CARDIOLIPIN ANTIBODY (ACL) - IgG

Anticardiolipin IgG detects IgG-class autoantibodies against cardiolipin, a phospholipid present in mitochondrial membranes and on activated platelets. These antibodies bind cardiolipin-protein complexes (predominantly β2-glycoprotein-1) and contribute to a pro-thrombotic state — the central abnormality of antiphospholipid syndrome (APS).

The test is a quantitative ELISA reported in GPL units per mL (IgG phospholipid units). It is one of the three primary laboratory criteria of the 2023 ACR/EULAR APS classification, alongside lupus anticoagulant and anti-β2-glycoprotein-1 IgG.

IgG aCL is the single most predictive antibody for thrombotic complications in APS. Patients with high-titre IgG aCL face elevated risk of deep vein thrombosis, pulmonary embolism, stroke in young adults, recurrent miscarriage, and severe pregnancy complications. Identifying these antibodies changes treatment dramatically — patients with prior thrombosis need long-term anticoagulation (warfarin preferred over DOACs), and pregnant women benefit from aspirin + low molecular weight heparin to dramatically improve live birth rates.

In Indian rheumatology practice, IgG aCL is a standard part of the workup for: unexplained venous or arterial thrombosis (especially in young patients), unusual-site thrombosis (cerebral venous sinus, splanchnic, portal vein), recurrent first-trimester miscarriage (≥3), one or more late pregnancy losses, severe pre-eclampsia, and lupus patients planning pregnancy. The 2023 criteria require persistence — a single positive must be confirmed at ≥12 weeks before APS diagnosis is made, because transient positivity occurs after viral infections, certain medications, and acute illness.

No fasting required. Continue all medications including anticoagulants — warfarin, DOACs, and heparin do not interfere with anticardiolipin antibody testing (unlike lupus anticoagulant testing).