RELIABILITY OF THE VALIDATED PROCESS

Once the process has been validated, controls must be put into place to make
certain that operations continue to be performed as originally described. It is unreasonable
to assume that machines, instruments, plant services, and personnel will
remain static indefinitely. The FDA recognized the need for revalidation when it
issued the process validation guidelines [1]. A number of resources are available
to monitor for process drift. The quality assurance department can perform periodic
audits of manufacturing and laboratory practices against official procedures, review
equipment maintenance records including calibration history, and examine personnel
training programs. Any departures from original assumptions must be brought
to the attention of the validation team for evaluation of their impact on the process.
The CGMPs require the manufacturer of a product to conduct an annual
review of written records to evaluate product quality [6]. A number of authors have suggested that when done properly the review can highlight trends that
might otherwise go unnoticed. Lee discusses how analytical and production data,
as well as product complaint experience, can be arranged or collated for this
purpose [19]. The annual review would be an expedient means of monitoring
the conclusions reached during validation.
When planned changes are made to the process, equipment, or immediate
operating environment, the validation team should carefully assess the nature of
the change for its impact on different aspects of the process. It may not be
necessary to revalidate the entire process in cases in which the change can be
shown to be isolated [1]. There may be an opportunity to supplement the historical
experience with a prospective study specific to the planned change. To ensure
that this review occurs, a formal change control system must be in place.
It would also be appropriate to have in place a written plan describing the
company functions that have responsibility for monitoring the process.