Standardization of assays of neuraminidase and its antibody

The effect of various factors on the reproducibility of neuraminidase and NI antibody assays has been investigated. These factors include the substrate, strain of virus, nature of virus, i.e. whole, subunit or recombinant, temperature and pH. In assaying antibody levels the challenge virus should be standardized by a method other than optical density. It is recommended that a collaborative study should be set up to establish an international standard for neuraminidase and that this should incorporate a comparison of different methods.