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Introduction: The most common extramuscular manifestation of the idiopathic inflammatory myopathies (IIM) is interstitial lung disease (ILD) and the diagnosis is based on serum autoantibodies. The new specific and associated antibodies to IIM have helped to identify new clinical entities in the spectrum of IIM. The objective of this study is to evaluate the diagnostic contribution of a myositis antibodies panel (MP) in a cohort of Chilean patients with ILD without a definitive connective tissue disease (CTD). Materials and Methods: Starting on January 2017 we performed a MP to 111 consecutive patients with ILD and suspected CTD but without a definitive diagnosis through another diagnostic tools in the Lung-Rheumatological Program at the “Instituto Nacional del Torax”, Santiago, Chile. The clinical and serological baseline characteristics of the patients that were most frequently associated with the probability of having a positive panel were compared. Results: The MP was positive in 56 of 111 patients. Anti synthetase syndrome (ASS) was the most prevalent diagnosis. The most frequent antibodies were Ro-52, PM/Scl-75 and Ku. The most frequent variables in the positive MP group were the presence of Raynaud’s phenomenon, myositis, mechanic’s hands, positive Ro and La antibodies and the presence of combined pattern of nonspecific interstitial pneumonia and organizing pneumonia in chest computed tomography scan. Conclusions: The incorporation of the MP has helped us to improve our diagnostic precision of patients with CTD/ILD. We present clinical and serological elements that refine the performance of the test.

Prior to the publication of the 2002 ATS / ERS classification of idiopathic interstitial pneumonias (IIP), the histopathological evaluation was considered the gold standard for the diagnosis of interstitial lung diseases (ILD). However, several subsequent studies showed that interobserver concordances between expert lung pathologists were surprisingly poor, since histopathological appearances may overlap between different entities. Therefore, a new diagnostic system that serves as a gold standard in patients with ILD became necessary. This is how the concept of multidisciplinary discussion was born, to refer to a meeting that allows the integration of all the clinical, radiological and pathological data available for an individual patient and thus be able to determine a working diagnosis.