The FDA guidance: General Principles of Software Validation focusses on two points related to revalidation. First, changes to the system must be evaluated for their relative impact to the particular company’s intended use for the system. For example, instrument support functionality changes may not be related to a user’s particular instrument configuration or may reflect unused features. From the vendor’s release documentation, it should be possible to determine what features and functionality have been updated, and what defects in the software have been corrected. Any changes should be compared against the intended use to determine any revalidation impact.
Second, whenever software is changed, the user should evaluate the change themselves, including some degree of regression testing to confirm that the change in the software or the updated software has not broken something else in some way that may have had unintended consequences. It is not uncommon, for example, when updating software for home computers or phones to find that features that worked before the update may not work afterwards.
