USING VALIDATION EXPERIENCE TO SET PRODUCT ALERT LIMITS

Experience gained during validation can be used to fine-tune the process for
greater reliability. Several examples of changes being recommended based on
study findings may be found in the section of this chapter devoted to evaluation
of process data. Another application of the information gathered during validation
is in setting alert limits to be incorporated into the mechanism for product
release. The alert limits would be the control limits (UCL and LCL) calculated
as part of the review process for each analytical test; they could be made part
of the written specifications for product release.
The recommendation to use control limits calculated as part of validation
as alert limits is based on the expectation that test results from future production
should normally fall within these limits. Indeed, this is the essence of retrospective
validation. Furthermore, for a stable, centered process the control limits
would fall within the release specification for the test. Exceeding an alert limit
therefore would not necessarily delay product release but could precipitate an
investigation into the cause.
Requiring quality control to use validation experience to release product
achieves two objectives: it monitors conclusions reached during validation for
ongoing reliability and identifies a trend early before a rejection occurs. For
quality control laboratories using a laboratory information management system
(LIMS), routine performance of test result-alert limit comparisons can be automated.
Where such a system is not available, manually recorded test results
could be transferred to a stand-alone computer for trend analysis. An x¯ plot
depicting the process in relation to the alert and specification limits should be
considered for monitoring trends.