The purpose of this study is to compare newly developed assay for identification of ENA antibody, Phadia EliA ENA with Euroimmun line immunoassay by analyzing the degree of agreement and the individual antibodies between two methods.

A total of 82 patient samples were used. Indirect immunofluorescence assay using Hep-2 cell was performed to screen the antinuclear antibody (ANA). Euroimmun line immunoassay (LIA) and Phadia EliA ENA assay were tested to identify the antibodies against extractable nuclear antigens (ENAs). Kappa statistics was used to evaluate the degree of agreement.

Mean age of patients was 41.0 (8-79), and the M:F ratio was 21:61. ANA was positive in 74 samples, and negative were 8 samples. Kappa analysis of the 82 tested samples showed a moderate strength of agreement (κ = 0.521, P = 0.000). There were differences in the order of identified individual antibodies between two methods (Ro > La = RNP > Centromere > Sm > Scl-70 in Phadia EliA ENA, Ro > RNP > Sm>La > Scl-70 > Centromere=Jo-1 in Euroimmun LIA). Ro antibody was most frequently identified in Phadia EliA ENA negative-Euroimmun LIA positive specimens (Ro > RNP = Jo-1 > La = Sm = Centromere > Scl-70).

A moderate strength of agreement was observed between the Phadia EliA ENA and the Euroimmun LIA. There seemed to be a significant difference in the ratio of individual antibodies, especially in the anti-Ro and Sm antibodies.