[The unitage assigned by the WHO to International biological Standards - substances, classed as biological according to the criteria provided by WHO Expert Committee on Biological Standardization (e.g. hormones, enzymes, and vaccines), to enable the results of biological and immunological assay procedures to be expressed in the same way throughout the world. The definition of an international unit is generally arbitrary and technical, and has to be officially approved by the International Conference for Unification of Formulae. ( NCI )] (UMLS (NCI) C0439453) =Quantitative Concept =UnitOfMeasureAtomInsens; UnitOfMeasureAtomSens