Diagnostic performance of Pictor's targeted proteomics assay for extractable nuclear antigens compared with commercial line immunoassay and addressable laser bead immunoassay platforms.
Extractable nuclear antigen (ENA) antibody testing is universal to the diagnosis of systemic autoimmune rheumatic diseases (SARDs). However, current commercial multiplex platforms require expensive instruments and are often cost-prohibitive for routine testing in low- and middle-income settings. Pictor PictHealth® Immunoscreen ENA assay was developed as an affordable, scalable alternative for the simultaneous detection of ENA antibodies. The assay performance was compared with the Euroimmun ENA Line immunoassay and BioPlex 2200 ENA assays using clinical sera from patients with autoimmune diseases. Concordance among assays was evaluated using three-way and pairwise analyses, expressed as positive percent agreement (PPA), negative percent agreement (NPA), and overall concordance. Analytical precision was assessed within and between manufacturing lots. The Pictor multiplex assay showed high concordance with established commercial platforms. Three-way agreement across all assays ranged from 67.3% for TRIM21/Ro52 to 100% for Jo-1, with Sm, CENP-B showing concordance of 95%. Pairwise comparisons demonstrated PPA and NPA values exceeding 85% for most autoantibodies. The Pictor PictHealth® Immunoscreen ENA assay provides diagnostic performance comparable to the Euroimmun and BioPlex platforms while maintaining the ease of implementation and scalability of a traditional ELISA format. These results support its potential as a cost-effective and accessible tool for ENA antibody testing in laboratories with varying resource levels.