OOS (out of specification)

A test result that falls outside an established specification for a product or material. In microbiology, examples include a TAMC above the limit, the presence of a specified organism, a positive sterility test or an endotoxin result above the limit. An OOS triggers a phased investigation: first a laboratory investigation, then a full investigation of manufacturing if no clear lab error is found. A result can only be invalidated with documented evidence.