Sensitivity and Specificity of Immunoglobulin A Isotype of Anti-β2 Glycoprotein I in Patients with Systemic Lupus Erythematosus and Secondary Antiphospholipid Syndrome

Introduction: Systemic lupus erythematosus (SLE) is an autoimmune disease of chronic course characterized by the presence of autoantibodies to the cell nucleus. Antiphospholipid syndrome (APS) is considered the most common cause of acquired thrombophilias. The diagnosis of APS is made on the presence of clinical manifestations of thrombosis/pregnancy morbidity as well as persistently positive antiphospholipid antibodies (aPL) of ant type i.e. anticardiolipin (aCL) IgM/IgG or anti-β2 glycoprotein I (anti-β2GPI) (IgM/IgG) or lupus anticoagulant (LA). Aim of the Work: Identifying the sensitivity and specificity of anti-β2-GPI of IgA isotype among Egyptian SLE patients having and lacking APS. Patients and Methods: The study was done on 54 SLE patients. Twenty seven (50%) of patients had no APS while others had secondary APS. Patients having other known forms of thrombophilia were excluded. Twenty seven apparently normal control persons of matched age and sex were included. Clinical assessment and routine laboratory tests were done. Patients and controls were assessed for positivity of lupus anticoagulant, anti-β2GPI of IgM, IgG and IgA isotype in addition to aCL of IgM, IgG and IgA isotypes. Results: IgA isotype of anti-β2GPI antibodies had a low specificity but high sensitivity in Egyptian lupus patients. Conclusion: Anti-β2GPI of IgA isotype could be considered in assessing lupus patients for APS when the all standardized aPL are negative owing to its high sensitivity.