Interpretation of Interlaboratory Trials Based on Accuracy Profiles

Validation is a very active field in analytical chemistry as illustrated by the numerous publications addressing this topic. According to most definitions, method validation is required to confirm the fitness-for-purpose of a particular analytical method. When considering interlaboratory validation, organization and calculation of parameters that describe method performance follow well-recognized standards. But the strategy used to verify whether the method is fit for a particular purpose is still under discussion. This paper presents a method for assessing the fitness-for-purpose of analytical methods based on results produced during interlaboratory trials. It is based on the construction of accuracy profiles, which can be used as a graphical decision support tool, and demonstrates how accuracy profiles, initially developed for in-house validations, can be extended to interlaboratory studies. These interlaboratory accuracy profiles use measurements collected under reproducibility conditions to give an interval where an expected proportion of future measurements will be located. This interval can be compared to an acceptability interval defined by the end-user to simply decide whether a method is fit-for-purpose or not. Several examples of application illustrate how data can be interpreted to draw conclusions about produced accuracy profiles and fitness-for-purpose. Hence, the accuracy profile could be used as a harmonized procedure to assess the performance of analytical methods that undergo interlaboratory validation.