Autoantibodies and pregnancy loss

This chapter describes recent studies that investigated the possible influences of autoimmune factors in pregnancy loss. At present, it seems that there are various antibodies associated with pregnancy loss. These include antiphospholipid antibodies (APS), antithyroid antibodies and antinuclear antibodies. Systemic lupus erythematosus (SLE) and diabetes mellitus are two autoimmune diseases that have been associated with pregnancy loss. Some patients with SLE or APS have autoantibodies mainly directed to phospholipids such as cardiolipin, phosphatidylserine, phosphatidylethanolamine, or phospholipids binding glycoproteins such as β2glycoprotein-I, annexin V, prothrombin, and protein-Z. Future studies may define other autoantibodies. APS was first detected by their effect on coagulation. Hence, the first antibody to be detected was named "lupus anticoagulant" (LA). LA seems to be the most specific test for APS. Diagnosis in vitro depends on prolongation of the phospholipid-dependent coagulation tests such as prothrombin time, recalcification time, and the kaolin clotting time (KCT). Most units use the activated partial thromboplastin test (APTT) as a diagnostic test as it is the most readily available. The dilute Russell's viper venom test (dRVVT) seems to be more sensitive than the previously used KCT, and has tended to replace it. The antibody can be examined directly (rather than by its effect on clotting), by using the enzyme-linked immunoabsorbtion assay (ELISA), with cardiolipin as the antigen. However, the test is not specific when results are low positive. In general, the higher the anticardiolipin level the greater the likelihood of APS. The presence of anti β2GP1antibodies may be more relevant than the other two antibodies. Although anti β2GP1 antibodies have high specificity for APS (98%), their assessment cannot be entirely relied upon in normal clinical practice as the sensitivity of testing is low.