Determination of Ig M to cardiolipin in blood serum by indirect immunofluorescence

Anti-cardiolipin antibodies (ACA) belong to the group of antiphospholipid antibodies (aPL).

Their occurrence was first demonstrated in the serum of patients with syphilis, but later they were also described frequently in patients with SLE (systemic lupus erythematosus) (prevalence 30-40%) and in patients with other rheumatic diseases.

Antiphospholipid syndrome (APS), also known as Hughes syndrome, is characterized by typical clinical features such as arterial/venous thrombosis or recurrent miscarriages as well as persistently positive tests for aPL. In contrast to “secondary APS”, which occurs in association with SLE or other rheumatic disorders, there is no evidence for another relevant underlying disease in primary APS. New classification criteria for antiphospholipid syndrome have recently been defined.

Anti-cardiolipin antibodies in infectious diseases and APS can be distinguished with respect to their cofactor dependence. Whereas ACA in patients with infectious diseases recognizes pure phospholipid as antigen, ACA binding in patients with APS requires β2-glycoprotein I as cofactor. For this reason, ACA ELISA need β2-glycoprotein I to be included in the test. The so-called lupus anticoagulant (LA) describes the phenomenon associated with the presence of antiphospholipid antibodies. It is determined by measuring antibody-dependent inhibition of coagulation in vitro.

ACA/LA are considered to be of significant diagnostic relevance because of the correlation found between these antibodies and the tendency to thrombosis. This leads to increased rates of venous/arterial thrombosis (including apoplexy), thrombocytopenia, and live reticularis in ACA/LA-positive patients.