Assay validation is based on the sound method development and sound criteria:

We rely on ICH and FDA guidelines for method validation. Before conducting Validation, a pre-validation study is conducted to explore the boundaries of the method. A pre-validation study provides the necessary information regarding the method's viability.  The method is re-developed, if the data obtained from the pre-validation study suggest that the method is not providing satisfactory results.

Method Development-Validation Life Cycle (MDVLC)