Objective: Studies in rheumatologic populations suggest that immunoglobulin A antiphospholipid antibodies are strongly associated with the clinical manifestations of antiphospholipid syndrome. However, the association between immunoglobulin A antiphospholipid antibodies and pregnancy loss is uncertain. We determined whether immunoglobulin A antiphospholipid antibodies, specifically anti-beta(2)-glycoprotein I and anticardiolipin, are associated with the obstetric features of antiphospholipid syndrome.
Study design: Sera from 4 groups of women were studied: (1) 133 women who experienced unexplained recurrent spontaneous abortion, (2) 48 women who experienced unexplained fetal death, (3) 145 healthy fertile control subjects, and (4) 67 women with well-characterized antiphospholipid syndrome. Serum immunoglobulin A, immunoglobulin G, and immunoglobulin M anti-beta(2)-glycoprotein I and anticardiolipin antibodies were determined by enzyme-linked immunoassay.
Results: Groups of women who experienced unexplained recurrent spontaneous abortion and unexplained fetal death had a higher proportion of women who had positive test results for immunoglobulin A anti-beta(2)-glycoprotein I antibodies than fertile control subjects (P < .01, chi-square test); these subjects also had higher levels of autoantibody (P = .001, Kruskal-Wallis). Women who experienced recurrent spontaneous abortion had a higher proportion of women with positive test results for immunoglobulin A anticardiolipin antibodies compared to fertile control subjects (P < .05, chi-square test); this group also had higher levels of autoantibody (P = .0065, Kruskal-Wallis test). Linear regression analysis showed significant correlation between anti-beta(2)-glycoprotein I immunoglobulin A and anti-beta(2)-glycoprotein I immunoglobulin G (R = .609; P =.0001) and less correlation between anticardiolipin immunoglobulin A and anticardiolipin immunoglobulin G (R = .093; P = .065).
Conclusion: Immunoglobulin A anti-beta(2)-glycoprotein I antibodies are more common in women who experience unexplained recurrent spontaneous abortion and unexplained fetal death whose initial test results are negative for lupus anticoagulant and immunoglobulin G anticardiolipin antibodies compared to fertile control subjects. Therefore, these antibodies may identify additional women with clinical features of antiphospholipid syndrome who are not identified through traditional testing. It is unclear whether these antibodies are directly pathogenic, a result of the pregnancy losses, or markers for an underlying, yet uncharacterized autoimmune disorder.