Role of antiphospholipid score and anti-β2-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-β2 glycoprotein 1 (aβ2GP1) autoantibodies were tested by ELISA and CIA. Anti-β2GP1 Domain 1 IgG (D1) autoantibodies were tested by CIA. Three aPL-Ss were calculated (ELISA, CIA and CIA with D1 instead of β2GP1 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. aβ2GPI-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.