Diagnostic performance of particle-based multi-analyte technology compared to indirect immunofluorescence in screening for anti-nuclear antibodies in patients with autoimmune rheumatic diseases

Objectives: In autoimmune rheumatic disease (ARD), ANA testing is crucial for orienting clinical diagnosis and further diagnostic workups. We evaluated the performance of a fully automated system using particle-based multi-analyte technology (PMAT) and compared it to indirect immunofluorescence (IIF) on HEp-2 cells. Methods: Serum samples from 1241 subjects were collected in 13 Italian rheumatology centres. The ARD group (782 samples) included 164 patients affected by systemic lupus erythematosus, 277 by Sjögren's syndrome, 132 by systemic sclerosis, 106 by idiopathic inflammatory myopathy, and 103 by undifferentiated connective tissue disease. The control group comprised 120 healthy donors, 221 patients affected by other autoimmune/inflammatory disorders, and 118 patients affected by acute or chronic infections. Results: In the overall ARD population, HEp-2 IIF showed higher sensitivity when compared to Aptiva/PMAT (92.8 vs. 82.6%) except in the case of idiopathic inflammatory myopathy (58.5% vs. 82.1%). Conversely, Aptiva/PMAT showed higher specificity (77.9% vs. 54.0%) and a higher likelihood ratio for positive results (3.81 vs. 2.08). Double-positive samples provided an LR for positive results higher than one method alone (6.31). Conclusions: This is the first study comparing Aptiva/PMAT against HEp-2 IIF in ANA detection. While the diagnostic sensitivity of this novel method is lower than that of HEp-2 IIF, its high specificity is a valuable tool in the diagnosis of patients affected by ARD and improves their stratification into specific disease subsets. The combined use of HEp-2 IIF and Aptiva/PMAT assays increases diagnostic accuracy and significantly enhances the potential to accurately classify patients affected by ARDs.