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Terminology and Definitions Assay Validation System Suitability   Method Validation Protocol Method Transfer and Revalidation Summary and Conclusions

 

Method Validation Protocol

USP Chapter 1225 on validation of analytical methods specifically addresses terms and definitions, but leaves protocol and methodology open for interpretation. Some may argue that to some degree this was intentional, allowing flexibility in method validation. Laboratory personnel were given latitude to do "good science," however, the term "good science" means different things to different people. This is where the guidelines drafted as a result of the ICH process have begun to play a vital role. The ICH Guideline on Method Validation Methodology (now at step four of the ICH process as of this writing) begins to hint at experimental design and protocol. Before outlining an experimental design or protocol, however, it is necessary to make some basic assumptions. These assumptions include:

  • Selectivity has been previously demonstrated, or is measured and documented during the course of the validation protocol.
  • The method has been developed and optimized to the point where it makes sense investing time and effort in validating the method. Indeed, robustness should be the first parameter investigated.
  • Once data is generated, statistically valid approaches are used to evaluate it and make decisions, thus removing some of the subjectivity of method validation.
Given that the above three steps are addressed in one fashion or another, and bearing in mind the ICH methodology guidelines, and the requirements for validation depending on the type of analytical method (Tables 2 and 3), the following stepwise protocol can be proposed, as illustrated in Figure 9:
h hi
  • On day one, a linearity test over five levels for both the drug substance and dosage form is performed. Comparison of the results between the drug substance and dosage form fulfills the accuracy requirement.
  • At the end of day one, six repetitions are performed at 100% of the drug substance for repeatability.
  • Steps one and two are repeated over two additional days for intermediate precision.
  • LOQ is evaluated (as needed) by analyzing the drug substance over five levels, plus six repetitions for precision.
  • Baseline noise is evaluated over six repetitions of blank injections for the determination of LOD (if required).
Figure 9: Example Method Validation Protocol

In this manner, a logical stepwise approach to method validation using ICH methodology can be performed. As stated previously, the use of the appropriate statistical tests (Students-T, Cochran, Dixon and Fisher Tests) allows for less subjective decisions to be made regarding the data, reducing method validation to a much more objective undertaking. A rigorous use of statistics may in turn lend itself to some degree of automation in the future.