Prior to proceeding to a discussion of method validation, it is important to differentiate
amongst the categories of analytical methods used in the biopharmaceutical industry for
product evaluation. In general, the analytical methods used can be divided into three
categories: (1) screening methods; (2) release and stability methods; and (3) characterization
methods. Screening methods are used to guide discovery research and process
development. These methods, which are often carried out in high-throughput format using
automation due to the large volumes of samples tested, do not typically follow any
validation guidance, since they are not intended for a QC environment. Nonetheless, it is
important to understand the capabilities and limitations of these methods so that the results
can be appropriately applied to making decisions during process and product development.
This is generally achieved through experience with the method in the analytical
development organization. The second class of methods, release and stability methods, are
intended for use in a Quality Control environment for product disposition and formal
stability studies. In addition, these methods are sometimes used in QC for in-process
samples in the form of in-process controls, which are used in the overall control strategy to
ensure product quality (and for which the validation strategy should mirror that used for
the release and stability methods). Whether used for release, stability, or in-process control
applications, these methods are generally validated prior to the validation (conformance)
lots to demonstrate that they have acceptable performance according to regulatory guidance
(discussed below). The third class of methods, characterization methods, are used to support
product characterization studies during reference standard characterization, process
characterization, comparability studies, and other product characterization activities, and
data from these studies is often submitted to regulatory agencies. Industry practice has
recently evolved to meet regulatory expectations that these methods will be qualified
according to written company procedures, though no formal written guidance is available,
and method validation is not expected for these analytical procedures.