Anti-synthetase syndrome (ASyS) is an autoimmune disorder with clinical manifestations that often include interstitial lung disease (ILD), myositis, and arthritis. Although it shares features with other idiopathic inflammatory myopathies, ILD is more prevalent and often more severe in this syndrome. The aim of this study was to compare Connors and Solomon diagnostic criteria for ASyS and investigated whether the presence of no additional symptoms, one additional symptom, or two or more symptoms, in addition to ILD and relevant antibodies, would indicate a worse prognosis.

This retrospective single-center study examined patients who were previously diagnosed with ASyS based on Connors or Solomon criteria and were further categorized using the 273rd ENMC International workshop criteria and post-hoc. The patients were then stratified based upon how many “defining” signs and symptoms that they had in addition to ILD and antibodies. Demographic characteristics, pulmonary function tests (PFT), chest CT’s—along with clinical outcomes were assessed.

No differences in demographic factors and PFT’s were found between those who were diagnosed using Solomons versus Connors criteria. No differences in demographic, PFT’s and chest CT’s between those with ILD and antibodies only, with 1 additional criteria, and with 2+ additional criteria groups, although those with two or more additional criteria had a longer duration since diagnosis.

Key findings from the study suggest that there are no differences in diagnostic outcomes, therapeutic interventions, or mortality rates when using different criteria to diagnose ASyS. This study suggests a reevaluation of diagnostic criteria for ASyS to prioritize ILD and relevant antibodies rather than a focus of additional criteria, supporting the new ASyS defining criteria from 273rd ENMC International Workshop (2024).