1. Trend analysis on method performance should be performed at regular intervals to evaluate the need to optimize the analytical procedure or to revalidate all or a part of the analytical procedure.
2. Applicants should periodically evaluate the appropriateness of a product’s analytical methods and consider new or alternative methods.
3. Revalidation:
 Change to analytical procedure
 change to manufacturing process or formulation
以上描述来自于 FDA 2015 方法验证的指南