Measurement of parainfluenza-3 virus antibody by the single radial hemolysis technique.

A single radial hemolysis assay for parainfluenza-3 virus antibody is described as a simple, sensitive, accurate, and precise alternative to hemagglutination inhibition and serum neutralization tests. A highly significant correlation exists between single radial hemolysis zone areas and hemagglutination inhibition titers of both serum and nasal secretion samples. Antibody conversions equivalent to as little as a twofold rise in hemagglutination inhibition titer are readily and reliably detected in sera and nasal secretions. Single radial hemolysis and hemagglutination inhibition activity was demonstrable in the immunoglobulin G fraction of a hyperimmune parainfluenza-3 virus antiserum.