Out-of-trend (OOT) result

A result that is still within specification but departs from the expected trend, for example an impurity in a stability study rising faster than in earlier lots. Japanese documents often just write OOT. Trends are the early signal before an OOS. PMDA treats ignored trends as a GMP problem. Its ORANGE Letter of July 2023 described a drug substance lot whose related substance approached the upper limit at 48 months, still within specification, with no investigation or risk assessment; PMDA asked for procedures that evaluate signs of abnormal trends. A January 2026 letter covered unfavorable trends left without action. Expect a Japanese customer to ask how your procedures define and escalate OOT.