Unlike cardiolipin, phosphatidylserine is a more physiologically relevant phospholipid due to its presence in cell membranes of endothelial cells and platelets and its role in the coagulation cascade. The detection of antiphosphatidylserine (aPS) antibodies by ELISA has been recommended for the serological diagnosis of antiphospholipid syndrome. Patients with positive reactions to both cardiolipin and phosphatidylserine are more likely to have clinical complications than those positive for only one. Higher prevalence and mean serum levels of antiphosphatidylserine antibodies have been reported in autoimmune patients. In addition, antiphosphatidylserine antibodies in SLE patients correlated with clinical manifestations of antiphospholipid syndrome and their pathogenic role has been demonstrated in a murine model.

Reference Ranges:

Phosphatidylserine Ab IgG
<10    Negative
10-20    Equivocal - Found in small percentage of the healthy population; may be reactive
>20    Positive - Risk factor for thrombosis and pregnancy loss

Phosphatidylserine Ab IgA
<20    Negative
20-30    Equivocal - Found in small percentage of the healthy population; may be reactive
>30    Positive - Risk factor for thrombosis

Phosphatidylserine Ab IgM
<25    Negative
25-35    Equivocal - Found in small percentage of the healthy population; may be reactive
>35    Positive - Risk factor for thrombosis

IgG and/or IgM antibodies to phosphatidylserine (aPS) may be associated with a positive test for anti-cardiolipin autoantibodies (aCL) and risk for obstetric antiphospholipid syndrome (APS). Strong clinical correlation is recommended in the absence of lupus anticoagulant, IgG and/or IgM cardiolipin and/or beta2 glycoprotein antibodies.

Isolated presence of IgM or IgG antibodies to aPS may have questionable clinical significance for APS and/or SLE.

If results are positive, repeat testing with two or more specimens drawn at least 12 weeks apart to demonstrate persistence of antibodies.

Results should not be used alone for diagnosis and must be interpreted in light of APS-specific clinical manifestations and/or other criteria phospholipid antibody tests.

Antiphospholipid antibodies are a heterogeneous group of immunoglobulins that bind to several anionic phospholipids, includingn cardiolipin and phosphatidylserine.