Competence, impartiality, and reliability of analytical data are ensured by the company’s participation in various Proficiency Test programs, carried out for all matrices and all analytical techniques used in our laboratories. Proficiency Tests, also known as Ring Tests, are interlaboratory tests designed to evaluate a given laboratory’s performance against predefined criteria by comparing with other laboratories (that is, in each interlaboratory circuit, participants perform one or more tests on the same sample). Each laboratory compares its analytical results with those obtained by others, thus performing a continuous self-assessment of its testing capabilities, while also undergoing a broad assessment of its overall performance. Laboratory performance assessments are expressed in the standardized form of a “z-score”, which statistically indicates how much the laboratory’s result differs from the most probable value, also known as the “assigned value”. Participation in interlaboratory proficiency tests is an     appropriate and independent self-control tool that helps improve the quality of the services provided. The national and international Proficiency Test providers, chosen by Bonassisa laboratories, are accredited according to the ISO/IEC 17043 standard.