Phospholipid Screen IgG, IgM

Function

The Phospholipid Screen (specifically Cardiolipin antibodies) detects autoantibodies produced by the immune system that mistakenly target the body's own phospholipids. Phospholipids are essential lipid components of cell membranes and platelets. When these antibodies are present, they can interfere with the blood clotting process, paradoxically increasing the risk of inappropriate clot formation (thrombosis).

Why it is Ordered

This test is a critical component in the diagnosis of Antiphospholipid Syndrome (APS). It is typically ordered when a patient experiences unexplained blood clots (Deep Vein Thrombosis or Pulmonary Embolism), recurrent miscarriages (especially in the second or third trimester), or an unexplained prolonged PTT (Partial Thromboplastin Time) test. It is also used to evaluate patients with Systemic Lupus Erythematosus (SLE), as these antibodies frequently co-occur.

Associated Conditions

• Antiphospholipid Syndrome (APS): A systemic autoimmune disorder characterized by arterial or venous thrombosis.
• Systemic Lupus Erythematosus (SLE): Many Lupus patients carry these antibodies, increasing their risk for stroke.
• Recurrent Pregnancy Loss: The antibodies can interfere with placental attachment and blood flow.
• Thrombocytopenia: Low platelet counts caused by antibody-mediated destruction.

Interpretation Nuances

Clinicians look at two classes of antibodies: IgG and IgM. IgG is generally considered more clinically significant for predicting thrombotic events. Because these antibodies can appear transiently during infections (like syphilis or certain viral illnesses), a diagnosis of APS requires two positive tests at least 12 weeks apart.