Résumé
OBJECTIVE: To investigate the autoantibody profile and its clinical association in patients with systemic lupus erythematosus. METHODS: The frequency and clinical correlation of autoantibodies were studied in 73 patients with systemic lupus erythematosus who have been followed in Seoul National University Hospital. Double immunodiffusion, ELISA and immunoblot were used for the detection of autoantibodies. RESULTS: The frequency of each autoantibody measured by double immunodif fusion was as follows; anti-Ro 53.4%, anti-La 11.0%, anti-Sm 20.5%, anti-U1 RNP 20.5%. The frequency of each autoantibody by ELISA was as follows; anti-Ro 69.9%, anti-La 27.4%, anti-Sm 54.8%, anti-Ul RNP 68.5%, anti-dsDNA 72.6%, anti-cardiolipin 47.2% (IgG 43.1?0, igM 15. 3%). The frequency of each autoantibody by immunoblot was as follows; anti-Ro 15.1?0, anti-La 42. 5%, anti-Sm 46. 6%, anti-U1 RNP 42. 5%. anti-ribosomal P(P0) 27.4%. Anti-Ro was associated with decreased frequency of nephrotic syndrome. Anti-U1 RNP was associated with increased frequency of malar rash, Raynaud phenomenon and decreased frequency of nephritis. Patients with both anti-Ro and anti La had more frequent serositis than those with anti-l~o only. Patients with both anti-Sm and anti-U1 RNP had less frequent thrombocytopenia than those with anti-U1 RNP only. And patients with anti-Sm and anti-dsDNA had more frequent arthritis than those with only one of both antibodies. There was a positive correlation of autoantibody titers between anti-Ro and anti-La, anti-Sm and anti-U1 RNP, anti-dsDNA and anti-cardiolipin(IgG). Taking the result of immunoblot as a standard, both of double immunodiffusion and ELISA showed low sensitivity but high specficity for anti La. As for anti-Sm and anti-U1 RNP, double immunodiffusion showed low sensitivity but high specificity, whereas ELISA showed high sensitivity but low specificity. CONCLUSIONS: In our study, some autoantibodies (anti-Ro, anti-U1 RNP) were associated with certain clinical manifestations while others not. Immunoblot being used as a standard method, ELISA showed higher sensitivity but lower specificity for anti-La, anti-Sm and anti-U1 RNP compared with immunodiffusion. It is recommended that in interpretating the laboratory findings of these autoantibodies these parameters of each method should be considered.