Detection of Autoantibodies for Extractable Nuclear Antigens by LG Immunoblot Kit

Background : Identification of antibodies recognizing extractable nuclear antigens (ENAs) is useful in the diagnosis and characterization of a variety of connective tissue diseases. Recently, LG ENA Immunoblot (LGCI, Korea) was introduced for detecting various autoantibodies to ENAs simultaneously. Performance of this kit was evaluated in this study. Methods : Sera from 108 SLE patients and 103 RA patients were tested for the presence of specific autoantibodies to ENAs by LG ENA Immunoblot and DID. Concordance rates in each autoantibody were obtained. After discordant results were resolved by EIA (ENA ELISA TEST SYSTEM, Zeus Scientific Inc., NJ, USA) and western blot (ANA Western Blot Immunoassay, IMMCO Diagnostics Inc., NY, USA), sensitivity and specificity of LG ENA Immunoblot were evaluated. Betweenday precision was also tested. Results : Concordance rates in each autoantibody in two methods were as follows: anti-RNP (88.0%, 95/108; 100.0%, 103/103), anti-Sm (87.0%, 94/108; 97.1%, 100/103), anti-SSA (94.4%, 102/108; 99.0%, 102/103), anti-SSB (97.2%, 105/108; 98.1%, 101/103), anti-Scl70 (99.1%, 107/108; 100.0%, 103/103) in SLE and RA patients, respectively. Sensitivity and specificity of Immunoblot were 92.0% and 99.6% for anti-RNP, 100.0% and 99.6% for anti-Sm, 100% and 98.6% for anti-SSA, 90.0% and 98.5% for anti-SSB, and 100.0% and 100.0% for anti-Scl70, respectively. Between-day precisions were 100% in all anti-ENA antibodies. Conclusions : LG ENA Immunoblot showed good concordance rates with the conventional DID method and high sensitivity (>90%) and specificity (>98.5%) in detecting all kinds of anti-ENA autoantibodies. LG Immunoblot has another merit in that it can detect several autoantibodies simultaneously. It is suggested that LG ENA Immunoblot can replace DID for anti-ENA detection without any problem.