Concentrations of plasma immunoglobulins in the dog as determined by laser nephelometry. Comparison with radial immunodiffusion and enzyme-linked immunosorbent assay

Concentrations of immunoglobulins were determined by laser nephelometry and, for comparison, by single radial immunodiffusion assay and a sandwich enzyme-linked immunosorbent assay (ELISA) in plasma samples of normal dogs. Correlation between methods was high, although the mean IgM concentrations determined by laser nephelometry were significantly higher than those determined by the single radial immunodiffusion assay or ELISA. In contrast, the mean IgA concentrations were significantly lower than those determined by ELISA. Laser nephelometry was the most reproducible method. The between-assay coefficient of variation was 4.12% for IgG, 6.98% for IgM and 6.35% for IgA. Laser nephelometry and ELISA showed similar accuracies, and both were more accurate than single radial immunodiffusion. Finally, laser nephelometry was much more sensitive than single radial immunodiffusion, but less sensitive than the ELISA method. In conclusion, results of the three methods were in general comparable. The higher range of linearity, precision and accuracy of laser nephelometry, and the availability of automated nephelometers make this the method of choice for quantifying canine plasma immunoglobulins.