Cardiolipin Antibodies IgM Test

The Cardiolipin Antibodies IgM Test is a specialised blood test used to detect immunoglobulin M (IgM) class antibodies directed against cardiolipin, a phospholipid found in cell membranes. It is primarily requested as part of the investigation of antiphospholipid syndrome (APS), a condition characterised by abnormal blood clotting (thrombosis) and/or recurrent pregnancy loss. Your doctor may recommend this test if you have experienced an unexplained blood clot, recurrent miscarriages, or a low platelet count, or if you have an autoimmune condition such as lupus (systemic lupus erythematosus) where APS can occur alongside it. The test is also used to monitor known antiphospholipid syndrome and to assess the risk of thrombosis in certain clinical situations.

This test measures the level of IgM cardiolipin antibodies in your blood. Cardiolipin antibodies are autoantibodies that mistakenly target cardiolipin, a component of the inner mitochondrial membrane. They are one of the three main laboratory criteria for diagnosing antiphospholipid syndrome, alongside lupus anticoagulant and anti-beta-2-glycoprotein I antibodies. The IgM isotype is one of the three antibody classes (IgG, IgM, and IgA) that can be tested; IgM antibodies are typically the first to appear in an immune response and can be transient, so a positive result may need to be confirmed with a repeat test after 12 weeks to establish persistence, as required by the updated Sapporo criteria.

The test is performed on a simple blood sample, which is analysed in the laboratory using an enzyme-linked immunosorbent assay (ELISA) or similar immunoassay technique to quantify the level of IgM cardiolipin antibodies. Results are reported in units (e.g., MPL units) and interpreted alongside your clinical history and other laboratory findings.

Biomarkers included

Antiphospholipid Antibodies
- Cardiolipin antibodies IgM

Why it matters
Identifying IgM cardiolipin antibodies can help explain unexplained thrombosis or pregnancy loss and guide decisions about anticoagulation or other management. It forms part of the diagnostic criteria for antiphospholipid syndrome, a condition that carries significant risks if undiagnosed. Early detection allows your doctor to tailor treatment, monitor your condition, and reduce the chance of serious complications.

Antiphospholipid Antibodies
- Cardiolipin antibodies IgM

No special preparation required.

For blood tests, we recommend drinking plenty of water beforehand to ensure smooth sample collection. If you are taking any regular medication, continue to do so unless advised otherwise by your doctor.