Evaluation of a microsphere-based immunofluorescence assay for the determination of Immunoglobulin A concentrations in cerebrospinal fluid of dogs

The simultaneous increase of immunoglobulin A (IgA) in serum and cerebrospinal fluid (CSF) is a characteristic finding in dogs suffering from canine steroid-responsive meningitis–arteritis (SRMA). The study aimed at developing and evaluating a microsphere-based immunofluorescence assay (MIA) for the measurement of IgA, trying to fulfill the need of a quicker method using only small volumes of CSF.Microsphere beads were coated with goat-anti-dog IgA antibodies and bound IgA was detected by a mouse-anti-dog IgA antibody in combination with a PE-labeled goat-anti-mouse IgG. CSF from 44 dogs were tested for IgA and compared with an in-house utilized ELISA.Using clinical relevant reference ranges, the new method showed a good agreement (84.17%) with the ELISA. A method comparison revealed a moderate agreement only. These findings indicate that the MIA will not replace the ELISA, but it opens the possibility for further research with microsphere-based assays.