SAT0279 ANTI-RO52 KDA and ANTI-RO60 KDA analysis in systemic lupus erythematous patients to detect ANTI-RO false-negatives
Authors: E Grau Garcia, I Chalmeta Verdejo, E Sánchez Labrador, M Fernandez Matilla, FM Ortiz-Sanjuan, CM Feced Olmos, N Fernandez-Llanio, K Arévalo Ruales, R Negueroles Albuixech, J Ivorra Cortes, JJ Fragio Gil, I Martínez Cordellat, R Mazarío González, L Gonzalez Puig, C Alcañiz Escandell, C Nájera Herranz, I Cánovas Olmos, E Vicens Bernabeu, JE Oller Rodriguez, JA Castellano Cuesta, V Fornés Ferrer, D Marín Hervás, D Gimenez Romero, JA Román Ivorra
Journal: Annals of the Rheumatic Diseases (2017)

<h3>Background</h3> Systemic lupus erythematous (SLE) is an autoimmune disease characterized by immune system disruption with autoantibodies production. One of the upregulated autoantibodies is the specific to the Ro antigen, a ribonucleoprotein associated to a small RNA, constituted by the 52KDa and 60 KDa polypeptides, whose epitopes are mainly conformational. The routine detection method for anti-Ro is an enzyme immunoassay, however, is possible to obtain false-negatives for anti-Ro and this could be avoided by analyzing both subunits separately. <h3>Objectives</h3> To identify false-negatives for anti-Ro by analyzing both 52KDa and 60 KDa subunits separately, as well as to characterize if there are clinical or molecular differences in this subgroup of patients compared to anti-Ro negative cases. <h3>Methods</h3> A cross-sectional, observational study of patients diagnosed of SLE according to SLICC 2012 criteria was performed. In these patients a complete blood-test was made, and clinical data by personal interview was collected. INF1A, Anti-Ro, anti-Ro52KDa and anti-Ro60KDa levels where measured by colorimetric methods. Biostatistical analysis was performed with R 3.3.2. <h3>Results</h3> We selected 69 SLE patients with negative results for anti-Ro (2.34±4.17 U/mL) out of 142 total SLE patients. A total of 51 patients were negative for both anti-Ro subunits and 18 cases presented positive results (up to 20 pg/mL) for at least one of them. The subgroup of patients that exhibit simultaneously high levels of anti-Ro52KDa and anti-Ro60KDa have higher clinical activity compared to negative anti-Ro cases (75% of active patients against 41.2% in anti-Ro negative patients). However, no differences in the accumulated damage evaluated by SLICC score between negative anti-Ro cases and patients with at least one positive subunit were observed. We analyze serum levels of INF1A cytokine in the four groups of patients, and anti-Ro and subunits negative cases showed significant lower INF1A levels than the other patients (8.26±14.87 pg/mL and 26.62±40.71 pg/mL respectively; P=0.04). In addition, patients with high levels of anti-Ro52KDa subunit are those with the highest INF1A levels (anti-Ro 52+/anti-Ro60- 23.5±47.6pg/mL of INF1A; anti-Ro 52+/anti-Ro60+ 36.4±37.9pg/mL of INF1A). <h3>Conclusions</h3> In our anti-Ro seronegative patients, a 26% of false-negative cases were detected. These cases with high levels of almost one anti-Ro subunit showed significantly higher levels of INF1A in contrast to negative cases, supporting the fact that they are indeed a different group from the negative cases. Moreover, the high INF1A levels could be the reason of the observed differences in the clinical activity measured by SLEDAI score in both groups. <h3>Disclosure of Interest</h3> None declared