Quantities and units for biological reference materials used with in vitro diagnostic measuring systems for...

The WHO International Reference Materials (IRM), whether International Biological Standards (IS) (formerly International Reference Preparations (IRP)) or International Biological Reference Reagents (IRR), have served a good purpose in standardizing bioprocedures by defining international units of bioactivity or potency where dimensions seem difficult to establish. Especially for in vitro diagnostic procedures, the trend is towards measuring biochemically informative molecular-based quantities (involving the unit mole) when some chemical entity of a component can be defined. The use of a standard, with a value assigned by any procedure, as a calibrant in other procedures does not assure traceability and valid diagnostic results if the component (analyte) is microheterogeneous to a varying degree or there are varying matrix effects. Only experiment can demonstrate commutability of the material.