Multi-round virus filter integrity test sensitivity.

Virus filtration is becoming increasingly prominent in biopharmaceutical recovery processes as a robust method to remove a broad range of virus types. Increasing batch sizes will require large numbers of individual virus filter elements operating in parallel. Before adopting a more complex strategy for managing the integrity testing of large assemblies of virus filters, it is important to understand the sensitivity of the forward flow diffusion test for a single filter and for multiple filters in a single housing. An approach has been developed to estimate the largest hole that could consistently go undetected in a single filter within a larger assembly of virus filters. The integrity test limited minimum log reduction value (LRV) is determined based on the size of the hole as a function of the number of filters in the housing. This minimum LRV is shown to be largely insensitive to the number of filters within the housing. The likelihood of such damage occurring is expected to be very low. This analysis suggests there is minimal benefit to placing filters in individual housings or to adjusting the test specification to compensate for larger numbers of filters in a given housing.