What evidence would justify extending a CAPA to another site or product family?

Why

A CAPA fixes a mechanism, not just a location. If the mechanism exists elsewhere, the same failure is waiting there. ICH Q10 says CAPA should consider other products that might be impacted, and its knowledge management enabler exists so that what one site learns reaches the others.

US regulation already requires investigations to extend to other products that may be associated with a failure. The evidence question is whether the mechanism is present. Suppose a filling line had particle complaints traced to a specific stopper bowl design that abrades stoppers.

Other sites with the same bowl model and the same stopper type share the mechanism, even if they have no complaints yet, because detection may lag. Sites with a different bowl do not. Useful evidence includes equipment lists, supplier and material lots, shared SOPs or software versions, and trend data for early signs.

Copying the action blindly is risky. A training fix that worked at a site with experienced staff may not suit a new site, and an equipment change may need its own validation at each site through local change control. Where the mechanism is uncertain, a time-limited assessment at each candidate site is a sensible first step.

Deciding not to extend should also be documented, with the reason, so a later failure elsewhere cannot be blamed on a silent gap.