Objectives: Clinical and immunological features of patients with clinical manifestations of the antiphospholipid syndrome (APS) with anti-beta2-glycoprotein-I antibodies (anti-beta2-GP-I) but without anticardiolipin antibodies (aCL) or any other autoimmune condition are not well documented. We sought to determine the clinical significance of positive anti-beta2-GP-I with negative aCL.
Methods: From July 2002 through July 2003, 1,179 serum samples obtained in our hospital from the Community of Madrid were tested for anti-beta2-GP-I and aCL by enzyme-linked immunosorbent assay. Clinical records of patients with discordant anti-beta2-GP-I and aCL were retrospectively analysed.
Results: A total of 56 patients with discordant anti-beta2-GP-I and aCL were identified. By logistic regression analysis, after adjusting for age, sex and risk factors of thrombosis, the risk for developing APS criteria associated with anti-beta2-GP-I was significant [odds ratio 3.88; 95% confidence interval (CI): 1.05-14.27; p = 0.04). 15 out of 56 patients (26.8%) had positive anti-beta2-GP-I and negative aCL. 5 out of 15 anti-beta2-GP-I-positive patients had clinical APS without serological nor clinical evidence of any autoimmune disease.
Conclusion: Determination of anti-beta2-GP-I should be considered in individual cases with clinical manifestations of primary APS and repeated negative results on conventional antiphospholipid antibody test.