Practical Considerations for Implementing Targeted Mass Spectrometry for Urine Drug Testing in Clinical Laboratories

The use of tandem mass spectrometry (MS/MS) for urine drug testing has expanded in recent decades due to an increasing demand for compliance testing and confirmation of positive immunoassay results. While it has been demonstrated to be a robust methodology, MS/MS cannot control all variables associated with sample collection and testing. This review will touch on many factors of targeted MS/MS assays pertaining to drugs, metabolism, and proper method development. Various preanalytical and analytical considerations will be discussed, and best practice guidelines are suggested for controlling sample-to-sample variability.

Specimen Validity Testing in the Toxicology Laboratory

Ensuring accurate toxicology results is crucial in clinical, forensic, and workplace settings. Specimen validity testing is vital in assessing urine sample integrity to prevent tampering, substitution, or adulteration. This process includes pre-analytical checks like visual inspection and temperature monitoring, as well as analytical tests for pH, specific gravity, and creatinine concentrations. These measures help identify diluted or altered samples, ensuring reliable results. Vigilance from sampling facilities, laboratorians, and clinicians is essential, as positive test outcomes can significantly impact medical decisions, legal proceedings, and employment, making sample integrity critical to trustworthy toxicology testing.

Evaluation of Diagnostic Sensitivity and Specificity of a New Automatized Assay for Indirect Synthetic Urine Identification

Synthetic urine mimicking normal urine is difficult detectable by standard specimen validity testing. In this study, the VDx True Urine LD Test and True Urine SD Test, analysing 'long duration' (LD) and 'short duration' (SD) markers, were evaluated for their ability to detect synthetic urine. Two synthetic urines from the US market and 1188 real-life urine specimens were analysed for LD markers, SD markers, uric acid and temperature. Forty-seven specimens (set 1) showed uric acid and/or temperature suspicious results and were analysed by LC-MS/MS for 10 endogenous biomolecules. Diagnostic sensitivities and specificities were calculated for LD and SD markers based on uric acid and LC-MS/MS results of set 1. The false-positive rate of the SD marker was further evaluated with uric acid results of the other 1141 specimens (set 2). Additionally, direct synthetic urine markers were analysed by LC-(HR)MS. Uric acid and LC-MS/MS could identify synthetic urine. In one US synthetic urine, low concentrations of uric acid were found. Specimens of the Austrian/German region were reliably classified congruently by both methods. The LD and the SD markers detected both synthetic urines. For set 1, the LD had 100% sensitivity and 88.9% specificity, and the SD had 84.2% sensitivity and 44.4% specificity for authentic/synthetic specimens. In set 2, the SD marker specificity depended on the upper limit of the acceptance criteria. In one US synthetic urine, carbendazim was identified. Overall, several tests should be applied to confirm authentic or synthetic urine. Especially, simultaneous analysis of indirect and direct synthetic urine markers should be considered.

Successive electromembrane extraction: A new insight in simultaneous extraction of polar and non-polar metabolic molecules from biological samples

BACKGROUND

Simultaneous determination of different natures of analytes is of great significance for saving sample volumes and simplifying analytical procedures. However, sample preparation for the simultaneous extraction of polar and non-polar analytes represents a challenge in sample preparation. Inspired by the successive liquid-phase microextraction (sLPME) method for acidic and basic analytes that we previously developed, we first proposed an efficient successive electromembrane extraction (sEME) system by adjusting the acidity of the donor solution and using binary organic solvents for extraction of polar and non-polar targets from biological samples in this work.

RESULTS

We performed a detailed optimization of the sEME system. Here, carnitine (C0) and acylcarnitines were selected as model analytes since the demand increased especially in metabolomics studies. The combination of 2-nonanone and 2-nitrophenylpentyl ether (NPPE) was selected as supported liquid membranes (SLMs), and trichloroacetic acid (TCA) 100 % (v/v) was added to donor solution to adjust the acidity of the donor solution after the first sEME process (sEME-1). The recoveries of the targets in blood and urine were 47%-119% and 54%-118%, respectively. Moreover, the sEME systems were evaluated by liquid chromatography tandem mass spectrometry (LC-MS/MS) from biological samples. The limit of detection (LOD) and limit of quantitation (LOQ) of analytes were 0.03-1.33 ng mL-1 and 0.09-4.42 ng mL-1, respectively.

SIGNIFICANCE

sEME enabled the extraction of polar and non-polar analytes from the same sample under optimal extraction conditions for all target analytes, which provided ideas for efficient sEME of exogenous and endogenous analytes from biological samples for forensic, clinical, and epidemiological studies.

Rapid Characterization of the Potential Active of Sinomenine in Rats by Ultra-High-Performance Liquid Chromatography-Quadrupole-Exactive Orbitrap Mass Spectrometry and Molecular Docking

Sinomenium acutum (Thunb.) Rehd. et Wils is widely used in the treatment of rheumatoid arthritis, with its alkaloid compound sinomenine (SIN) being renowned for its significant anti-inflammatory properties. However, despite its widespread application, the in vivo anti-inflammatory mechanisms and metabolic pathways of SIN remain incompletely understood. This study established a rapid and reliable method based on an ultra-high-performance liquid chromatography method coupled with Quadrupole-Exactive Orbitrap mass spectrometry and molecular docking to identify and characterize SIN and 69 metabolites in rat plasma, urine, and feces, revealing primary metabolic pathways of hydroxylation, demethylation, sulfation, and glucuronidation. Molecular docking results revealed that phase I reactions, including dedimethylation, demethylation, dehydrogenation, and dihydroxylation, along with their composite reactions, were pivotal in influencing SIN's in vivo anti-inflammatory activity. M28, M36, and M59 are potentially the most anti-inflammatory active metabolites of SIN in vivo. This comprehensive analysis unveils SIN's metabolic pathways, offering insights into its biological processes and suggesting a novel approach for exploring active drug constituents. These findings pave the way for further understanding SIN's anti-inflammatory mechanisms, contributing significantly to the development of new therapeutic strategies.

Evaluation of biochemical assays and optimization of LC-MS-MS analysis for the detection of synthetic urine

Ensuring specimen validity is an essential aspect of toxicological laboratories. In recent years, substituting authentic urine specimens for synthetic urine (SU) has become increasingly popular. Such SU products consist of components expected in normal urine and show physiological values for specific gravity and pH. Thus, standard specimen validity testing may fail in revealing adulteration by SU. The present study investigated three methods to distinguish authentic and SU specimens: enzymatic detection of uric acid, the commercially available Axiom Test True SU and liquid chromatography coupled with (tandem) mass spectrometry (LC-MS-MS) analysis of 10 endogenous biomolecules. Additionally, novel direct markers of SU were investigated. Two specimen sets were analyzed by each method. Specimen set A consisted of eight SU products purchased from the Austrian/German market and 43 urine specimens from volunteers of known authenticity, which underwent double-blind analysis. Specimen set B consisted of 137 real urine specimens submitted for drug testing, which were selected due to initial suspicious test results in adulteration testing and reanalyzed by all three methods. Uric acid and LC-MS-MS-based endogenous biomolecule testing showed 100% sensitivity and specificity for set A. The commercial test had 87.5% sensitivity and 97.7% specificity for set A. For set B, uric acid and LC-MS-MS analysis showed almost similar results, even if uric acid was missing one presumptive authentic urine specimen according to LC-MS-MS findings. Nearly half of the SU assignments for the commercial test were presumptive false positives. New SU markers were observed for SU products from the Austrian/German market. One specimen in set B had both an endogenous biomolecule pattern and SU markers suggesting urine dilution with SU. In conclusion, several analytes or methods should be used rather than one, and the most reliable results are achieved if both indirect and direct markers of urine substitution are analyzed.

Advances in testing for sample manipulation in clinical and forensic toxicology - Part A: urine samples

In many countries, adherence testing is used to monitor consumption behavior or to prove abstinence. Urine and hair are most commonly used, although other biological fluids are available. Positive test results are usually associated with serious legal or economic consequences. Therefore, various sample manipulation and adulteration strategies are used to circumvent such a positive result. In these critical review articles on sample adulteration of urine (part A) and hair samples (part B) in the context of clinical and forensic toxicology, recent trends and strategies to improve sample adulteration and manipulation testing published in the past 10 years are described and discussed. Typical manipulation and adulteration strategies include undercutting the limits of detection/cut-off by dilution, substitution, and adulteration. New or alternative strategies for detecting sample manipulation attempts can be generally divided into improved detection of established urine validity markers and direct and indirect techniques or approaches to screening for new adulteration markers. In this part A of the review article, we focused on urine samples, where the focus in recent years has been on new (in)direct substitution markers, particularly for synthetic (fake) urine. Despite various and promising advances in detecting manipulation, it remains a challenge in clinical and forensic toxicology, and simple, reliable, specific, and objective markers/techniques are still lacking, for example, for synthetic urine.

Opioids for chronic pain management in patients with dialysis-dependent kidney failure

Chronic pain is highly prevalent among adults treated with maintenance haemodialysis (HD) and has profound negative effects. Over four decades, research has demonstrated that 50-80% of adult patients treated with HD report having pain. Half of patients with HD-dependent kidney failure (HDKF) have chronic moderate-to-severe pain, which is similar to the burden of pain in patients with cancer. However, pain management in patients with HDKF is often ineffective as most patients report that their pain is inadequately treated. Opioid analgesics are prescribed more frequently for patients receiving HD than for individuals in the general population with chronic pain, and are associated with increased morbidity, mortality and health-care resource use. Furthermore, current opioid prescribing patterns are frequently inconsistent with guideline-recommended care. Evidence for the effectiveness of opioids in pain management in general, and in patients with HDKF specifically, is lacking. Nonetheless, long-term opioid therapy has a role in the treatment of some patients when used selectively, carefully and combined with an ongoing assessment of risks and benefits. Here, we provide a comprehensive overview of the use of opioid therapy in patients with HDKF and chronic pain, including a discussion of buprenorphine, which has potential as an analgesic option for patients receiving HD owing to its unique pharmacological properties.

Cheating on forensic hair testing? Detection of potential biomarkers for cosmetically altered hair samples using untargeted hair metabolomics

Hair analysis has become an integral part in forensic toxicological laboratories for e.g. assessment of drug or alcohol abstinence. However, hair samples can be manipulated by cosmetic treatments, altering drug concentrations which eventually leads to false negative hair test results. In particular oxidative bleaching of hair samples under alkaline conditions significantly affects incorporated drug concentrations. To date, current techniques to detect cosmetic hair adulterations bear limitations such as the implementation of cut-off values or the requirement of specialized instrumentations. As a new approach, untargeted hair metabolomics analysis was applied to detect altered, endogenous biomolecules that could be used as biomarkers for oxidative cosmetic hair treatments. For this, genuine hair samples were treated in vitro with 9% hydrogen peroxide (H2O2) for 30 minutes. Untreated and treated hair samples were analyzed using liquid-chromatography high-resolution time-of-flight mass spectrometry. In total, 69 metabolites could be identified as significantly altered after hair bleaching. The majority of metabolites decreased after bleaching, yet totally degraded metabolites were most promising as suitable biomarkers. The formation of biomarker ratios of metabolites decreasing and increasing in concentrations improved the discrimination of untreated and treated hair samples. With the results of this study, the high variety of identified biomarkers now offers the possibility to include single biomarkers or biomarker selections into routine screening methods for improved data interpretation of hair test results.

HPLC-MS identification of acid degradation products of dolutegravir

Dolutegravir is an integrase strand transfer inhibitor used for the treatment of human immuno-deficiency virus infections. The present study was conducted in order to identify degradation products formed in acidic solution upon heating. The structures were assigned based on low resolution collision-induced dissociation tandem mass spectra as well as high resolution higher-energy collisional dissociation tandem mass spectra. The major degradation products resulted from hydrolytic opening of the oxepine ring leading to bis-hydroxy diastereomers (DP2 and DP3) as well as a mono-hydroxy derivative (DP1) as the result of dehydration of the diastereomers. Furthermore, two carboxylic acid derivatives (DP4 and DP5) could be identified, which can be explained as the result of the hydrolysis of the exocyclic amide bond of dolutegravir and DP1, respectively. During the fragmentation process of dolutegravir and its degradation products DP1 to DP3 a formal addition of oxygen resulting in the respective carboxylic acid fragments was detected. This could be evidenced based on high resolution masses of the fragments as well as the comparison of the MS/MS spectra of the fragments with the spectra of the carboxylic acids DP4 and DP5.

MASS SPECTROMETRY ANALYSIS OF DRUGS OF ABUSE: CHALLENGES AND EMERGING STRATEGIES

Mass spectrometry has been the "gold standard" for drugs of abuse (DoA) analysis for many decades because of the selectivity and sensitivity it affords. Recent progress in all aspects of mass spectrometry has seen significant developments in the field of DoA analysis. Mass spectrometry is particularly well suited to address the rapidly proliferating number of very high potency, novel psychoactive substances that are causing an alarming number of fatalities worldwide. This review surveys advancements in the areas of sample preparation, gas and liquid chromatography-mass spectrometry, as well as the rapidly emerging field of ambient ionization mass spectrometry. We have predominantly targeted literature progress over the past ten years and present our outlook for the future. © 2020 Periodicals, Inc. Mass Spec Rev.

Pitfalls in drug testing by hyphenated low- and high-resolution mass spectrometry

This paper reviews various pitfalls observed during developing, validation, application, and interpretation of drug testing approaches using GC-MS and low- and high-resolution LC-MS. They include sampling and storage of body samples, sample adulteration and contamination, analyte stability, sample preparation without or with cleavage of conjugates, extraction, derivatization, internal standardization, false negative and positive results by GC-MS or LC-MS screening and/or confirmation procedures including artifact formation, ion suppression or enhancement by electrospray ionization, and finally pitfalls in data interpretation. Conclusions and prospects close the Tutorial.

Evaluating Novel Markers for Specimen Validity Testing

CONTEXT.—

Synthetic urine products are commercially marketed for the purpose of specimen substitution for urine drug screens. These products are widely popular because they yield negative drug screen results, meet criteria for specimen validity testing, and are easily accessible and affordable. Current specimen validity criteria are ineffective for detecting these synthetic products, and new markers of specimen validity are required.

OBJECTIVE.—

To develop and evaluate a multicomponent liquid chromatography tandem mass spectrometry (LC-MS/MS) assay for urine specimen validity testing.

DESIGN.—

A quantitative LC-MS/MS assay was developed for caffeine, cotinine, theobromine, and urobilin in urine. The assay was applied to known synthetic urine products (n = 10) as well as human specimens received for pre-employment testing (n = 500), for-cause workplace testing (n = 100), and medical pain management monitoring (n = 200). Specimens devoid of all 4 validity markers were subjected to follow-up testing that involved microscopic urinalysis and comprehensive gas chromatography mass spectrometry for drugs, pharmaceuticals, hormones, and lipids.

RESULTS.—

Of the experimental groups, 10 of 10 synthetic urine products (100%), 12 of 500 pre-employment specimens (2.4%), and 4 of 200 pain management specimens (2.0%) failed the experimental LC-MS/MS assay. Follow-up testing indicated that each of the failed specimens was nonphysiologic in nature.

CONCLUSIONS.—

Simultaneous application of the 4 experimental validity markers appeared to be a robust method for detecting nonphysiologic specimens. New markers of specimen validity must be developed in order to identify commercially available synthetic urine products.

Metabolomic Strategies in Biomarker Research-New Approach for Indirect Identification of Drug Consumption and Sample Manipulation in Clinical and Forensic Toxicology?

Drug of abuse (DOA) consumption is a growing problem worldwide, particularly with increasing numbers of new psychoactive substances (NPS) entering the drug market. Generally, little information on their adverse effects and toxicity are available. The direct detection and identification of NPS is an analytical challenge due to their ephemerality on the drug scene. An approach that does not directly focus on the structural detection of an analyte or its metabolites, would be beneficial for this complex analytical scenario and the development of alternative screening methods could help to provide fast response on suspected NPS consumption. A metabolomics approach might represent such an alternative strategy for the identification of biomarkers for different questions in DOA testing. Metabolomics is the monitoring of changes in small (endogenous) molecules (<1,000 Da) in response to a certain stimulus, e.g., DOA consumption. For this review, a literature search targeting "metabolomics" and different DOAs or NPS was conducted. Thereby, different applications of metabolomic strategies in biomarker research for DOA identification were identified: (a) as an additional tool for metabolism studies bearing the major advantage that particularly a priori unknown or unexpected metabolites can be identified; and (b) for identification of endogenous biomarker or metabolite patterns, e.g., for synthetic cannabinoids or also to indirectly detect urine manipulation attempts by chemical adulteration or replacement with artificial urine samples. The majority of the currently available literature in that field, however, deals with metabolomic studies for DOAs to better assess their acute or chronic effects or to find biomarkers for drug addiction and tolerance. Certain changes in endogenous compounds are detected for all studied DOAs, but often similar compounds/pathways are influenced. When evaluating these studies with regard to possible biomarkers for drug consumption, the observed changes appear, albeit statistically significant, too small to reliably work as biomarker for drug consumption. Further, different drugs were shown to affect the same pathways. In conclusion, metabolomic approaches possess potential for detection of biomarkers indicating drug consumption. More studies, including more sensitive targeted analyses, multi-variant statistical models or deep-learning approaches are needed to fully explore the potential of omics science in DOA testing.

Evaluation of endogenous urinary biomarkers for indirect detection of urine adulteration attempts by five different chemical adulterants in mass spectrometry methods

Reliable detection of urine adulteration attempts to circumvent positive drug testing represents a critical step for laboratories in abstinence control settings. An ideal workflow for high-throughput testing would involve simultaneous detection of adulteration attempts in the same run with drug detection. Monitoring of degraded or oxidized endogenous urinary compounds as indirect markers has been previously evaluated for that purpose exemplified for the adulterant potassium nitrite (KNO₂ ). Fifteen, previously identified endogenous markers should now be evaluated for their general applicability to detect adulteration attempts for the adulterants hypochlorite-based bleach (NaOCl), peroxidase and peroxide (H₂ O₂ ), pyridinium chlorochromate (PCC), and iodine (I₂ ). Initial experiments revealed similar results for the tested adulterants regarding degradation of indolylacryloylglycine (IAG), uric acid (UA), or UA derivatives. 5-Hydroxyisourate (HIU), the oxidation product of UA, was however only formed by KNO₂ , PCC, and H₂ O₂ . Amino acids showed larger adulterant-dependent differences. All reactions were shown to be influenced by the adulterant concentration and the urinary pH with large variances depending on compound and adulterant. Except for HIU/PCC, all markers were stable within +/- 30% variation for all adulterants at -20°C. Receiver operating characteristics indicated best sensitivity and specificity over all adulterants for IAG (specificity 0.9, sensitivity 1.0) and UA (specificity 1.0, sensitivity 0.9). HIU gave best results for KNO₂ , PCC, and H₂ O₂ and N-acetylneuraminic acid for PCC and H₂ O₂ , respectively. When integrating a limited number of targets into existing screening methods, monitoring of UA, IAG, N-acetylneuraminic acid, and HIU is recommended.

Suitability evaluation of new endogenous biomarkers for the identification of nitrite-based urine adulteration in mass spectrometry methods

Urine adulteration to circumvent positive drug testing is a fundamental challenge for toxicological laboratories all over the world. Untargeted mass spectrometry (MS) methods used in metabolomics had previously revealed uric acid (UA), histidine, methylhistidine, and their oxidation products, for example 5-hydroxyisourate (HIU) as potential biomarkers for urine adulteration using potassium nitrite (KNO₂ ). These markers should be further evaluated for their reliability, stability, and routine applicability. Influence of KNO₂ concentration, urinary pH, reaction time, and stability at room temperature, 4°C, and - 20°C was determined in urine under varying conditions. Analysis was performed after protein precipitation with acetonitrile by liquid chromatography-high resolution mass spectrometry (LC-HRMS). Receiver operating characteristics (ROC) analysis was applied for cut-off evaluation after biomarker quantification (n = 100 per group). Blinded measurements (n = 50) were performed to check the general applicability to identify adulterated samples under routine conditions. The higher the adulterant concentration, the lower the concentrations of histidine, methylhistidine, and UA. In return, amounts of their oxidation products increased. Highest changes were observed under weak acid conditions (pH 4-5). Storage at -20°C ensured sufficient stability for all oxidative markers over one month. ROC evaluated biomarker performance and application to unknown samples revealed satisfying results, with HIU as the most suitable biomarker (positive predictive value (PPV) 100%), followed by UA (PPV 93%). HIU and UA proved suitable markers to identify urine adulteration using KNO₂ and are ready for implementation into routine MS procedures.