Out-of-specification (OOS) refers to any analytical result or test observation that falls outside the predetermined acceptance criteria or specifications established for a drug substance, drug product, raw material, or in-process sample during pharmaceutical or biopharmaceutical manufacturing. OOS results must be formally investigated following a documented investigation procedure that includes laboratory investigation, manufacturing review, and, where necessary, corrective and preventive actions (CAPA). The handling of OOS results is subject to strict GMP guidelines and regulatory expectations from agencies such as the FDA and EMA, and directly impacts batch release decisions and product quality outcomes.
