PT - JOURNAL ARTICLE AU - Jens Lamerz AU - Oana Mihaela Danila AU - Andreas Schuster AU - Janine Burren AU - Christian Moessner AU - Wolfgang Göhring AU - Pankaj Rege AU - Helmut Stahr AU - Stefan Hildbrand AU - Daniel Coleman TI - An Improved Impact Ratio for Identifying Critical Process Parameters in Pharmaceutical Manufacturing Processes AID - 10.5731/pdajpst.2021.012662 DP - 2022 Nov 01 TA - PDA Journal of Pharmaceutical Science and Technology PG - 497--508 VI - 76 IP - 6 4099 - http://journal.pda.org/content/76/6/497.short 4100 - http://journal.pda.org/content/76/6/497.full SO - PDA J Pharm Sci Technol2022 Nov 01; 76 AB - The identification of critical process parameters in biologics and small molecule process development is a key element of quality by design. The objectivity and consistency of procedures to identify critical process parameters can be improved with the use of impact ratios. Impact ratios quantify a process parameter’s practical effect on a critical quality attribute relative to the critical quality attribute’s acceptance limits. If the impact ratio is large, i.e., exceeds a predefined impact ratio threshold, the recommendation is to classify the process parameter as a critical process parameter. This article introduces an improved and mathematically well-defined impact ratio. Benefits of this impact ratio are a consistent interpretation for many scenarios commonly encountered in practice, high suitability to automation, and the possibility of standardizing on a single impact ratio definition for pharmaceutical manufacturing.