Background ANA are a large family of autoantibodies directed at various cellular constituents. The measurement of ANA is a useful tool to confirm the diagnosis of SLE. New automated bead-based arrays can simultaneously and rapidly determine a profile of multiple ANA. Clinical performance of multiplexed technologies for detection of ANA specificities in SLE is not validated.
Objectives To evaluate the diagnostic accuracy of multiplex bead-based immunoassay for the detection of ANA profile in SLE.
Methods We studied 94 patients (pts) (80 F, age 35.9 [16.0–65.0] years, disease duration 113.5 [2.0–576.0] months) with SLE (ACR criteria, 1997), 50 pts with other systemic autoimmune rheumatic diseases, 20 pts with non-autoimmune rheumatic diseases and 30 healthy controls. Serum samples were analyzed for SLE-associated ANA (anti-dsDNA, anti-Sm, anti-chromatin, anti-SS-A/Ro 52 kDa and 60 kDa, anti-SS-B/La, anti-RNP-70, anti-ribosomal P) using automated multiplex bead-based immunoassay system BioPlex® 2200 (ANA Screen; Bio-Rad Laboratories Inc., USA). The following ANA values were considered positive: anti-dsDNA≥10.0 IU/mL, other antigen-specific ANA ≥1.0 AI (Antibody Index).
Results The detection of anti-dsDNA, anti-Sm, anti-ribosomal P antibodies by BioPlex assay demonstrated the highest overall specificity (0.95, 0.97, 0.99, respectively), and positive likelihood ratio (LR) (10.40, 9.67, 15.0, respectively) for diagnosis of SLE (Table 1). BioPlex assay for anti-RNP-70, anti-SS-A/Ro, anti-chromatin antibodies was a useful diagnostic test in SLE (positive LR 2.80, 2.31, 4.15, respectively). Anti-SS-B/La antibodies testing had no value in SLE diagnosis (positive LR 1.20). The frequency of 1 ANA in SLE pts was 79.8%,2 ANA – 28.7%, 3 ANA – 15.6%, 4 ANA – 10.6%, 5 ANA – 5.3%, 6 ANA – 1.1%. Simultaneous detection of ≥3 ANA increased the specificity of multiplex immunoassay up to 0.98–1.00, and positive LR – to a maximum value.
Conclusions The detection of ANA profile by multiplex bead-based immunoassay has a high specificity and positive likelihood ratio for diagnosis of SLE. Additional investigations are required to evaluate the usefulness of multiplex ANA testing for monitoring disease activity and for determining prognosis of SLE.
Disclosure of Interest None declared
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