January 11, 2023

Many competitors’ Proficiency Testing (PT) programs use consensus-based statistics to establish assigned values, standard deviations, etc. and that may not be the best way to handle them, so AOAC has taken a different approach within ISO 13528:2022 Statistical methods for use in proficiency testing by interlaboratory comparison. Based on advice from statisticians and feedback from participants of competitor programs that use consensus, AOAC has adopted the use results submitted by pre-selected reference laboratories to determine the assigned value for each property in the PT study. The current status of testing for cannabinoids is such that there are few validated test methods for these compounds and matrices, and there are few CRMs for calibration and few reliable RMs for quality control. Accreditation and proficiency testing will bring some harmony to methods and product claims, but for the present time, the agreement among the large majority of laboratories is such that broad consensus statistics are not reliable references for many of the compounds included in a cannabis/hemp scheme. AOAC has identified four laboratories with recognized competence and a common understanding of the best methods for cannabis testing. The median of three to four results from these laboratories (with checks) will be considered the most reliable reference for other participants. AOAC will pay close attention to agreement of participant results and reference results and will work toward using a broader set of results as references for assigned values and performance limits.

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