Alternative name:
Description: A complex group of autoantibodies associated with thrombosis (arterial and venous) in primary anti-phospholipid syndrome and connective tissue disease, particularly SLE, where anti-cardiolipin antibodies are frequently, but not always, the cause of lupus anticoagulant activity. The antibodies are found more commonly in patients who do not have lupus and are associated, somewhat paradoxically, with unexplained venous and arterial thrombosis, myocardial infarction, neurological symptoms, strokes in young patients and with recurrent abortion.Although anti-cardiolipin antibodies are the most commonly measured, it has been recognised that they are only one group of several specificities of anti-phospholipid autoantibodies found in these patients. The autoantibodies are better defined as anti-phospholipid antibodies. Their detection has led to the definition of a new disease entity, the anti-phospholipid syndrome (APS).Antiphospholipid syndrome is thought to be manifested by a wide range of symptoms. Anti-phospholipid antibodies are also found in a number of infectious diseases and also in some patients with cancer. Anti-cardiolipin antibodies were reported to be the anti-M1 mitochondrial antibodies. They are responsible for the false positive VDRL (syphilis) test occasionally seen in lupus patients. Anticardiolipin antibodies associated with APS most commonly recognise a serum protein b2-glycoprotein 1 associated with phospholipid. The assay used in this laboratory contains b2-glycoprotein 1. Infection-related anticardiolipin antibodies are thought not to involve b2-glycoprotein 1.Anti-cardiolipin autoantibodies can be any combination of IgG, IgM and IgA classes. IgG antibodies are the most prevalent class of autoantibody and the class with the greatest clinical correlation. Samples found to high levels of IgG anti-cardiolipin are the most likely to display overt clinical symptoms. However, IgA and IgM autoantibodies are often found either alone or combination with the IgG. IgG and IgM anticardiolipin antibodies are measured in this laboratory. Antibody concentrations do not correlate with extent or severity of thrombosis.

Anti-cardiolipin can be positive in patients without major thrombotic problems. Anti-cardiolipin antibodies, the lupus anticoagulant test and the VDRL detect overlapping but not identical populations of antibodies. Anti-cardiolipin antibodies and lupus anticoagulant activity (haematology test) should be measured. The two assays do not always agree

Indication: Investigation of Primary anti-phospholipid syndrome & thrombosis associated with SLE and other connective tissue diseases; neurological events; pregnancy associated disorders including recurrent and post natal thrombosis and thrombosis. Investigation of unexplained thrombocytopaenia.
Interpretation: Anti-cardiolipin antibodies are by definition a major criterion for a diagnosis of APS. They are found in around 30-40% of patients with SLE. In both patients with primary and SLE associated APS positive results correlate with a predisposition for arterial or venous thrombosis, foetal loss, or thrombocytopoenia. However, levels of anti-cardiolipin antibodies do not correlate well with disease activity or with specific features of SLE such as arthritis or renal involvement.Nevertheless, the presence of these autoantibodies serves as a marker for the risk of a thromboembolitic event. Those SLE patients exhibiting high levels of these autoantibodies are 4 times more likely to have such an event than those not expressing the autoantibodies.Anti-cardiolipin antibodies are associated with recurrent spontaneous abortion and with thrombotic events in mothers shortly after birth. They are also found in up to 20% of young stroke patients.Anti-phospholipid antibodies are also found in infections including syphilis, malaria, parasitic diseases and infectious mononucleosis. Indeed,anticardiolipin antibodies can be transiently elevated in many infections. For this reason , positive results should always be confirmed after 8 -12 weeks.
Sample: Serum Separator Tube (SST)
Assay details: Fluorescence enzyme linked immunoassay (Phadia Immunocap 250).
restrictions: Always request lupus anticoagulant at the same time (haematology test).
Reference range: IgG anticardiolipin:

  • Weak positive: 15-40U/ml
  • Positive: >40U/ml

IgM anticardiolipin:

  • Weak positive: 15-40U/ml
  • Positive: >40 U/ml
Assay range notes: IgG anticardiolipin:

  • Weak positive: 15-40U/ml
  • Positive: >40U/ml

IgM anticardiolipin:

  • Weak positive: 15-40U/ml
  • Positive: >40 U/ml
Turnaround time: 3 – 5 days
Analysing laboratory: Immunology The James Cook University Hospital