B-166 Analytical Performance of Pictor’s PictHealth™ Immunoscreen ENA Targeted Proteomics Assay Compared with Commercial Platforms

Abstract

Extractable nuclear antigen (ENA) antibody testing is central to the diagnosis of systemic autoimmune rheumatic diseases (SARDs). However, widely used multiplex platforms often require specialized instruments and high operational costs, limiting accessibility in many laboratories. We evaluated the performance of the PictHealth™ Immunoscreen ENA assay, a targeted proteomics platform designed for scalable and cost-effective ENA antibody detection. Serum samples from patients with autoimmune diseases and healthy controls were analyzed using the PictHealth™ Immunoscreen ENA assay detecting eight autoantibodies (RNP/Sm, SSA/Ro60, SSA/Ro52, SSB/La, Jo-1, Scl-70, Sm, and CENP-B). Assay performance was compared with two established commercial platforms: Euroimmun ENA Immunoblot and BioPlex 2200 ENA assays. Cut-off values were determined using receiver operating characteristic (ROC) analysis. Concordance was evaluated using three-way agreement as well as pairwise positive percent agreement (PPA) and negative percent agreement (NPA). Analytical precision was assessed within and between manufacturing lots. ROC analysis demonstrated strong discriminatory performance, with most antigens achieving area under the curve values greater than 0.80. Agreement with the Euroimmun comparator showed high performance, with PPA ranging from 91% to 100% and NPA from 87% to 100% across most antigens. Three-way concordance among the PictHealth™, Euroimmun, and BioPlex assays ranged from 67.3% for SSA/Ro52 to 100% for Jo-1, with high concordance observed for Sm and CENP-B (95%). Pairwise comparisons demonstrated PPA and NPA exceeding 85% for most antibodies. Precision studies showed strong reproducibility, with intra-lot coefficients of variation generally below 15% for high- and medium-reactivity samples. The PictHealth™ Immunoscreen ENA assay demonstrates diagnostic performance comparable to established multiplex platforms while maintaining the simplicity and scalability of a conventional ELISA workflow. This approach can be expanded access to reliable ENA antibody testing in laboratories with diverse resource levels and support broader implementation of autoimmune diagnostics.