International standard reference serum. Certain laboratories prepare reference serum to a very high standard. Standard reference Anti-Newcastle disease serum is available for purchase. It is used as a reference serum in the preparation of national and laboratory standard sera.
The National Institute for Biological Standards and Control (NIBSC) in the United Kingdom can supply an international standard reference serum. The potency of the international reference serum has been determined by the supplier and is expressed in International Units (IU) per ampoule of freeze-dried serum.