Appropriate tests need to be performed in order to determine if the cell bank is what it is represented to be. Either phenotypic or genotypic characteristics may be used in identity testing. Tests of identity are generally performed on the MCB. In addition, limited identity testing is generally performed on each WCB.

For the microbial cells, analysis of growth on selective media is usually adequate to confirm host cell identity at the species level for the host cell bank and the transformed cell bank.

• For bacterial cell bank, where a variety of strains may be used, biological characterization methods such as phage typing should be considered as supplementary tests of identity.
• For expression system and plasmid banks, identity assessment can be accomplished as described by the ICH document on analysis of the expression construct. Expression of the desired product is also considered adequate to confirm the identity of the microbial expression system.