Blood clotting Biomarker
Collection Type: Blood
Related System: Blood clotting
Anti‑cardiolipin IgA (aCL IgA) is an autoantibody directed against cardiolipin, a phospholipid present on cell membranes and platelets. The test measures IgA-class anticardiolipin antibodies, usually by ELISA, as part of antiphospholipid antibody evaluation. Elevated aCL IgA can be associated with antiphospholipid syndrome (APS), unexplained arterial or venous thrombosis, recurrent pregnancy loss, and some autoimmune diseases (eg, systemic lupus erythematosus). Symptoms prompting testing include unexplained clots, recurrent miscarriages, stroke at a young age, or persistent thrombocytopenia. IgA results may vary by age and sex (more often tested in women with pregnancy loss) and can be transiently positive after infections, medications, or vaccination.
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Q: What does anticardiolipin IgA test for?
A: The anticardiolipin IgA test detects IgA-class antiphospholipid antibodies directed against cardiolipin. It helps identify autoimmune risk for antiphospholipid syndrome—linked to arterial or venous blood clots, recurrent pregnancy loss and low platelets. IgA is measured when IgG/IgM are negative or in certain clinical contexts. Positive results require confirmation after 12 weeks and correlation with symptoms and other antiphospholipid tests.
Q: What does a positive anti cardiolipin antibody mean?
A: A positive anti‑cardiolipin antibody indicates the immune system is producing antibodies against phospholipids. It can be associated with antiphospholipid syndrome, which raises the risk of blood clots and pregnancy complications (recurrent miscarriage, preeclampsia). Single positives may be transient after infection or drugs; persistence (repeat testing after ≥12 weeks) and clinical history determine significance and need for treatment, such as anticoagulation.
Q: What is the normal range for anticardiolipin IgA?
A: Anticardiolipin IgA is usually reported in units; a normal (negative) result is typically <20 U/mL (or <20 APL units). Results 20–40 U are often considered borderline, while >40 U (or >99th percentile) is regarded as positive and clinically significant (medium–high titre) for antiphospholipid syndrome. Positive tests are generally repeated after about 12 weeks.
Q: What if cardiolipin ab IgA is not detected?
A: If cardiolipin IgA is not detected, there’s no evidence of anti‑cardiolipin IgA on that test. It doesn’t exclude antiphospholipid syndrome—other antibodies (cardiolipin IgG/IgM, beta‑2 glycoprotein, lupus anticoagulant) may be present. If clinical suspicion (thrombosis, recurrent pregnancy loss) remains, repeat testing after 12 weeks and discuss further evaluation with your clinician, since timing and lab variability can affect results.
Q: Does anticardiolipin IgA indicate risk of clotting?
A: Anticardiolipin IgA can be associated with thrombosis but is not part of formal antiphospholipid syndrome classification, so its significance is less certain than IgG/IgM. Persistent, moderate-to-high titers and accompanying clinical events or other antiphospholipid antibodies raise concern. Isolated low‑titer IgA warrants repeat testing after 12 weeks and specialist review to assess thrombotic risk and management.
Q: Can anticardiolipin IgA be positive temporarily due to infection?
A: Yes. Anticardiolipin IgA, like other antiphospholipid antibodies, can be transiently positive during acute infections (viral or bacterial) without indicating antiphospholipid syndrome. Diagnosis requires persistent positivity on repeat testing at least 12 weeks apart plus clinical criteria (thrombosis or pregnancy complications). Transient elevations often resolve after recovery and generally carry lower long‑term thrombotic risk, so clinicians repeat tests later.