Macaque liver substrate for evaluating dense fine speckled-like patterns on HEp2010 cells

Antinuclear antibody (ANA) detection by indirect immunofluorescence (IIF) is instrumental in the evaluation of systemic autoimmune diseases (SADs). The dense fine speckled (DFS) ANA staining predominantly associates with anti-DFS70, an autoantibody that is thought to exclude the presence of SAD. However, the DFS pattern may mask the presence of other ANA patterns that may be clinically relevant. Our laboratory uses the HEp2010 substrate which contains both HEp2 and liver substates. The aim of this study was to determine whether negative liver nucleus immunofluorescence could exclude the presence of antibodies to extractable nuclear antigens (ENA) in sera with DFS-like patterns. One hundred consecutive sera samples suspicious for DFS pattern, along with 15 sera of control patterns (positive metaphase bars) were included in the study. Each sample was examined separately on HEp2010 (Euroimmun) and liver by two independent readers. Anti-DFS70 was assessed by line and chemiluminescent immunoassays. DFS-like sera were more likely to be liver nucleus-negative compared with control sera. Of the liver-negative sera, 61/64 (95.3%) were deemed anti-ENA negative. Using the liver substrate in the evaluation of anti-ENA had a sensitivity of 90.0% and a negative predictive value of 95.4%. In our cohort, concurrent evaluation of sera with the liver substrate helped rule out the presence of other anti-ENA. This technique may be a safeguard for DFS-like ANA patterns that may mask underlying anti-ENA on IIF.