How to interpret NPS findings in hair?

Abstract

Objective

The spread of novel psychoactive substances (NPS) and novel synthetic opioids (NSO) in the worldwide drug market and their continuous increase in number and type, often with the purpose of bypassing the controlled substance legislation, represents an unceasing defy for forensic toxicologists, clinicians and enforcement authorities. This presentation will aim to provide information regarding the current state of the art for NPS analysis in hair.

Methods

The identification of NPS in biological samples is controversial, especially when the examined samples are limited, or the drug is promptly and extensively metabolized. This causes a lack of reliable literature data on the real NPS diffusion in different parts of the world and in different groups of populations. New technologies for the instrumental detection of NPS in alternative samples, namely hair, are now offering comprehensive information about the NPS use.

Results

The lack of detection and underreporting of NPS in biological samples makes it difficult to obtain complete qualitative and quantitative information about their prevalence. Instead, hair testing offers a unique perspective in the investigation of drug consumption, provided that a large panel of target analytes is considered. The prerequisite of targeted multi-analyte protocols used to investigate the diffusion of NPS/NSO is indeed that all the molecules of interest expected to be possibly present in the screened samples are included in the method. Parallelly, untargeted approaches or artificial intelligence tools have been being introduced to assist the identification of unknown compounds.

In this presentation, the available information obtainable from hair analysis and the results interpretation, in terms of trends and pattern of NPS/NSO prevalence, will be explored. In particular, (i) the diffusion of NPS/NSO, and (ii) the co-use of traditional and new drugs, will be discussed.

Discussion

One limitation of hair testing when testing for NPS/NSO is the sensitivity to detect exposure to different substances, although the technological development allows us today to achieve extremely low limits of detection when using last generation mass spectrometers. Other typical scenarios (passive exposure vs. active consumption, mindful vs. unaware intake, and the meaning of quantitative results, in terms of sporadic vs. chronic use or exposure) have been studied to shed light on possible criteria needed before a definitive interpretation of either positive or negative results can be safely given. Preliminary conclusions can be tentatively outlined, while other factors affecting drug incorporation (e.g. the role of melanin) have not been investigated yet. Nevertheless, updated targeted methods applied on different populations might become effective approaches for NPS/NSO screening to focus on patterns of drug exposure and produce valuable information for prevalence studies. Large screening panels using hair testing and taking into account the timely fluctuation of the market situation can also be applied to other individuals under periodic control (e.g., in workplace control or driving re-licensing) to check how frequently NPS/NSO are used, possibly in substitution of traditional drugs to escape a positive outcome. Finally, targeting specific markers can be used to delve into the diffusion compounds (e.g. opioids), which are clandestinely produced or sold.

Conclusions

When large populations are subjected to NPS/NSO hair analysis, then the gathered results can provide epidemiological data on trends and extent of use in the community. Therefore, epidemiology studies based on hair analysis (possibly in combination with other sources of information) can increase the knowledge about NPS/NSO use among at-risk populations and produce useful information to inform the policy-makers and the national health systems. New or especially problematic trends in drug use or adverse outcomes associated with use can be timely detected, thus allowing quick reports and prompt alert dissemination to the public, health professionals and national institutions.