What does FDA expect from an OOS investigation beyond the initial laboratory assessment?

An initial laboratory assessment should determine whether a credible, documented laboratory cause exists, but it should not become a mechanism for stopping the investigation prematurely. When no assignable laboratory cause is established, the investigation should expand to manufacturing, sampling, materials, methods, equipment, related results, and potential batch or product impact. The organization should preserve the original result, avoid testing into compliance, document the rationale for every conclusion, and connect findings to CAPA and effectiveness verification.