Comparison of counter immunoelectrophoresis with immunoblotting for detection of anti-extractable nuclear antigen antibodies in systemic lupus erythematosus

Anti-extractable nuclear antigen (ENA) antibodies were assayed by counter i mmunoelectrophoresis (CIE) and immunoblotting in patients with systemic lup us erythematosus (SLE). We found the two methods showed good concordance ra tes, the lowest being 67% for anti-SS-A. Immunoblotting was more sensitive in detecting anti-Sm, anti-SS-B and anti-PCNA (proliferating cell nuclear a ntigen); CIE was more sensitive for anti-nRNP and anti-SS-A. Overall, the p revalence of these anti-ENA antibodies in SLE was increased by 9-20% if imm unoblotting was used in addition to CIE. Sera specific for the 52 kDa pepti de of the SS-A antigen (anti-52kDa SS-A) were better detected by immunoblot ting, Anti-PCNA antibody was found in 6.3% of SLE patients and was associat ed with active disease and hemolytic anemia. The positive rate of anti-Sm w as 9% by CIE and 23.7% by immunoblotting and this antibody was a specific m arker for SLE using either method. It was concluded that using immunoblotti ng in addition to CIE, the overall sensitivity of detection of anti-ENA ant ibodies in SLE was increased and clinically useful antibodies such as anti- 52kDa SS-A and anti-PCNA could be detected.