The<unk>  (or<unk> ;<unk>  is a method of quantification for viruses or bacteria by<unk> . It is an easy, simple and rapid method which can be applied to large numbers of samples. The<unk>  and its extension, the<unk>  inhibition assay, were invented in 1941–42 by American virologist George Hirst.
The<unk>  of a virus, in contrast to other forms of virus quantification such as a plaque assay or 50% Tissue Culture Infective Dose, does not give any measure of viral infectivity, because no virus replication is required in this assay. The same may not be true when using<unk>  for bacteria.
Hemagglutination assay
Plaque reduction neutralization test
Direct fluorescent antibody
Heterophile antibody test
Nucleic acid hybridization
Nucleic acid test
Enzyme assay
Counterimmunoelectrophoresis