The standardisation of results on hair testing for drugs of abuse: an interlaboratory exercise in the Lombardy Region, Italy

Introduction: Hair testing for drugs of abuse is performed in Lombardy, the Italian Region with the highest number of inhabitants, by nine analytical laboratories accredited for forensic purposes, the most frequent being driving license regranting and workplace drug testing. Individuals undergoing hair testing for these purposes have the possibility to choose in which laboratory the analyses can be carried out. The aim of our study was to perform an interlaboratory exercise in order to verify the level of standardisation of hair testing for drugs of abuse of these nine accredited laboratories. Our intention was to reproduce the real case of an individual undergoing hair testing at the same time in different laboratories. Methods: Sixteen hair strands coming from different subjects were longitudinally divided in 3-4 aliquots and distributed to participating laboratories. Each laboratory received four samples, except two labs that received height and six samples, respectively, and the Reference laboratory that analysed all the 16 hair samples. The participant laboratories were requested to apply their routine methodologies. Results: All the participants (nine laboratories) analyzed opiates (morphine and 6-acethylmorphine) and cocainics (cocaine and benzoylecgonine) while only five analyzed methadone, amphetamines (amphetamine, methamphetamine, MDMA, MDA and MDEA) and THC. The majority of the participants (seven labs) performed acidic hydrolysis, to extract the drugs from the hair, and analysis by GC-MS, and two labs used LC-MS/MS. Eight laboratories performed initial screening tests by EMIT, ELISA or CEDIA. Results demonstrated a good qualitative performance for all the participants, since no false positive results were reported by any of them. Quantitative data were quite scattered, but less in samples with low concentrations of analytes than in those with higher concentrations. Conclusion: Results from this first regional inter-laboratory exercise show that, on one hand, individuals undergoing hair testing would have obtain the same qualitative results in any of the nine laboratories. On the other hand, the scatter in quantitative results could cause some inequalities if the interpretation of the data is required.