodies) are typically checked.
If you are tracking an abnormal result over time, Vitals Vault makes it easier to retest with the same ordering flow so you can see whether the antibody persists, which is a key part of how APS is evaluated.
- Order online and draw at a Quest-network location
- Clear, shareable results you can bring to your clinician
- PocketMD guidance for next steps and retest timing
Key benefits of Cardiolipin Antibody IgG testing
- Helps evaluate whether antiphospholipid antibodies could be contributing to unexplained blood clots.
- Adds important context in workups for recurrent pregnancy loss or placenta-related pregnancy complications.
- Supports APS assessment when interpreted with lupus anticoagulant and beta-2 glycoprotein I antibodies.
- Distinguishes a one-time, transient antibody signal from a persistent pattern that may matter clinically.
- Guides conversations about prevention strategies if you have other clotting risks or a strong personal history.
- Provides a baseline you can compare against repeat testing (persistence over time is often the key question).
- Pairs well with PocketMD so you can turn a complex immunology result into actionable follow-up questions.
What is Cardiolipin Antibody IgG?
Cardiolipin is a type of phospholipid (a fat-like molecule) found in cell membranes. Cardiolipin antibodies are autoantibodies—immune proteins that mistakenly target your own tissues. The IgG subtype (aCL IgG) is one of the main antiphospholipid antibodies measured when clinicians evaluate antiphospholipid syndrome (APS).
In APS, antiphospholipid antibodies are associated with a higher risk of abnormal clotting in veins or arteries and with certain pregnancy complications. The exact biology is complex, but the practical takeaway is that these antibodies can interact with clotting pathways and the lining of blood vessels, creating a pro-thrombotic (clot-promoting) environment in some people.
A single positive aCL IgG result does not automatically mean you have APS. Many labs report low, moderate, or high positivity, and clinical significance depends on the level, whether it persists on repeat testing, and whether you have APS-related clinical events (such as thrombosis or specific pregnancy outcomes).
How this test fits into APS criteria
APS is typically evaluated using both clinical history (for example, a documented clot or qualifying pregnancy complication) and laboratory evidence. Laboratory evidence usually includes one or more of the following: anticardiolipin antibodies (IgG and/or IgM), anti–beta-2 glycoprotein I antibodies (IgG and/or IgM), and lupus anticoagulant testing. Persistence is important: many clinicians repeat positive antibody tests after at least 12 weeks to see if the finding is sustained.
IgG vs IgM vs IgA
IgG and IgM are the most commonly used isotypes in APS evaluation. IgG positivity is often considered more strongly associated with clinical events than low-level IgM, but your overall pattern matters more than any single number. Some labs also offer IgA testing in select situations, but it is not always part of standard criteria-based evaluation.
What do my Cardiolipin Antibody IgG results mean?
Low (negative) Cardiolipin Antibody IgG
A low or negative result means the lab did not detect a clinically significant level of anticardiolipin IgG at the time of testing. This lowers the likelihood that aCL IgG is contributing to clotting or pregnancy complications, but it does not rule out APS by itself. If suspicion remains high, clinicians often check the other antiphospholipid tests (lupus anticoagulant and beta-2 glycoprotein I antibodies) because some people are negative on one marker and positive on another.
In-range (negative) or borderline results
Many reports include a borderline or low-positive zone. Borderline results can happen transiently, especially around infections or inflammatory stress, and they are often not treated as diagnostic on their own. If your result is borderline and your history suggests possible APS, your clinician may recommend repeating the test after time has passed and ordering companion antiphospholipid antibodies to look for a consistent pattern.
High (positive) Cardiolipin Antibody IgG
A high or clearly positive result means you have measurable anticardiolipin IgG antibodies. The higher the level and the more consistently it remains positive on repeat testing, the more likely it is to be clinically meaningful—especially if you have had a documented clot or qualifying pregnancy complication. A positive result is a prompt to review your full history, consider confirmatory repeat testing (often at least 12 weeks later), and evaluate the rest of the antiphospholipid antibody panel rather than acting on a single marker alone.
Factors that influence Cardiolipin Antibody IgG
Anticardiolipin antibodies can rise temporarily after viral or bacterial infections, and they may fluctuate over time. Different laboratories and assay methods can also produce slightly different numeric values, so trending is most useful when you repeat testing in a consistent setting. Anticoagulant medications can interfere with lupus anticoagulant testing (a different APS test), but they do not typically invalidate anticardiolipin antibody measurements; still, your medication list and timing should be reviewed with your clinician. Autoimmune diseases such as lupus (SLE) can increase the chance of antiphospholipid antibody positivity, which is why clinicians often interpret aCL IgG alongside broader autoimmune and clotting evaluations.
What’s included
- Cardiolipin Ab (Igg)
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Frequently Asked Questions
Do I need to fast for a Cardiolipin Antibody IgG test?
Fasting is not usually required for anticardiolipin antibody testing. If you are combining it with other labs (like lipids or glucose), follow the fasting instructions for the full set of tests you are ordering.
What is a normal range for cardiolipin IgG?
“Normal” depends on the lab and the assay, so your report’s reference interval is the one to use. Many labs report categories such as negative, borderline/indeterminate, and positive (sometimes with low, moderate, or high positivity). The clinical meaning depends on the level and whether it persists on repeat testing.
If my cardiolipin IgG is positive, do I have antiphospholipid syndrome (APS)?
Not necessarily. APS is usually diagnosed based on both clinical criteria (such as a documented clot or specific pregnancy complications) and persistent laboratory positivity, often confirmed by repeating testing at least 12 weeks apart. A single positive aCL IgG result is a reason to follow up, not a diagnosis by itself.
When should I repeat a positive anticardiolipin IgG test?
Clinicians often repeat antiphospholipid antibody tests after at least 12 weeks to confirm persistence, because temporary positivity can occur. Your exact timing should be individualized based on your symptoms, pregnancy plans, and whether you are being evaluated after a recent infection or acute event.
What other tests are usually ordered with cardiolipin IgG?
Common companion tests include lupus anticoagulant testing and anti–beta-2 glycoprotein I antibodies (IgG and IgM). Many clinicians also check cardiolipin IgM (and sometimes IgA) to see the full antibody pattern, and they may order additional clotting or autoimmune labs depending on your history.
Can an infection cause a false positive cardiolipin IgG?
Infections can cause transient antiphospholipid antibody positivity, which is one reason repeat testing is often recommended before labeling a result as persistent. If you were recently ill, tell your clinician so they can interpret the timing appropriately.
Is cardiolipin IgG the same as lupus anticoagulant?
No. Cardiolipin IgG is an antibody measured by an immunoassay, while lupus anticoagulant is a functional clotting test that looks for a specific pattern of interference in coagulation assays. They are related because both are part of APS evaluation, but they are different tests and can be discordant.