It is possible for hair to be externally contaminated by drugs like cannabis or cocaine, which are smoked or snorted. Three steps are commonly employed to minimize the chance of external contamination causing misinterpretation of the results of a hair test. The first consists of decontamination of hair samples by washing the hair before analysis, the second is the use of cut-off levels, and the third is the detection of both the parent drugs and appropriate levels of their metabolite(s) in the hair sample. We propose an additional step for the assessment of drug use using hair samples combined with decontamination data. Hair samples from 186 drug users were analyzed along with their wash residues by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results of the hair analysis of the 140 samples for cocaine showed that 85.5% (N=89) of the samples passed 'cocaine use' criteria for metabolites ratios and 12.5% (N=13) for wash residue criteria (<10% of cocaine in the wash residue) leading to conclusive interpretation. Only two cases (1.9%) had an uncertain conclusion of drug consumption because cocaine levels in the wash residue were >10% of the levels in the hair. The results of the cannabis set of samples (N=46) were not as clear-cut, as a comparatively large number of samples (15.2%) had relatively high levels of THC in the wash residues. To use this approach, it is important that laboratories testing drugs in hair samples can demonstrate that the method utilized does not generate significant levels of the cocaine metabolites.

Hair biomarkers, ethyl glucuronide (EtG) and ethyl palmitate (EtPa), together with blood biomarker tests, carbohydrate-deficient transferrin (CDT) or phosphatidylethanol (PEth), are commonly used in identifying patterns of alcohol consumption as they possess different windows of detection. The detection of EtG in hair samples is mainly used in combination with EtPa when hair cosmetic treatments such as hair colouring and bleaching affect EtG levels. The main purpose of our study was to investigate the differences in frequency distribution of positive CDT and PEth results indicating alcohol had been used, when EtG and EtPa were not detected, where evidence of abstinence is paramount. Of the total 602 cases, for 179 (29.7%), neither EtG nor EtPa markers were detected. Of these, 0.5% of the cases produced positive CDT. However, 18.6% produced positive PEth, a significantly higher proportion. A similar pattern emerges when results are evaluated according to whether hair had been either cosmetically treated or untreated. When hair was untreated, one case produced positive CDT, and 19.3% were positive for PEth (median of 51 ng/ml). No cases of positive CDT results, but 20.8% of PEth were positive (median of 106.5 ng/ml) when hair samples had been cosmetically treated. Whether EtG or EtPa markers were detected or not, significantly higher proportions of PEth than CDT were seen. The results of this study substantiate the case for using hair EtG in conjunction with a PEth test, rather than CDT test, for efficient monitoring of recent and historical alcohol consumption.

The advantages of analysis of drugs in hair samples are recognised for the long window of detection, alongside easy sampling and long stability after sample collection. Alcohol markers, ethyl glucuronide (EtG) and total fatty acid ethyl esters (FAEEs) in hair are widely used for monitoring alcohol consumption for clinical and forensic purposes. Although stability of drugs and EtG in hair samples are documented to a certain extent, stability of FAEEs in hair samples after collection has not been reported. This study covered hair samples that had been tested for FAEEs on the day of arrival at the laboratory and retested between 4 days to 80 months later. The statistical analysis of the data set reveals significant lower FAEEs levels including ethyl palmitate ester levels (EtPa) when samples were re-tested for the second time after 6 days of storage under ideal conditions. Specifically, the results suggest that when measuring total FAEEs or solely EtPa in hair samples, the elapsed time between sample collection and analysis of the sample needs to be considered when interpreting the results. The recommendation is that whenever hair samples need to be tested for total FAEEs or EtPa, the analytical procedure needs to be performed within one week after collection in order to obtain meaningful results. The study results substantiate the case for the use of hair samples solely for the analysis of EtG, in conjunction with other measurements alcohol consumption such as full blood count (FBC), carbohydrate-deficient transferrin test (CDT), liver function test (LFT) or phosphatidylethanol (PEth) alongside clinical assessment for a more effective evaluation of alcohol consumption.

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.

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