Role of antiphospholipid score and anti-ß2-glycoprotein I Domain I autoantibodies in the diagnosis of antiphospholipid syndrome.

BACKGROUND: Antiphospholipid syndrome (APS) is characterized by the presence circulating antiphospholipid (aPL) antibodies in patients with thrombosis or pregnancy morbidity. Recently it has been shown that multiple positive results define a higher risk of clinical manifestation in APS patients. However, utilizing combined results generates challenges for a physician. Therefore, the antiphospholipid score. (aPL-S), a new variable that encompasses all aPL assays, has been described. We analyze clinical performance of different aPL-Ss based on ELISA or chemiluminescent immunoassays (CIAs). METHODS: A total of 39 patients and 77 controls were included in this study. All patients were tested for lupus anticoagulant (LAC). In addition, IgM/IgG anticardiolipin (aCL) and anti-ß2 glycoprotein 1 (aß2GP1) autoantibodies were tested by ELISA and CIA. Anti-ß2GP1 Domain 1 IgG (D1) autoantibodies were tested by CIA. Three aPL-Ss were calculated (ELISA, CIA and CIA with D1 instead of ß2GP1 IgG) using the Otomo equation: aPL-S=5×exp([OR]-5)/4. RESULTS: IgG assays showed a good correlation while IgM assays showed moderate correlation. The relative risk of having clinical manifestation of APS was calculated for each aPL test. All three aPL-Ss were higher in individuals with thrombosis or pregnancy morbidity than in those without APS manifestations (p<0.001) and the prevalence of APS manifestations increased with increasing aPL-Ss. CONCLUSION: The CIAs are comparable with the ELISAs for the detection of aPL antibodies. aß2GPI-D1 antibodies seem to represent a strong indicator for clinical manifestations of APS. Any of the aPL-Ss studied represents a useful quantitative index for APS diagnosis and could be helpful to physicians in managing APS.