Out-of-specification (OOS) regulatory issues have been well documented in the literature (1). Out-of-trend (OOT) stability data identification and investigation is rapidly gaining regulatory interest. An OOT result is a stability result that does not follow the expected trend, either in comparison with other stability batches or with respect to previous results collected during a stability study. The result is not necessarily OOS but does not look like a typical data point. This article discusses the regulatory and business basis, possible statistical approaches, and implementation challenges to the identification of OOT stability data. Representatives from PhRMA member companies met to consider these topics, review current practices, and summarize various approaches to potentially address this issue. It is noted that the identification of OOT results is a complicated issue and that further research and discussion is needed. This article is not a detailed proposal but is meant to begin the dialogue toward achieving more clarity about how to address the identification of out-of-trend stability results.

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