Comparison of patterns of drug levels in head and body hair for medico-legal and workplace testing.

This paper presents concentration ranges and positivity rates for the common drugs, alcohol markers, new psychoactive substances (NPS) and anabolic steroids tested in head hair (n = 138,352) and body hair (n = 9532) on samples of hair from medico-legal (n = 112,033) and workplace (n = 35,851) sectors tested in our laboratory. Statistically significant higher levels were found more often in the various types of body hair when compared with head hair, but fewer cases exhibited lower levels. For example, statistically significant higher levels were detected in leg hair for cannabinol, THC, methadone and EtG and in beard hair for THC, THC-COOH and 6-acetylmorphine. In contrast, significantly lower levels were detected in axilla hair for cannabinol, THC and for EDDP, but median levels of mephedrone and DHEA were higher. Overall, higher medium levels were detected in head hair samples tested in the UK when compared with those previously published for samples tested in Germany, indicating geographical differences in drug consumption. Recommendations are, firstly, that hair testing laboratories use the results of their own compiled previous positive results for guidance when interpreting hair testing results and, secondly, that laboratories periodically share and combine their accumulated data with other testing laboratories. The latter could be used to establish reference ranges associated with specific technical procedures which would improve interlaboratory comparability and improve laboratory testing services when interpreting hair testing results.