Prevalence and isotype distribution of antiphospholipid antibodies in Chilean patients with systemic lupus erythematosus (SLE)

Previous studies have demonstrated that ethnicity plays a role in the preva lence, isotype distribution, and clinical significance of anticardiolipin ( aCL) and anti-beta (2) glycoprotein I (a beta (2)-GPI) antibodies in system ic lupus erythematosus (SLE) patients. Few studies have been done in Latin American populations. Serum samples from 129 Chilean SLE patients were test ed for IgG, IgM and IgA aCL and a beta (2)-GPI by ELISA. Clinical data were reviewed with the focus on clinical manifestations of antiphospholipid syn drome (APS). Positivity for at least one isotype of aCL was found in 30% of patients, while only 10% were positive for at least one isotype of a beta (2)-GPI. IgG was the most prevalent isotype for aCL (16%), and the isotype distribution was similar (4%) for a beta (2)-GPI. In general, the presence of aCL was significantly associated with the presence of a beta (2)-GPI, bu t a number of samples were positive for only one antibody, some of them ass ociated with clinical manifestations of APS. ACL antibodies at medium-high titers were significantly correlated with thrombosis (P=0.0007) and fetal l oss (P=0.009); however, the sensitivity of a beta (2)-GPI for detecting thr ombosis and fetal loss was lower than aCL (19 and 17% vs 56 and 50%, respec tively), and the specificity slightly higher (91 and 90% vs 84 and 82%). In Chilean SLE patients, aCL and a beta (2)-GPI antibodies are important in t he evaluation of patients with APS. However, the utility of a beta (2)-GPI antibodies was limited by the low prevalence of these antibodies in compari son with other ethnic groups. Further studies are needed to define the basi s of the observed differences among ethnic groups.