POS0789 APPLICATION OF THE NEW ACR/EULAR 2019 CLASSIFICATION CRITERIA OF SYSTEMIC LUPUS ERYTHEMATOSUS TO A INCEPTION, MONOCENTRIC COHORT OF UNDIFFERENTIATED CONNECTIVE TISSUE DISEASES POPULATION AT ONSET OF THE DISEASE

Background:undifferentiated connective tissue diseases (UCTDs) are a group of systemic autoimmune diseases that share clinical and serological manifestations with definite connective tissue diseases (CTDs), but do not satisfy existing classification criteria1. Within this group, it is possible to identify very heterogeneous conditions: transitory and self-limiting forms, stable conditions over time and forms that will evolve towards definite CTDs, in particular Systemic Lupus Erythematosus (SLE). The availability of new classification criteria for CTDs could be useful in identifying major CTDs from their onset and help in the differentiation from stable UCTDs, which will maintain their undifferentiated profile over time.Objectives:the aim of this study was to apply the new ACR/EULAR 2019 classification criteria of SLE2 to patients included, at the onset of UCTD, to evaluate how many patients could be re-classified as SLE.Methods:this is a retrospective observational study that enrolls patients who received the diagnosis of UCTD at the Rheumatology Unit of Pisa, according to the classification criteria proposed by Mosca et al1, and were then regularly followed in the same clinic (inception cohort). For each patient, demographics, comorbidities, treatment, clinical and serological data were collected, at baseline and during follow-up. The new ACR/EULAR 2019 classification criteria of SLE were applied to the inception cohort at the onset of the disease. The characteristics of patients re-classified as SLE according to the new classification criteria and those of patients who “remained” classified as UCTD were compared.Results:we enrolled 202 patients with a diagnosis of UCTD, mainly female (F:M 193:9) and of Caucasian ethnicity (97.5%), mean age at the diagnosis 38,5 ± 13,2 years and a median follow-up of 5 years (IQR 2-10).During the follow-up, 10 patients (4.9%) in our cohort developed clinical and serological characteristics that led to a diagnosis of a definite CTD, in particular: 7 SLE, 2 Mixed Connective Tissue Disease (MCTD) and 1 Sjogren’s syndrome.Applying the ACR/EULAR 2019 classification criteria of SLE to patients enrolled at the onset of the disease, 38/202 (18.8%) would have been classified as SLE (with a median score of 12 (IQR 11-15)) on the basis of the presenting clinical and serological manifestations. Interestingly, 6/7 patients who received a diagnosis of SLE during the follow-up were among these 38 patients.Among the items of the new classification criteria of SLE, the most frequently satisfied by patients “re-classified” were arthritis (63.2%), hematological (44.7%) and skin (23.7%) manifestations; as for the “immunological” items, hypocomplementemia (71%), SLE-specific (52.6%) and antiphospholipid (35.1%) autoantibodies.Comparing the subgroup of patients “re-classified” as SLE with that of patients who “remained” UCTD, we found that the first group presented more frequently hematological manifestations, hypocomplementemia and anti-dsDNA, anti-Sm, anti-RNP, anti-beta2GPI positivity at the onset of the disease (p<0.01). Moreover, during the follow-up, the subgroup of patients “re-classified” as SLE developed more frequently malar (p<0.05) and discoid rash and arthritis (p<0.01) compared to patients who “remained” UCTD.Conclusion:The development of increasingly sensible and specific classification criteria for definite CTDs may guide in the identification of stable UCTDs since their early stages and consequently in better definition of these conditions that can be considered as a distinct clinical entity.The early identification of stable UCTD is of great importance not only for clinical management (follow-up schedules as well as therapeutic protocols) but also for scientific implications.References:[1]Mosca M. et al., Clin Exp Rheumatol. Sep-Oct 1999;17(5):615-20; 2. Fanouriakis A. et al., Ann Rheum Dis. 2020 Jun;79(6):713-723.Disclosure of Interests:None declared

Anti-TIF-1γ Antibody Detection Using a Commercial Kit vs In-House Immunoblot: Usefulness in Clinical Practice

ObjectivesAnti-TIF-1γ autoantibody detection is important for cancer screening in patients with dermatomyositis. The gold standard for anti-TIF-1γ detection, immunoprecipitation, is only available from a few specialized laboratories worldwide, so commercial ELISA/immunoblot tests have emerged in recent years. To analyze their usefulness in diagnosing cancer-associated dermatomyositis, we compared Euroimmun Euroline profile with our previously validated in-house immunoblot assay with human recombinant TIF-1γ.MethodsWe included 308 adult patients from Hospital de la Santa Creu I Sant Pau and Vall Hebrón Hospital (Barcelona, Spain) tested for anti-TIF-1γ autoantibodies using the Euroline profile and an in-house immunoblot assay.ResultsA total of 27 anti-TIF-1γ were detected by the Euroline and 12 by the in-house assay. Fair agreement was observed between Euroline and the in-house immunoblot Cohen’s kappa 0.3163. Expected prevalence of anti-TIF-1γ autoantibodies was observed for the two methods for dermatomyositis and undifferentiated connective tissue diseases, but unexpectedly high prevalence of anti-TIF-1γ autoantibodies was detected by Euroline compared to the in-house immunoblot for other diseases (16.5% Euroline vs 0.8% in-house immunoblot, p&lt;0.01). The in-house IB compared to Euroline more reliably detected cancer in patients with DM with anti-TIF-1γ antibodies (p=0.0014 vs p=0.0502 for in-house immunoblot vs Euroline).ConclusionWe recommend using a second validated method to confirm Euroline-detected anti-TIF-1γ antibodies when the dermatomyositis diagnosis is not definitive. Furthermore, in the context of definite DM diagnosis with negative anti-TIF-1γ antibodies by Euroline and no other myositis specific antibody, is also recommendable to confirm by a second validated method.

Clinical associations of the positive anti Ro52 without Ro60 autoantibodies: undifferentiated connective tissue diseases

AimsAutoantibodies targeting Ro52 and Ro60 antigens are historically reported as anti SSA/Ro. In general anti SSA/Ro results are either anti Ro52+Ro60+ or anti Ro52−Ro60+ antibodies. Anti Ro52 without anti Ro60 (Ro52+ Ro60−) antibodies are often not reported routinely. This study intends to review the potential significance of these autoantibodies in the management of connective tissue diseases.MethodA retrospective survey of Ro52+Ro60− was carried out as part of the service evaluation of extractable nuclear antigen antibodies (ENA) reporting from the immunology laboratory, the NHS Greater Glasgow and Clyde (GGC), UK. The clinical documents and laboratory results of 97 patients with Ro52+Ro60− and 100 patients with Ro52+Ro60+ were reviewed.ResultsSeventy-one patients (73%) with anti Ro52+Ro60− antibodies have been diagnosed with autoimmune conditions including undifferentiated connective tissue diseases (n=14, 14%), systemic lupus erythematosus (n=10, 10%), Sjögren’s syndrome (n=10, 10%) and rheumatoid arthritis (n=13, 13%). Twenty-three patients (24%) with anti Ro52+Ro60− antibodies have no autoimmune features but were found to have significant clinical conditions including malignancies. In contrast, 87 patients (87%) with anti Ro52+Ro60+ antibodies have autoimmune conditions including Sjögren’s syndrome (n=34, 34%), systemic lupus erythematosus (SLE; n=23, 23%), undifferentiated connective tissue diseases (n=12, 12%) and rheumatoid arthritis (n=6, 6%).ConclusionAnti Ro52 without anti Ro60 (Ro52+Ro60−) antibodies should be reported. In the majority of patients these autoantibodies were associated with various autoimmune diseases. Anti Ro52+Ro60− antibodies were also found in patients with significant clinical conditions including malignancies even though there was no suggestion of autoimmunity at the time of testing.