This is a highly specialized, third-level test for Antiphospholipid Syndrome (APS). While the IgG and IgM antibodies are most common, this test detects the IgA antibodies against cardiolipin. It is a critical part of a comprehensive autoimmune workup, especially when suspicion for APS is high but other tests (like IgG and IgM) are negative. A simple blood draw completes the diagnostic puzzle, ensuring no stone is left unturned in finding the root cause of your symptoms.