Cross validation in bioanalysis: Why, when and how?

During development of any drug candidate, use of more than one laboratory a nd /or multiple analytical procedures is common. Both situations often warr ant a cross validation study, however, presently there is no clear consensu s on the best study design for this. Moreover there are varying views on th e scenarios for which a cross validation study may be appropriate. Here the term 'cross validation' is differentiated from 'abbreviated validation', a nd a study design which accounts for assay variability (inter- and intra-ba tch) is presented in detail and proposed for application to inter-laborator y and inter-assay comparisons, The procedure uses estimations of inter- and intra-batch variability to calculate the number of replicates and batches necessary for the cross validation analysis of the data using analysis of v ariance, and a confidence interval approach is discussed.