Antisynthetase antibodies reveal a broader clinical spectrum than classic syndrome criteria suggest

Patients testing positive for antisynthetase antibodies (ASAbs) in a large, unselected hospital population show far more varied disease patterns than classic antisynthetase syndrome criteria capture, according to a retrospective cohort study published in BMC Rheumatology. The researchers analysed nearly two decades of laboratory data from Hunter New England Pathology Service in Australia, identifying every patient with a positive ASAb result on line blot immunoassay between 2004 and 2023, regardless of their clinical diagnosis.

Of 1,681 myositis line immunoassays performed, 197 patients had positive ASAbs and formed the cohort. Using Connors’ criteria, 61.4% were diagnosed with antisynthetase syndrome (ASyS), but only 18.3% met Solomon’s criteria and 34% met CLASS criteria for definite ASyS. The authors describe this as substantial diagnostic variability, meaning that whether a patient is labelled as having ASyS depends heavily on which criteria set is applied.

Beyond the classic syndrome, the study documented a wide range of clinical features. Interstitial lung disease (ILD) was present in 32.5% of patients, inflammatory arthritis in 27.4%, and myositis in 25.9%. Nonspecific interstitial pneumonia (NSIP) was the most common ILD pattern overall. Anti-PL-12 antibody positivity was associated with a higher frequency of ILD and with lower mean forced vital capacity (FVC) and diffusing capacity for carbon monoxide (DLco), indicating more impaired lung function in that subgroup.

Notably, even borderline antibody results were still associated with myositis and ILD, suggesting that weaker positives may carry clinical relevance rather than being dismissible artefacts. Five-year mortality in the cohort was 11.7%, and malignancy prevalence was 16.2%, both higher than Australian population estimates.

The authors state that, to their knowledge, this is the largest single-centre cohort defined by ASAb positivity irrespective of clinical diagnosis. ASAbs are associated with significant muscle and lung disease and account for 25–30% of myositis-specific antibodies, but previously published cohorts were largely clinically preselected, introducing recruitment bias. By including every positive result regardless of presentation, this study offers a less filtered view of who carries these antibodies and what disease they develop.

The key finding is that prototypic ASyS features were present in only a minority of antibody-positive patients, with marked discordance across classification criteria. The researchers conclude that these findings demonstrate phenotypic heterogeneity and support further investigation into ASAb pathogenicity and specificity. As a retrospective observational cohort study based on descriptive and comparative analysis of electronic records, it establishes associations within this population rather than causal effects, and the single-centre design may limit generalisability.

Subject of Research: Clinical features and outcomes of antisynthetase antibody positivity in an unselected general hospital cohort

Article Title: Clinical spectrum of antisynthetase antibody positivity in a non-preselected general hospital population

Article References: Kasto, D., McLucas, M., Gardiner, B., Aubin, A.-M., Faigl, A., & Major, G. (2026). Clinical spectrum of antisynthetase antibody positivity in a non-preselected general hospital population. BMC Rheumatology. https://doi.org/10.1186/s41927-026-00705-0

Image Credits: AI Generated

DOI: 10.1186/s41927-026-00705-0

Keywords: antisynthetase antibodies, antisynthetase syndrome, myositis, interstitial lung disease, NSIP, anti-PL-12, line blot immunoassay, diagnostic criteria, retrospective cohort, rheumatology, autoantibodies, mortality