Tu121 - Clinical Utility of Extractable Nuclear Antigens (ENA) Testing in Autoimmune Diseases: A One-year Analysis

Abstract Text: We analyzed ENA results from 261 patients over a one-year period, comparing ANA results and clinical diagnoses to assess the utility of ENA testing. ENA was performed using EUROBlotOne(EUROIMMUN, Germany), and ANA with QUANTA-Lyser®2(Werfen, USA). Ro-52(23.4%) and SS-A(18.0%) showed the highest positivity rates, with speckled ANA patterns being the most common. Although SS-B antibodies were detected in only 4.6% of patients, all showed ANA titers of ≥1:320 with speckled pattern. SLE-specific antibodies, dsDNA and Sm, had 6.1%(16 patients) and 3.1%(8 patients) positivity. All Sm-positive patients exhibited SLE-associated symptoms, while 9 dsDNA-positive patients showed no SLE-associated symptoms, and 3 had low ANA titers. Nucleosome positivity(5.4%) was associated with SLE symptoms in 71% of cases. Homogeneous ANA patterns were predominant(78.6%), though rare patterns like PCNA were observed. The patient with the PCNA pattern also showed positive for PCNA in the ENA. Centromere B positivity(5.0%) correlated with SSc in 38.5% of cases, with high titers and characteristic ANA patterns. In contrast, Scl-70(1.5%) and PM-Scl(2.7%) positivity showed no association with SSc. RNP antibodies(10%) were associated to MCTD, with most cases showing high ANA titers (≥1:2560) and symptoms of rheumatic diseases. AMA positivity(5.0%) inconsistently correlated with primary biliary cholangitis, as 46.1% showed AMA ANA patterns, but only 2 patients were diagnosed with PBC. Among 35 patients with nonspecific symptoms such as cytopenia, myalgia, and FUO, ENA was negative in 51.4%, and 42.9% had negative ANA results or ANA titers of 1:40. Combining ENA results with ANA patterns and clinical context can support early patient management.