Introduction: Beta-2-glycoprotein I (B2GPI) is a 50 KD protein cofactor required by anti-cardiolipin antibodies (ACA) to bind to cardiolipin and other phospholipid molecules. ACA have been associated with spontaneous arterial and venous thromboses occurring in patients with systemic lupus erythematosus and the anti-phospholipid antibody syndrome (APS); however not all ACA detected in the laboratory have this association. Some ACA are cross-reactive with anti-bacterial antibodies and others with anti-double-stranded DNA antibodies; therefore they are not highly specific for APS.

Investigations have shown that anti-B2-GPI antibodies are more (but not 100%) specific in identifying patients with "pathogenic" ACA associated with the antiphospholipid syndrome. Both anti-B2GPI IgG and IgM testing are recommended for use in conjunction with traditionally used ACA and lupus anticoagulant tests but should not replace these assays because they are more sensitive. The latest (1999) International Consensus criteria for APS require persistent test positivity after 6 weeks as an indication of "pathogenic" ACA. (Ref: Arthritis and Rheumatism 1999, 42(7):1309-11 and Arthritis and Rheumatism 2000, 43(2) 440-443)

Test methodology: "Sandwich" ELISA.

Reference range: Normal is < 20 units. A result of >20 units is considered positive.

Specimen requirement: Serum, 2 ml. (red top or serum separator tube). Serum must not be hemolyzed, lipemic or contaminated by bacteria or yeast.

Day performed: Thursday.

Test charge: $53.00 each

Questions or comments: James A.Goeken, M.D. (6-1966), John D. Kemp, M.D. (5-8233), Michael Icardi, M.D. (4-8632) or Lisa Horning, SI (ASCP) (6-2846).