The first international proficiency test on ketamine and norketamine in hair

This paper discusses the organization of the first international proficiency test (PT) programme on ketamine (K) and norketamine (NK) in hair samples. The primary objective of the programme was to evaluate the analytical capability of participating laboratories on hair analysis for K and NK via comparison of results. Authentic samples, instead of spiked samples were used in the programme to mimic the analysis of incorporated illicit drugs in real-life situations. Eight of the ten participating medical or forensic laboratories from Australia, France, Hong Kong, Italy, Singapore and the USA returned results to the organizer. Quantification methods from these laboratories were confined to GC–MS and LC–MS/MS. Performance assessment based on z-score indicated that only three laboratories achieved satisfactory results for both the analysis of K and NK. It was concluded that the overall performance of the participating laboratories was fair and there is still room for further improvement. Additional similarly designed PT programmes are recommended to be organized in order to encourage reliable measurements of illicit drugs in hair samples. Taking into account the substantial effect on the consensus values within limited number of data points, a recommendation on the provision of reference values assigned by accurate methods will be of benefit to small size PT programmes in the forensic field.