Comparison of a multiplex, bead-based fluorescent assay and immunofluorescence methods for the detection of ANA and ANCA autoantibodies in human serum.

Detection of antinuclear (ANA) and antineutrophil cytoplasmic (ANCA) antibodies is extensively used for establishing a diagnosis in patients with clinical features suggestive of autoimmune disorders. The most common methods for the identification of positive patients' sera for ANA or ANCA are indirect immunofluorescence (IIF) and ELISA-based procedures. Considerable effort has been made in developing simpler automated assays for routine laboratory use. Recently a commercially available microsphere-based fluorescent assay has been introduced for the detection of ANA and ANCA. The aim of this study was to compare this technology with routinely used IIF and ELISA procedures, in patients with a suggested autoimmune disorder. A highly significant correlation between ELISA procedures for specific antibodies and the microsphere-based assays were obtained for both ANA and ANCA as well as for extractable nuclear antigens ELISA screening, indicating that multiplex technology could replace individual ELISA tests for the measurement of specific autoantibodies. However, a low sensitivity for identifying IIF-positive cases was obtained for both ANA (58.0%) and ANCA (59.1%), although there was a significant correlation between the assays. In conclusion, our data show that a microsphere-based fluorescent assay may be a valid platform for the simultaneous determination of circulating individual ANA and ANCA autoantibodies. Furthermore, multiplexing technology offers several advantages that will probably make it an attractive tool in the future. Nevertheless, until further studies are conducted that determine the clinical performance of the multiplex technology, the initial screening of patients for autoantibodies with IIF is still considered necessary.