OOS – Out of Specification Results

The purpose of such OOS SOP (Standard Operation Procedure) is to establish and describe the principle steps involved for the handling of out-of-specification (OOS) laboratory results. The investigation or ‘failure investigation’ should identify the cause or root cause of the OOS and evaluate its impact on the tested product.


The FDA Guideline “Investigating Out of Specification (OOS) Test Results for Pharmaceutical Production” needs to be considered.

The OOS SOP procedure should be applicable to all GMP testing laboratories testing e.g. excipients, raw materials, water analysis, utilities, environmental conditions, packaging materials and components, drug substance, finished drug product, device components, finished devices and any stability samples.