Benefits of simultaneous screening and quantitation of drugs and their metabolites in post-mortem samples by liquid chromatography-high resolution mass spectrometry

Abstract

Compare a novel method for the simultaneous screening and quantitation of drugs and their metabolites in post-mortem blood and urine with an established two-step process involving a screen followed by quantitation using stand-alone assays. Determine if adoption of the novel method provides any benefits. Introduction: toxicological analysis of post-mortem samples may be required as part of the investigation into the death of an individual. Post-mortem blood and urine are usually screened to identify any compounds present. This is followed by separate quantitative assays to determine the concentrations of toxicologically significant compounds in the blood. This process is labour intensive, time-consuming, requires a broad range of analytical instrumentation and often requires a large sample volume. The consolidation of screening and quantitation into a single methodology has the potential to improve the efficiency of analysis, reduce the sample volume required and decrease turnaround times. Recent publications have demonstrated the suitability of liquid chromatography-high resolution mass spectrometry (LC-HRMS) for the combined screening and quantitation approach (Bidney, J Anal Toxicol., 2017, 41, 181–195; Partridge, J Anal Toxicol., 2018, 42, 220–231). However, there are no published studies which compare a combined approach by LC-HRMS with existing two-step workflows to determine if there are benefits to adopting the combined approach. Post-mortem blood ( n = 200) and urine ( n = 103) samples were screened using an established gas chromatography-mass spectrometry (GCMS) screen. Screening results were compared to those obtained using a novel LC-HRMS methodology using Q-ExactiveTM technology. Linear regression analysis was performed to compare quantitative blood results generated using LC-HRMS for 42 toxicologically significant compounds, with results generated using established stand-alone quantitative assays by GCMS and high performance-liquid chromatography (HPLC). Turnaround time data for quantitative results pre and post the introduction of LC-HRMS was compared to determine the difference in turnaround times. RLC-HRMS screening detected key compounds in 125% more instances than GCMS. LC-HRMS also showed a 60% increase in the number of compounds detected in comparison to GCMS. Quantitative values generated using the LC-HRMS assay were within ±10% of values obtained using the established methods by GCMS or HPLC. Retrospective analysis of turnaround times pre and post the adoption of LC-HRMS showed an average decrease in turnaround time of 32% (range 6-69%). Combining screening and quantitation reduced staffing requirements by 2 days for opiate quantitation and 1 day for most other analytes, and significantly reduced sample volume requirements. Recent increases in substance misuse have resulted in an increase in the number of post-mortem samples submitted for toxicological analysis (Niles, Popul Health Manag., 2020, 24, 43–51). Timely analysis of post-mortem samples is a requirement of the Chief Coroner in England (Chief Coroner, 2016). A comparison of results generated by LC-HRMS and an existing two-step workflow has shown that the LC-HRMS methodology is well placed to allow the laboratory to meet these challenges by improving the quality of screening results, reducing the sample volume required, and decreasing turnaround time and staffing requirements. LC-HRMS delivers significant decreases in turnaround time and staffing and sample volume requirements. It also increases the number of compounds detected. This demonstrates that adopting LC-HRMS has the potential to improve analytical quality and efficiency, allowing the toxicology laboratory to meet the challenges of increasing workload, a wider range of substance misuse, and decreasing turnaround times.