After another decade: LC-MS/MS became routine in clinical diagnostics

Multiplexed Detection of Pancreatic Cancer by Combining a Nanoparticle-Enabled Blood Test and Plasma Levels of Acute-Phase Proteins

Simple Summary

In this study, a multiplexed strategy based on the combination of a nanoparticle-enabled blood test and serum levels of acute-phase proteins proved to be able to distinguish pancreatic cancer patients from healthy controls with a good and sex-dependent prediction ability. This study suggests a possible role of acute-phase proteins as pancreatic cancer biomarkers and paves the way for the development of multiplexed technologies for early cancer detection.

Abstract

The development of new tools for the early detection of pancreatic ductal adenocarcinoma (PDAC) represents an area of intense research. Recently, the concept has emerged that multiplexed detection of different signatures from a single biospecimen (e.g., saliva, blood, etc.) may exhibit better diagnostic capability than single biomarkers. In this work, we develop a multiplexed strategy for detecting PDAC by combining characterization of the nanoparticle (NP)-protein corona, i.e., the protein layer that surrounds NPs upon exposure to biological fluids and circulating levels of plasma proteins belonging to the acute phase protein (APPs) family. As a first step, we developed a nanoparticle-enabled blood (NEB) test that employed 600 nm graphene oxide (GO) nanosheets and human plasma (HP) (5% vol/vol) to produce 75 personalized protein coronas (25 from healthy subjects and 50 from PDAC patients). Isolation and characterization of protein corona patterns by 1-dimensional (1D) SDS-PAGE identified significant differences in the abundance of low-molecular-weight corona proteins (20–30 kDa) between healthy subjects and PDAC patients. Coupling the outcomes of the NEB test with the circulating levels of alpha 2 globulins, we detected PDAC with a global capacity of 83.3%. Notably, a version of the multiplexed detection strategy run on sex-disaggregated data provided substantially better classification accuracy for men (93.1% vs. 77.8%). Nanoliquid chromatography tandem mass spectrometry (nano-LC MS/MS) experiments allowed to correlate PDAC with an altered enrichment of Apolipoprotein A-I, Apolipoprotein D, Complement factor D, Alpha-1-antichymotrypsin and Alpha-1-antitrypsin in the personalized protein corona. Moreover, other significant changes in the protein corona of PDAC patients were found. Overall, the developed multiplexed strategy is a valid tool for PDAC detection and paves the way for the identification of new potential PDAC biomarkers.

Bloodstain Metabolite Markers: Discovery and Validation for Estimating Age of Bloodstain within 7 Days

Metabolomic research using analytical chemistry methods has been carried out in a wide range of research fields. However, research combining forensic science and metabolomics is rare. Determining the age of bloodstains could provide key information regarding when a crime was committed. Currently, validated methods for estimating the age of bloodstains are unavailable. Metabolites are intermediate and final products of chemical reactions. Therefore, they are less likely to be degraded than other components of blood under field conditions. In this study, metabolites in bloodstains were analyzed using liquid chromatography-mass spectrometry to discover and validate metabolic markers for determining the age of bloodstains within a week post-bleeding. Nontargeted analysis of bloodstain metabolites revealed statistically significant differences over time. Quantitative analysis of identified candidates via multiple reaction monitoring confirmed the statistical significance according to the age of bloodstain. Pyroglutamic acid, l-glutamine, acetylcarnitine, and adenosine 5'-monophosphate were selected as the final markers. The content of each marker exhibited a statistically significant and consistent tendency to decrease with the age of bloodstain. Furthermore, the effect of hemolysis was considered according to the blood fraction spots of the four markers. This study is the first to identify and validate metabolite markers that may help determine the age of bloodstains within a week post-bleeding. If applied to crime scenes as indicators of the age of bloodstains, they can be used as innovative and important tools for reconstructing crime scenes, suggesting initial investigative direction. This study highlights the forensic utility of blood metabolites ex vivo.

Review of the Use of Liquid Chromatography-Tandem Mass Spectrometry in Clinical Laboratories: Part II-Operations

Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is increasingly utilized in clinical laboratories because it has advantages in terms of specificity and sensitivity over other analytical technologies. These advantages come with additional responsibilities and challenges given that many assays and platforms are not provided to laboratories as a single kit or device. The skills, staff, and assays used in LC-MS/MS are internally developed by the laboratory, with relatively few exceptions. Hence, a laboratory that deploys LC-MS/MS assays must be conscientious of the practices and procedures adopted to overcome the challenges associated with the technology. This review discusses the post-development landscape of LC-MS/MS assays, including validation, quality assurance, operations, and troubleshooting. The content knowledge of LC-MS/MS users is quite broad and deep and spans multiple scientific fields, including biology, clinical chemistry, chromatography, engineering, and MS. However, there are no formal academic programs or specific literature to train laboratory staff on the fundamentals of LC-MS/MS beyond the reports on method development. Therefore, depending on their experience level, some readers may be familiar with aspects of the laboratory practices described herein, while others may be not. This review endeavors to assemble aspects of LC-MS/MS operations in the clinical laboratory to provide a framework for the thoughtful development and execution of LC-MS/MS applications.

Protocol for correlation analysis of the murine gut microbiome and meta-metabolome using 16S rDNA sequencing and UPLC-MS

The gut microbiota and metabolites play pivotal roles in the pathobiology of various diseases. Here, we describe a protocol to profile the gut microbiome and meta-metabolome of a mouse disease model for acute graft-versus-host disease. We describe steps for fecal sample collection and processing for 16S sequencing and UPLC-MS. Finally, we detail the steps for data analysis and exhibit multi-omic associations to correlate with pathology.

For complete details on the use and execution of this protocol, please refer to Li et al. (2020).

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Fecal 16S rDNA gene sequencing and LC-MS decodes gut microenvironment during disease

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Screening and correlation analysis between microbiome and metabolome

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Joint analysis of multi-omics data and correlation with pathology

Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics.

A rapid and standardized workflow for functional assessment of bacterial biosensors in fecal samples

Gut metabolites are pivotal mediators of host-microbiome interactions and provide an important window on human physiology and disease. However, current methods to monitor gut metabolites rely on heavy and expensive technologies such as liquid chromatography-mass spectrometry (LC-MS). In that context, robust, fast, field-deployable, and cost-effective strategies for monitoring fecal metabolites would support large-scale functional studies and routine monitoring of metabolites biomarkers associated with pathological conditions. Living cells are an attractive option to engineer biosensors due to their ability to detect and process many environmental signals and their self-replicating nature. Here we optimized a workflow for feces processing that supports metabolite detection using bacterial biosensors. We show that simple centrifugation and filtration steps remove host microbes and support reproducible preparation of a physiological-derived media retaining important characteristics of human feces, such as matrix effects and endogenous metabolites. We measure the performance of bacterial biosensors for benzoate, lactate, anhydrotetracycline, and bile acids, and find that they are highly sensitive to fecal matrices. However, encapsulating the bacteria in hydrogel helps reduce this inhibitory effect. Sensitivity to matrix effects is biosensor-dependent but also varies between individuals, highlighting the need for case-by-case optimization for biosensors’ operation in feces. Finally, by detecting endogenous bile acids, we demonstrate that bacterial biosensors could be used for future metabolite monitoring in feces. This work lays the foundation for the optimization and use of bacterial biosensors for fecal metabolites monitoring. In the future, our method could also allow rapid pre-prototyping of engineered bacteria designed to operate in the gut, with applications to in situ diagnostics and therapeutics.

Phosphoproteomic analysis reveals the effects of sleep deprivation on the hippocampus in mice

Sleep is essential for brain physiology, including nerve repair, neuronal activity, and metabolite clearance. The hippocampus is responsible for short-term memory, long-term memory, and spatial positioning. Herein, we investigated the effects of sleep deprivation on protein phosphorylation and related signaling pathways in the mouse hippocampus. The treatment group was sleep deprived for nine hours a day, and at the end of sleep deprivation, we removed the hippocampus for phosphoproteomic analysis. Through this analysis, we identified 65 sites and 27 proteins whose phosphorylation was significantly different between sleep-deprived animals and control animals. Differentially phosphorylated proteins (DPPs) were mainly distributed in the postsynaptic density, cytoplasm, and synapse. They participated in metabolic pathways, endocytosis, oxidative phosphorylation and other processes, and they were associated with Huntington's disease, Parkinson's disease, Alzheimer's disease, etc. Functional analysis of the phosphoproteome shows that sleep deprivation significantly affects the level of protein phosphorylation in the hippocampus of mice. This is the first reported study that has used phosphoproteomics to investigate the effects of sleep deprivation on hypothalamic regions. This study provides data resources that can serve as a valuable reference for sleep mechanism research, sleep disorder treatment, and drug development.

Development of Cross-Reactive Antibodies for the Identification and Treatment of Synthetic Cannabinoid Receptor Agonist Toxicity

Synthetic cannabinoid receptor agonists (SCRAs) are compounds that mimic the pharmacology of the psychoactive components in cannabis. These compounds are structurally diverse, inexpensive, commercially available, and difficult to identify with modern analytical methods, making them highly accessible for recreational use. Suspected SCRA toxicity, which can present with a breadth of cardiovascular, gastrointestinal, and neurological disturbances, is currently addressed through symptom management followed by a toxicological screening that often occurs long after patient discharge. Here, we report the development of four cross-reactive anti-SCRA bioconjugate vaccines as a platform for developing improved diagnostic and therapeutic interventions against SCRA intoxication, using SCRA-resembling small molecule haptens that combine common subregional motifs occurring within and across different generations of SCRA molecules. Using a combination of multiplexed competitive ELISA screening and chemoinformatic analyses, it was found that the antibodies resulting from vaccination with these bioconjugates demonstrated their ability to detect multiple SCRAs with a Tanimoto minimum common structure score of 0.6 or greater, at concentrations below 8 ng/mL. The scope of SCRAs detectable using these haptens was found to include both bioisosteric and non-bioisosteric variants within the core and tail subregions, as well as SCRAs bearing valine-like head subregions, which are not addressed by commercially available ELISA screening approaches. Vaccination with these bioconjugates was also found to prevent the changes in locomotion and body temperature that were induced by a panel of SCRAs at doses of 1 and 3 mg/kg. Further refinement of this genericized hapten design and cross-reactivity-prioritizing approach may enable the rapid detection of otherwise cryptic SCRAs that arise during overdose outbreaks, and could ultimately lead to identification of monoclonal antibody species applicable for overdose reversal.

Profiling gut microbiota and bile acid metabolism in critically ill children

Broad-spectrum antimicrobial use during the treatment of critical illness influences gastrointestinal fermentation endpoints, host immune response and metabolic activity including the conversion of primary to secondary bile acids. We previously observed reduced fermentation capacity in the faecal microbiota of critically ill children upon hospital admission. Here, we further explore the timecourse of the relationship between the microbiome and bile acid profile in faecal samples collected from critically ill children. The microbiome was assayed by sequencing of the 16S rRNA gene, and faecal water bile acids were measured by liquid chromatography mass spectrometry. In comparison to admission faecal samples, members of the Lachnospiraceae recovered during the late-acute phase (days 8-10) of hospitalisation. Patients with infections had a lower proportion of Lachnospiraceae in their gut microbiota than controls and patients with primary admitting diagnoses. Keystone species linked to ecological recovery were observed to decline with the length of PICU admission. These species were further suppressed in patients with systemic infection, respiratory failure, and undergoing surgery. Bile acid composition recovers quickly after intervention for critical illness which may be aided by the compositional shift in Lachnospiraceae. Our findings suggest gut microbiota recovery can be readily assessed via measurement of faecal bile acids.

Testosterone analysis in prostate cancer patients

Testosterone is an essential steroid hormone associated with a wide variety of biological processes in humans. In prostate cancer, androgen signaling is an important driver of tumor cell growth. Depletion of gonadal testosterone, achieved by surgical or chemical castration, prevents androgenic signaling and temporally reduces, stops or reverses tumor growth before inevitable progression to castration-resistant prostate cancer occurs. Additional treatment strategies targeting androgenic signaling have become available, although these are without curative intent. While circulating testosterone is also associated with disease risk and potential clinical utility, the main use in the clinical lab is monitoring adequate castration and subsequent resistance to therapy. Adequate castrate testosterone concentrations are currently based on over 50 year-old double-isotope derivative assays that are disputed in automated immunoassay (IA) analysis. The debate has been further fueled with the introduction of mass spectrometry-based assays for testosterone, offering a substantial increase in sensitivity and specificity. In this review, we discuss testosterone regulation and androgen deprivation therapy in prostate cancer. We provide an overview of the developments in testosterone analysis for monitoring adequate castration and resistance to therapy. Current clinical practice and future clinical utility will be discussed. Finally, clinical and research recommendations will be presented.

Protein Profiling of Breast Cancer for Treatment Decision-Making

The increasing use of neoadjuvant therapy has resulted in therapeutic decisions being made on the basis of diagnostic needle core biopsy. For many patients, this method might yield the only fragment of tumor available for biomarker analysis, necessitating judicious use. Many multiplex protein analytic methods have been developed that employ fluorescence or other tags to overcome the limitations of immunohistochemistry while still retaining the spatial annotation. Interpretation of the data can be difficult because of the limitations of the human eye. Computational deconvolution of the signals may be necessary for some of these methods to enable identification of cell-specific localization and coexpression of biomarkers. Herein, we present the different methods that are coming of age and their application in cancer research, with a focus on breast cancer. We also discuss the limitations, which include high costs and long turnaround times. The methods are also based on the premise that preanalytical factors will have identical impact on all proteins analyzed. There is a need to establish standards to normalize the data and enable cross-sample comparisons. In spite of these limitations, the multiplex technologies are extremely valuable discovery tools and can provide novel insights into the biology of cancer and mechanisms of drug resistance.

A Flexible Tool to Correct Superimposed Mass Isotopologue Distributions in GC-APCI-MS Flux Experiments

The investigation of metabolic fluxes and metabolite distributions within cells by means of tracer molecules is a valuable tool to unravel the complexity of biological systems. Technological advances in mass spectrometry (MS) technology such as atmospheric pressure chemical ionization (APCI) coupled with high resolution (HR), not only allows for highly sensitive analyses but also broadens the usefulness of tracer-based experiments, as interesting signals can be annotated de novo when not yet present in a compound library. However, several effects in the APCI ion source, i.e., fragmentation and rearrangement, lead to superimposed mass isotopologue distributions (MID) within the mass spectra, which need to be corrected during data evaluation as they will impair enrichment calculation otherwise. Here, we present and evaluate a novel software tool to automatically perform such corrections. We discuss the different effects, explain the implemented algorithm, and show its application on several experimental datasets. This adjustable tool is available as an R package from CRAN.

Dynamic Changes in the Proteome of Early Bovine Embryos Developed In Vivo

Early embryo development is a dynamic process involving important molecular and structural changes leading to the embryonic genome activation (EGA) and early cell lineage differentiation. Our aim was to elucidate proteomic changes in bovine embryos developed in vivo. Eleven females were used as embryo donors and pools of embryos at the 4–6 cell, 8–12 cell, morula, compact morula and blastocyst stages were analyzed by nanoliquid chromatography coupled with label free quantitative mass spectrometry. A total of 2,757 proteins were identified, of which 1,950 were quantitatively analyzed. Principal component analysis of data showed a clear separation of embryo pools according to their developmental stage. The hierarchical clustering of differentially abundant proteins evidenced a first cluster of 626 proteins that increased in abundance during development and a second cluster of 400 proteins that decreased in abundance during development, with most significant changes at the time of EGA and blastocyst formation. The main pathways and processes overrepresented among upregulated proteins were RNA metabolism, protein translation and ribosome biogenesis, whereas Golgi vesicle transport and protein processing in endoplasmic reticulum were overrepresented among downregulated proteins. The pairwise comparison between stages allowed us to identify specific protein interaction networks and metabolic pathways at the time of EGA, morula compaction and blastocyst formation. This is the first comprehensive study of proteome dynamics in non-rodent mammalian embryos developed in vivo. These data provide a number of protein candidates that will be useful for further mechanistic and functional studies.

Applications of Tandem Mass Spectrometry (MS/MS) in Protein Analysis for Biomedical Research

Mass Spectrometry (MS) allows the analysis of proteins and peptides through a variety of methods, such as Electrospray Ionization-Mass Spectrometry (ESI-MS) or Matrix-Assisted Laser Desorption Ionization-Mass Spectrometry (MALDI-MS). These methods allow identification of the mass of a protein or a peptide as intact molecules or the identification of a protein through peptide-mass fingerprinting generated upon enzymatic digestion. Tandem mass spectrometry (MS/MS) allows the fragmentation of proteins and peptides to determine the amino acid sequence of proteins (top-down and middle-down proteomics) and peptides (bottom-up proteomics). Furthermore, tandem mass spectrometry also allows the identification of post-translational modifications (PTMs) of proteins and peptides. Here, we discuss the application of MS/MS in biomedical research, indicating specific examples for the identification of proteins or peptides and their PTMs as relevant biomarkers for diagnostic and therapy.

Clinical Mass Spectrometry in Immunosuppressant Analysis: Toward a Full Automation?

The analysis of immunosuppressive drugs allows the physician to monitor, and eventually correct, immunosuppressive therapy. The panel of molecules under evaluation includes cyclosporine A (CsA), tacrolimus, sirolimus, and everolimus. Initially, assays were performed by immunometric methods, but in the past few years this methodology has been largely superseded by a more accurate and specific technique, liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS), which is now considered the “gold standard” for immunosuppressant analysis. Both LC-MS/MS and often also immunoassays require a preanalytical manual sample preparation, which involves time-consuming sequential operations whose traceability is often hampered and adds up to the probability of gross errors. The aim of this work was to compare an “open” LC-MS/MS with a fully automated system, consisting of LC instrumentation combined with a triple quadrupole MS, named Thermo ScientificTM CascadionTM SM Clinical Analyzer (Cascadion). Such automated systems suit the requirements of the reference method and are designed to completely eliminate all of the manual procedures. More than 2000 immunosuppressant samples were analyzed both with the open LC-MS/MS and with Cascadion. Statistics allowed the evaluation of linearity, intra- and inter-assay CV%, bias %, limit of detection and of quantitation, and Passing–Bablok and Bland–Altman plots. Results indicated a good correlation between the two methods. In both cases, methods confirmed their suitability for diagnostic settings. Cascadion could provide support when the presence of specialized personnel is lacking, and/or when great productivity and continuous workflow are required.

Assignment of a Reference Value of Total Cow’s Milk Protein Content in Baked Cookies Used in an Interlaboratory Comparison

Interlaboratory comparisons (ILC) in the food allergens field mainly rely on the use of consensus values per applied methodology or even per type of an ELISA test kit. Results suggest good reproducibility; however, possible biases may not be recognized since metrological traceability to an independent reference is lacking. The work presented here utilizes isotope dilution mass spectrometry (IDMS) to assign a reference value of the total cow’s milk protein (TCMP) content in a baked cookie and its associated uncertainty. TCMP consists of several individual proteins, of which five (representing 92%) served us as markers for TCMP. Per marker, one to four proteotypic peptides were selected for the quantification. These were synthesized, and the mass fractions of respective reference solutions were determined with peptide-impurity-corrected amino acid analysis to establish traceability to SI units. Stable isotope labelled (“heavy”) analogues of the proteotypic peptides were also synthesized and blended with extracts of the test material or the reference solutions for IDMS. Through careful measurement design minimizing biases, well-defined model equations were developed, allowing appropriate estimation of the associated uncertainty. The determined reference value of 11.8 ± 1.1 mg TCMP/kg cookie was used for scoring of a novel ILC.

Preparative capillary electrophoresis (CE) fractionation of protein digests improves protein and peptide identification in bottom-up proteomics

Reversed-phase liquid chromatography (RPLC) is widely used to reduce sample complexity prior to mass spectrometry (MS) analysis in bottom-up proteomics. Improving peptide separation in complex samples enables lower-abundance proteins to be identified. Multidimensional separations that combine orthogonal separation modes improve protein and peptide identifications over RPLC alone. Here we report a preparative capillary electrophoresis (CE) fractionation method that combines CE and RPLC separations. Using this method, we demonstrate improved protein and peptide identification in a tryptic digest of E. coli cell lysate, with 132 ± 33% more protein identifications and 185 ± 65% more peptide identifications over non-fractionated samples. Fractionation enables detection of lower-abundance proteins in this complex sample. We demonstrate improved coverage of ovarian cancer biomarker MUC16 isolated from conditioned cell media, with 6.73% sequence coverage using CE fractionation compared to 2.74% coverage without preparative fractionation. This new method will allow researchers performing bottom-up proteomics to harness the advantages of CE separations while using widely available LC-MS/MS instrumentation.

An automated magnetic bead extraction method for measuring plasma metanephrines and 3-methoxytyramine using liquid chromatography tandem mass spectrometry

Liquid chromatography tandem mass spectrometry (LC-MS/MS) is used routinely in clinical diagnostics; however, automating the sample pretreatment is challenging. We established and evaluated an automated method based on the magnetic bead extraction principle (MBE) to measure normetanephrine (NMN), metanephrine (MN), and 3-methoxytyramine (3-MT). The target analytes were extracted, purified, and concentrated using different solvents and chemical bond-modified magnetic beads transferred via a magnetic bar. The linearity, recovery, matrix effect, and precision of MBE were evaluated thoroughly, and compared with traditional solid-phase extraction (SPE) using 131 plasma samples. The chromatography peaks of metanephrines and 3-MT, extracted via MBE, are symmetrical, without interfering peaks. The linearity was excellent with correlation coefficient (r) > 0.99. The MBE exhibited good reproducibility with within-run coefficient variations (CVs) of 1.96-2.00%, 4.06-5.75%, and 3.89-4.90% for MN, NMN, and 3-MT, respectively. The total CVs for MN, NMN, and 3-MT were 1.96-2.80%, 5.12-5.75%, and 5.44-6.27%, respectively. The relative recoveries for MN, NMN, and 3-MT varied between 93.5 and 107.4%, whereas their biases were all within 10%. The results for MN, NMN, and 3-MT extracted via MBE compared with SPE exhibited excellent correlation, with r > 0.99; the mean bias% for MN, NMN, and 3-MT were small (-2.9%, -3.2%, and -3.2%, respectively). In conclusion, the automated MBE method for measuring plasma metanephrines and 3-MT can be applied in future routine clinical diagnostics, and the MBE principle may indicate a new era for LC-MS/MS in clinical application.

Qualitative and quantitative analysis of ephedrine stimulants in urine by ultra-performance liquid chromatography-tandem mass spectrometry

RATIONALE

Ephedrine analogues are stimulants that are explicitly required to be quantified and characterized in the Anti-Doping Prohibited List of the World Anti-Doping Agency. Given the difficulty of distinguishing diastereoisomers, the qualitative and quantitative analyses of ephedrine diastereoisomers are difficult.

METHODS

An ultra-performance liquid chromatography-tandem mass spectrometry (UHPLC/MS/MS) method was developed to detect five ephedrine analogues, and two pairs of diastereoisomers were identified using this method. The samples were analyzed qualitatively and quantitatively using a tandem mass spectrometer with an electrospray ionization source in multiple reaction detection mode after one-step dilution.

RESULTS

The effective detection limits of this method were below 0.5 ng/mL. A matrix effect (range: 83.4% to 102%) was observed in quality control samples. The intra- and inter-day precision was lower than 9.16% and 8.60%, respectively, and the accuracy was within ±8.0%.

CONCLUSIONS

The method is efficient, accurate, stable and sensitive, and fully meets the requirements for the detection of ephedrine substances in stimulants.

Quantification of Antibiotics in Patient Samples: State of the Art in Standardization and Proficiency Testing

BACKGROUND

For many antibiotics, the convenient one-fits-all dosing regimen had to be abandoned. Owing to highly variable pharmacokinetics, therapeutic drug monitoring has become an indispensable prerequisite. It is based on a suitable measuring method, sample materials, and standardization. Appropriate quality control including external quality assessment (EQA) is essential. For many antibiotics, EQAs have been established for many decades, whereas others have only lately been introduced. This article gives an insight into the state of the art regarding the therapeutic drug monitoring of antibiotics regarding standardization, EQAs, and reference measurement procedures (RMPs).

METHODS

An overview of the currently available international EQA schemes for antibiotics and a literature overview of available RMPs are given. EQAs including gentamicin and vancomycin have been offered by German providers for more than 25 years. The period 2000-2020 was selected for a detailed analysis. The experiences with a new EQA including linezolid, meropenem, and piperacillin are described.

RESULTS

EQAs for gentamicin and vancomycin are provided in many countries. Those for linezolid, meropenem, and piperacillin do not seem to be very common. Most of the antibiotics monitored for decades are measured by commercially available assays. EQAs for linezolid, meropenem, and piperacillin introduced in 2018 were rapidly accepted in Germany. Methods reported in this study were HPLC based either with UV or mass spectrometric detection. The number of participants succeeding was comparable between UV and mass spectrometry. Candidate RMPs for gentamicin, vancomycin, and linezolid based on isotope dilution mass spectrometry were published.

CONCLUSIONS

EQAs are offered regularly for many antibiotics worldwide. The results of EQAs in Germany generally compare well, but there is potential for improvement. Both immunoassays and HPLC-based methods work properly in EQAs evaluated in Germany. From a quality control perspective, fast and inexpensive methods may be selected without endangering the patient's health based on clinical needs.

Isotope dilution LC-MS/MS quantification of the cystic fibrosis transmembrane conductance regulator (CFTR) modulators ivacaftor, lumacaftor, tezacaftor, elexacaftor, and their major metabolites in human serum

OBJECTIVES

Cystic fibrosis (CF) transmembrane conductance regulator (CFTR) modulators have revolutionized the therapeutic landscape in CF treatment. These vital drugs are extensively metabolized via CYP3A, so caution must be exercised in multimodal CF therapy because of the risk of adverse drug interactions. Our goal was to develop a highly sensitive assay for the purpose of therapeutic drug monitoring (TDM) in diagnostic laboratories.

METHODS

After protein precipitation, the CFTR modulators ivacaftor, lumacaftor, tezacaftor, elexacaftor, and their metabolites ivacaftor-M1, ivacaftor-M6, and tezacaftor-M1 were separated with a two-dimensional chromatography setup within 5 min, and quantified with stable isotope-labeled internal standards. The method was validated according to the European Medicines Agency (EMA) guideline on bioanalytical method validation and applied to CF patient samples.

RESULTS

Inaccuracy was ≤7.0% and the imprecision coefficient of variation (CV) was ≤8.3% for all quality controls (QCs). The method consistently compensated for matrix effects, recovery, and process efficiency were 105-115 and 96.5-103%, respectively. Analysis of CF serum samples provided concentrations comparable to the pharmacokinetic profile data reported in the EMA assessment report for the triple combination therapy Kaftrio.

CONCLUSIONS

We hereby present a robust and highly selective isotope dilution liquid chromatography tandem mass spectrometry (ID-LC-MS/MS) assay for the simultaneous quantification of the so far approved CFTR modulators and their metabolites in human serum. The assay is suitable for state-of-the-art pharmacovigilance of CFTR modulator therapy in CF patients, in order to maximize safety and efficacy, and also to establish dose-response relationships in clinical trials.

Small volume retinol binding protein measurement by liquid chromatography-tandem mass spectrometry

BACKGROUND

The measurement of plasma concentrations of retinol binding protein is a component of nutritional assessment in neonatal intensive care. However, serial testing in newborns is hampered by the limited amount of blood that can be sampled. Limitations are most severe with preterm infants, for whom close monitoring may be most important.

METHODS

We developed an assay to quantify retinol binding protein using trypsin digestion and liquid chromatography-tandem mass spectrometry, which requires a serum or plasma volume of 5 µl. Additionally, we validated the method according to current recommendations and performed comparison with a standard nephelometry platform in clinical use.

RESULTS

The assay demonstrated linearity from below 1 mg/dL (0.48 µM) to more than 20 mg/dL (9.7 µM), and an imprecision of 11.8% at 0.43 mg/dL (0.21 µM). The distribution of results observed with the new method was different when compared with nephelometry.

CONCLUSION

Liquid chromatography-tandem mass spectrometry facilitated testing a smaller sample volume, thereby increasing the ability to monitor key nutritional markers in premature infants. The differences in results compared with a commercially-available nephelometric assay revealed questionable results for lower concentrations by immunoassay.

Infrared multiple photon dissociation (IRMPD) spectroscopy and its potential for the clinical laboratory

Infrared multiple photon dissociation (IRMPD) spectroscopy is a powerful tool used to probe the vibrational modes-and, by extension, the structure-of an ion within an ion trap mass spectrometer. Compared to traditional FTIR spectroscopy, IRMPD spectroscopy has advantages including its sensitivity and its relative ability to handle complex mixtures. While IRMPD has historically been a technique for fundamental analyses, it is increasingly being applied in a more analytical fashion. Notable recent demonstrations pertinent to the clinical laboratory and adjacent interests include analysis of modified amino acids/residues and carbohydrates, structural elucidation (including isomeric differentiation) of metabolites, identification of novel illicit drugs, and structural studies of various biomolecules and pharmaceuticals. Improvements in analysis time, coupling to commercial instruments, and integration with separations methods are all drivers toward the realization of these analytical applications. Additional improvements in these areas, along with advances in benchtop tunable IR sources and increased cross-discipline collaboration, will continue to drive innovation and widespread adoption. The goal of this tutorial article is to briefly present the fundamentals and instrumentation of IRMPD spectroscopy, as an overview of the utility of this technique for helping to answer questions relevant to clinical analysis, and to highlight limitations to widespread adoption, as well as promising directions in which the field may be heading.

Detection of SARS-CoV-2 by Mass Spectrometry

Amplification of viral ribonucleic acid by real-time reverse transcriptase polymerase chain reaction is the gold standard to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, alternative reliable, fast, and cost-effective methods for the detection of SARS-CoV-2 are still needed. In this chapter, the mass spectrometry-based detection of amplified polymerase chain reaction products of SARS-CoV-2 genes from oral or nasopharyngeal swabs is described. The respective SARS-CoV-2 test has previously been shown to meet standard quality criteria and was therefore approved by the authorities in Europe and the USA.

Coronavirus Disease 2019 (COVID-19): Emerging detection technologies and auxiliary analysis

The ongoing COVID-19 pandemic constitutes a new challenge for public health. Prevention and control of infection have become urgent and serious issues. To meet the clinical demand for higher accuracy of COVID-19 detection, the development of fast and efficient methods represents an important step. The most common methods of COVID-19 diagnosis, relying on real-time fluorescent quantitative PCR(RT-qPCR), computed tomography, and new-generation sequencing technologies, have a series of advantages, especially for early diagnosis and screening. In addition, joint efforts of researchers all over the world have led to the development of other rapid detection methods with high sensitivity, ease of use, cost-effectiveness, or allowing multiplex analysis based on technologies such as dPCR, ELISA, fluorescence immunochromatography assay, and the microfluidic detection chip method. The main goal of this review was to provide a critical discussion on the development and application of these different analytical methods, which based on etiology, serology, and molecular biology, as well as to compare their respective advantages and disadvantages. In addition to these methods, hematology and biochemistry, as well as auxiliary analysis based on pathological anatomy, ultrasonography, and cytokine detection, will help understand COVID-19 pathogenesis. Together, these technologies may promote and open new windows to unravel issues surrounding symptomatic and asymptomatic COVID-19 infections and improve clinical strategies toward reducing mortality.

A rapid and universal liquid chromatograph-mass spectrometry-based platform, refmAb-Q nSMOL, for monitoring monoclonal antibody therapeutics

Accurate multiplexed quantitation of unique signature peptides derived from monoclonal antibody therapeutics with a universal reference antibody refmAb-Q using Fab-selective proteolysis nSMOL coupled with LC-MS/MS.

Liquid chromatography–tandem mass spectrometry for clinical diagnostics

Mass spectrometry is a powerful analytical tool used for the analysis of a wide range of substances and matrices; it is increasingly utilized for clinical applications in laboratory medicine. This Primer includes an overview of basic mass spectrometry concepts, focusing primarily on tandem mass spectrometry. We discuss experimental considerations and quality management, and provide an overview of some key applications in the clinic. Lastly, the Primer discusses significant challenges for implementation of mass spectrometry in clinical laboratories and provides an outlook of where there are emerging clinical applications for this technology.

Tandem mass spectrometry is increasingly utilized for clinical applications in laboratory medicine. In this Primer, Thomas et al. discuss experimental considerations and quality management for implementing clinical tandem mass spectrometry in the clinic with an overview of some key applications.

Innovative Approaches to Assess Intermediate Cardiovascular Risk Subjects: A Review From Clinical to Metabolomics Strategies

Current risk stratification strategies for coronary artery disease (CAD) have low predictive value in asymptomatic subjects classified as intermediate cardiovascular risk. This is relevant because not all coronary events occur in individuals with traditional multiple risk factors. Most importantly, the first manifestation of the disease may be either sudden cardiac death or acute coronary syndrome, after rupture and thrombosis of an unstable non-obstructive atherosclerotic plaque, which was previously silent. The inaccurate stratification using the current models may ultimately subject the individual to excessive or insufficient preventive therapies. A breakthrough in the comprehension of the molecular mechanisms governing the atherosclerosis pathology has driven many researches toward the necessity for a better risk stratification. In this Review, we discuss how metabolomics screening integrated with traditional risk assessments becomes a powerful approach to improve non-invasive CAD subclinical diagnostics. In addition, this Review highlights the findings of metabolomics studies performed by two relevant analytical platforms in current use-mass spectrometry (MS) hyphenated to separation techniques and nuclear magnetic resonance spectroscopy (NMR) -and evaluates critically the challenges for further clinical implementation of metabolomics data. We also discuss the modern understanding of the pathophysiology of atherosclerosis and the limitations of traditional analytical methods. Our aim is to show how discriminant metabolites originated from metabolomics approaches may become promising candidate molecules to aid intermediate risk patient stratification for cardiovascular events and how these tools could successfully meet the demands to translate cardiovascular metabolic biomarkers into clinical settings.

Gas Chromatography-Mass Spectroscopy-Based Metabolomics Analysis Reveals Potential Biochemical Markers for Diagnosis of Gestational Diabetes Mellitus

Due to many adverse effects of gestational diabetes mellitus (GDM) on the mother and fetus, its diagnosis is crucial. The presence of GDM can be confirmed by an abnormal fasting plasma glucose level (aFPG) and/or oral glucose tolerance test (OGTT) performed mostly between 24 and 28 gestational week. Both aFPG and abnormal glucose tolerance (aGT) are used to diagnose GDM. In comparison to measurement of FPG, OGTT is time-consuming, usually inconvenient for the patient, and very often needs to be repeated. Therefore, it is necessary to seek tests that will be helpful and convenient to diagnose GDM. For this reason, we investigated the differences in fasting serum metabolites between GDM women with abnGM and normal FPG (aGT-GDM group), with aFPG and normal glucose metabolism (aFPG-GDM group) as well as pregnant women with normal glucose tolerance (NGT) being a control group. Serum metabolites were measured by an untargeted approach using gas chromatography–mass spectrometry (GC–MS). In the discovery phase, fasting serum samples collected from 79 pregnant women (aFPG-GDM, n = 24; aGT-GDM, n = 26; NGT, n = 29) between 24 and 28 weeks of gestation (gwk) were fingerprinted. A set of metabolites (α–hydroxybutyric acid (α–HB), β–hydroxybutyric acid (β–HB), and several fatty acids) significant in aGT-GDM vs NGT but not significant in aFPG-GDM vs NGT comparison in the discovery phase was selected for validation. These metabolites were quantified by a targeted GC–MS method in a validation cohort consisted of 163 pregnant women (aFPG-GDM, n = 51; aGT-GDM, n = 44; and NGT, n = 68). Targeted analyses were also performed on the serum collected from 92 healthy women in the first trimester (8–14 gwk) who were NGT at this time, but in the second trimester (24–28 gwk) they were diagnosed with GDM. It was found that α–HB, β–HB, and several fatty acids were associated with aGT-GDM. A combination of α–HB, β–HB, and myristic acid was found highly specific and sensitive for the diagnosis of GDM manifested by aGT-GDM (AUC = 0.828) or to select women at a risk of aGT-GDM in the first trimester (AUC = 0.791). Our findings provide new potential markers of GDM and may have implications for its early diagnosis.

Society for Endocrinology UK Guidance on the initial evaluation of a suspected difference or disorder of sex development (Revised 2021)

It is paramount that any child or adolescent with a suspected difference or disorder of sex development (DSD) is assessed by an experienced clinician with adequate knowledge about the range of conditions associated with DSD and is discussed with the regional DSD service. In most cases, the paediatric endocrinologist within this service acts as the first point of contact but involvement of the regional multidisciplinary service will also ensure prompt access to specialist psychology and nursing care. The underlying pathophysiology of DSD and the process of delineating this should be discussed with the parents and affected young person with all diagnostic tests undertaken in a timely fashion. Finally, for rare conditions such as these, it is imperative that clinical experience is shared through national and international clinical and research collaborations.

Peptide Charge Derivatization as a Tool for Early Detection of Preeclampsia by Mass Spectrometry-A Comparison with the ELISA Test

Early detection of any preeclampsia biomarkers may lower the risk of mortality, both for a mother and a child. Our study focuses on techniques for preeclampsia biomarker identification by comparing the results of a method using liquid chromatography mass spectrometry in multiple reaction monitoring mode (LC-MS/MS) with those by the enzyme-linked immunosorbent assay (ELISA) test, as well as by comparing the obtained results with clinical data. In the proposed LC-MS/MS method a tryptic digest peptide charge derivatization strategy was used as a tool for sensitive detection of podocin, i.e., a previously discovered preeclampsia biomarker present in urine samples from pregnant women. Urine samples from pregnant women with diagnosed preeclampsia were collected at different stages of pregnancy and from healthy subjects, and then were analyzed by ELISA test and the proposed method with LC-MS/MS. Charge derivatization of the ε amino group of C-terminal lysine residues in tryptic digests by 2,4,6-triphenylpyrylium salt was performed to increase the ionization efficiency in the LC-MS/MS mode. Podocin was identified at the early stage of pregnancy, while its detection using an ELISA test was not possible. The protocol for urine sample preparation was optimized. Our results show that the proposed method by LC-MS/MS in combination with peptide charge derivatization, provides an ultrasensitive tool for diagnosis of preeclampsia, and provides earlier detection than a clinical diagnosis or ELISA test. The proposed solution may revolutionize medical diagnostics.

Practical aspect of dimer adduct formation in small-molecule drug analysis with LC-MS/MS

Aim: Since the MS/MS based detection of small-molecule drugs with poor or even no ion fragmentation is a challenge in bioanalysis, alternative MS/MS detection strategies were in focus of this study and applied in the field of forensic toxicology. Material & methods: Analyte quantification with liquid chromatography-tandem mass spectrometry of problematic drugs was studied by the application of dimer adduct formation and valproic acid (VPA) was used as a model drug. VPA adduct ions could be identified during infusion experiments and the VPA dimer adduct ion was optimized for the detection. Conclusion: Dimer adduct ion formation can be used as an effective way of VPA quantification in human serum. Further, the parallel detection of dimer adduct ions with other adduct ion types can be stated as advantage in LC-MS/MS analysis of problematic drugs.

Arginine, as a Key Indicator for Real-Time Stability Monitoring of Quality Control in the Newborn Screening Test Using Dried Blood Spot

Dried blood spots (DBS) have advantages such as minimizing blood collection volume and the distress to neonate. DBS have been used for tandem mass spectrometry (MS/MS)-based newborn screening tests (NST) of amino acid (AA) and acylcarnitine. The Newborn Screening Quality Assurance Program (NSQAP) have been provided quality control (QC) materials for MS/MS, as DBS cards. The NSQAP is generally provided within 14 months of the shelf life and the recommended storage condition is at −10 °C to −30 °C. Previously, several accelerated degradation studies had been performed to determine the transportation stability and short-term stability of AAs and acylcarnitines in DBS. However, the experimental condition is markedly different to the storage condition. We performed long-term monitoring for the real-time stability of seven AAs and 14 acylcarnitines from three levels of 2012 NSQAP QC materials across a time period of 788 days. Arginine suddenly yielded a catastrophic degeneration pattern, which started around D300. When comparing this with previous accelerated degradation studies, methionine, tyrosine, citrulline, and acetylcarnitine did not show a remarkable measurand drift for the real-time stability, except for arginine. Our study showed that arginine would require intensive QC monitoring in routine practice, and should be used for the assessment of the stability in long-term storage of DBS samples for biobanking.

Integrated Proteotranscriptomics of Human Myometrium in Labor Landscape Reveals the Increased Molecular Associated With Inflammation Under Hypoxia Stress

During labor, a variety of coordinated physiological and biochemical events cause the myometrium to transition from a quiescent to contractile state; the molecular mechanisms responsible for this transition, however, remain unclear. To better understand this transition at a molecular level, the global transcriptome and proteome of human myometrial samples in labor and those not in labor were investigated through RNA sequencing (RNA-seq) and quantitative liquid chromatography–tandem mass spectrometry (LC-MS/MS) via data-independent acquisition (DIA) and parallel reaction monitoring (PRM) methods. Furthermore, an integrated proteotranscriptomic analysis was performed to explore biological processes and pathway alterations during labor; this analysis identified 1,626 differentially expressed mRNAs (1,101 upregulated, 525 downregulated) and 135 differentially expressed proteins (97 upregulated, 38 downregulated) in myometrium between nonlabor and in labor groups. The comprehensive results of these analyses showed that the upregulated mRNAs and proteins increased inflammation under hypoxia stress in the myometrium under labor, and related proteins and cytokines were validated by PRM and Luminex assays. Our study confirmed the biological process of inflammation and hypoxia in laboring myometrium at the transcriptome and proteome levels and provided recourse to discover new molecular and biological changes during labor.

Finger sweat analysis enables short interval metabolic biomonitoring in humans

Metabolic biomonitoring in humans is typically based on the sampling of blood, plasma or urine. Although established in the clinical routine, these sampling procedures are often associated with a variety of compliance issues, which are impeding time-course studies. Here, we show that the metabolic profiling of the minute amounts of sweat sampled from fingertips addresses this challenge. Sweat sampling from fingertips is non-invasive, robust and can be accomplished repeatedly by untrained personnel. The sweat matrix represents a rich source for metabolic phenotyping. We confirm the feasibility of short interval sampling of sweat from the fingertips in time-course studies involving the consumption of coffee or the ingestion of a caffeine capsule after a fasting interval, in which we successfully monitor all known caffeine metabolites as well as endogenous metabolic responses. Fluctuations in the rate of sweat production are accounted for by mathematical modelling to reveal individual rates of caffeine uptake, metabolism and clearance. To conclude, metabotyping using sweat from fingertips combined with mathematical network modelling shows promise for broad applications in precision medicine by enabling the assessment of dynamic metabolic patterns, which may overcome the limitations of purely compositional biomarkers.

Overcome Isomer Interference in 1α,25-Dihydroxyvitamin D Quantitation by Liquid Chromatography-Tandem Mass Spectrometry

BACKGROUND

The circulating concentration of 1α,25-dihydroxyvitamin D [1α,25(OH)2D] is very low, and the presence of multiple isomers may lead to inaccurate quantitation if not separated prior to analysis. Antibody-based immunoextraction procedures are sometimes used to remove structurally related isomers of 1α,25(OH)2D prior to an LC-MS/MS analysis. However, immunoextraction increases sample preparation time and cost. In addition, some dihydroxyvitamin D metabolites are not completely removed by immunoextraction.

METHOD

We developed an HPLC method using a phenyl-hexyl column to investigate interfering isomers of 1α,25(OH)2D.

RESULT

Using this method, 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) derivatization product of 1α,25(OH)2D was found to be present as 2 epimers, which were separated chromatographically with an area ratio of 2:1. PTAD derivatized metabolite of 25-hydroxyvitamin D3 [i.e., 4β,25-dihydroxyvitamin D3 (4β,25(OH)2D3)] eluted out between 6R and 6S epimers of derivatized 1α,25(OH)2D3. If not chromatographically resolved, 4β,25(OH)2D can affect 1α,25(OH)2D quantitation. In a method comparison study, it was found that the presence of 4β,25(OH)2D produced positive bias up to 127% on 1α,25(OH)2D3 quantitation.

CONCLUSION

The LC-MS/MS method we developed without an immunoextraction procedure was able to resolve the major interference peak from 1α,25(OH)2D and achieved reliable quantitation of 1α,25(OH)2D.

Fast accurate quantification of salivary cortisol and cortisone in a large-scale clinical stress study by micro-UHPLC-ESI-MS/MS using a surrogate calibrant approach

Cortisol and cortisone are common markers for stress and thus preferentially analyzed in matrices that allow non-invasive sampling such as saliva. Though the major drawback of immunoassays is lack of specificity due to cross reactivities, they are still most commonly used for quantification of steroid hormones. To overcome such problems, sensitive methods based on liquid chromatography-mass spectrometry are becoming more and more accepted as the golden standard for steroid bioanalysis as they achieve accurate quantification at trace levels for multiple analytes in the same run. Along this line, the aim of this study was the development of a new microflow UHPLC-ESI-MS/MS method for the measurement of salivary cortisol and cortisone, which due to its microflow regime provides enhanced sensitivity and is more ecofriendly. The developed method implemented sample preparation by Solid-Phase Extraction (SPE) in a 96-well plate format. Data acquisitions were carried out in MRM (multiple reaction monitoring) mode. The quantitative determination of endogenous compounds in saliva remains a challenge since analyte-free matrix is lacking. Hence, a surrogate calibrant approach with cortisol-d₄ andcortisone-¹³C₃ was applied for the target compounds in the presented method. A number of factors were optimized and the method validated. The lower limit of quantitation (LLOQ) was 72 and 62 pg mL^-1for cortisol and cortisone, respectively. Linear calibration was achieved in the range from 0.062 to 75.5 ng mL^-1for cortisol-d₄ and 0.072 to 44 ng mL^-1forcortisone-¹³C₃. The performance of the method was also evaluated via proficiency test for salivary cortisol. Finally, it was applied successfully to evaluate cortisol and cortisone concentrations in multiple batches in routine clinical stress study samples (4056 total injections with 1983 study samples). Moreover, the instrument performance (in particular retention time variability) within each batch, between different batches and lot-to-lot of 5 investigated capillary columns over time is described. The work documents that micro-UHPLC-ESI-MS/MS is suitable and robust enough to carry out a full clinical study with greater than 1000s of samples over an extended period if adequate internal standards can be used.

Development of a sensitive liquid chromatography-tandem mass spectrometry method for quantification of human plasma arginine vasopressin

BACKGROUND AND AIMS

Direct measurement of arginine vasopressin (AVP) via immunoassays is not widely conducted, mainly because of technical constraints. Liquid chromatography-tandem mass spectrometry (LC/MS/MS) has been widely used as the gold standard in clinical chemistry. Here, we aimed to develop an MS-based assay to determine human plasma AVP and compare the results with those obtained using a conventional immunoassay.

MATERIALS AND METHODS

We developed a protocol using triple quadrupole MS coupled with LC for the measurement of human plasma AVP. Analytical evaluations of the method were performed, and the results obtained using LC/MS/MS and radioimmunoassay (RIA) were compared.

RESULTS

The lower limit of quantification (LLOQ) for plasma AVP obtained using LC/MS/MS and RIA were 0.2 and 0.4 pg/mL, respectively. Although there was a weak overall correlation between the results obtained using the two different methods, the RIA results did not agree with the LC/MS/MS results, particularly at low concentrations.

CONCLUSIONS

AVP detection through RIA is not satisfactory compared with that using LC/MS/MS. Diagnostic values of direct AVP measurements must be evaluated based on the results obtained via sensitive and accurate MS-based methods rather than those obtained through RIA.

Nasopharyngeal metabolomics and machine learning approach for the diagnosis of influenza

Background

Respiratory virus infections are significant causes of morbidity and mortality, and may induce host metabolite alterations by infecting respiratory epithelial cells. We investigated the use of liquid chromatography quadrupole time-of-flight mass spectrometry (LC/Q-TOF) combined with machine learning for the diagnosis of influenza infection.

Methods

We analyzed nasopharyngeal swab samples by LC/Q-TOF to identify distinct metabolic signatures for diagnosis of acute illness. Machine learning models were performed for classification, followed by Shapley additive explanation (SHAP) analysis to analyze feature importance and for biomarker discovery.

Findings

A total of 236 samples were tested in the discovery phase by LC/Q-TOF, including 118 positive samples (40 influenza A 2009 H1N1, 39 influenza H3 and 39 influenza B) as well as 118 age and sex-matched negative controls with acute respiratory illness. Analysis showed an area under the receiver operating characteristic curve (AUC) of 1.00 (95% confidence interval [95% CI] 0.99, 1.00), sensitivity of 1.00 (95% CI 0.86, 1.00) and specificity of 0.96 (95% CI 0.81, 0.99). The metabolite most strongly associated with differential classification was pyroglutamic acid. Independent validation of a biomarker signature based on the top 20 differentiating ion features was performed in a prospective cohort of 96 symptomatic individuals including 48 positive samples (24 influenza A 2009 H1N1, 5 influenza H3 and 19 influenza B) and 48 negative samples. Testing performed using a clinically-applicable targeted approach, liquid chromatography triple quadrupole mass spectrometry, showed an AUC of 1.00 (95% CI 0.998, 1.00), sensitivity of 0.94 (95% CI 0.83, 0.98), and specificity of 1.00 (95% CI 0.93, 1.00). Limitations include lack of sample suitability assessment, and need to validate these findings in additional patient populations.

Interpretation

This metabolomic approach has potential for diagnostic applications in infectious diseases testing, including other respiratory viruses, and may eventually be adapted for point-of-care testing.

Mass spectrometry based high-throughput bioanalysis of low molecular weight compounds: are we ready to support personalized medicine?

Liquid chromatography coupled to mass spectrometry (LC-MS) is the gold standard in bioanalysis for the development of quantitative assays to support drug development or therapeutic drug monitoring. High-throughput and low-cost gene sequencing have enabled a paradigm shift from one treatment fits all to personalized medicine (PM). However, gene monitoring provides only partial information about the health state. The full picture requires the combination of gene monitoring with the screening of exogenous compounds, metabolites, lipids, and proteins. This critical review discusses how mass spectrometry–based technologies and approaches including separation sciences, ambient ionization, and ion mobility are/could be used to support high-throughput bioanalysis of endogenous end exogenous low molecular weight compounds. It includes also various biological sample types (from blood to expired air), and various sample preparation techniques.

Alternative detection of SARS-CoV-2 RNA by a new assay based on mass spectrometry

OBJECTIVES

Accurate detection of SARS-CoV-2 RNA is essential to stopping the spread of SARS-CoV-2. The aim of this study was to evaluate the performance of the recently introduced MassARRAY^® SARS-CoV-2 Panel and to compare it to the cobas^® SARS-CoV-2 Test.

METHODS

The MassARRAY^® SARS-CoV-2 Panel consists of five assays targeting different sequences of the SARS-CoV-2 genome. Accuracy was determined using national and international proficiency panels including 27 samples. For clinical evaluation, 101 residual clinical samples were analyzed and results compared. Samples had been tested for SARS-CoV-2 RNA with the cobas^® SARS-CoV-2 Test.

RESULTS

When accuracy was tested with the MassARRAY^® SARS-CoV-2 Panel, 25 of 27 (92.6%) samples revealed correct results. When clinical samples were analyzed with the MassARRAY^® SARS-CoV-2 Panel and compared to the cobas^® SARS-CoV-2 Test, 100 samples showed concordant results. One sample was found to be inconclusive with the MassARRAY^® SARS-CoV-2 Panel. When time-to-results were compared, the new assay showed longer total and hands-on times.

CONCLUSIONS

The MassARRAY^® SARS-CoV-2 Panel showed a good performance and proved to be suitable for use in the routine diagnostic laboratory. Especially during phases of shortage of reagents and/or disposables, the new test system appears as beneficial alternative to standard assays used for detection of SARS-CoV-2 RNA.

Quantification of SARS-CoV-2 spike and nucleocapsid proteins using isotope dilution tandem mass spectrometry

The emergence and subsequent global outbreak of the novel coronavirus SARS-CoV-2 prompted our laboratory to launch efforts to develop methods for SARS-CoV-2 antigen detection and quantification. We present an isotope dilution mass spectrometry method (IDMS) for rapid and accurate quantification of the primary antigens, spike and nucleocapsid proteins. This IDMS method utilizes liquid chromatography-tandem mass spectrometry (LC-MS/MS) to analyze sample tryptic digests for detection and quantification of selected conserved peptides of SARS-CoV-2 spike and nucleocapsid proteins. The IDMS method has the necessary attributes to be successfully utilized for accurate quantification in SARS-CoV-2 protein-based vaccines and as targets of rapid diagnostic tests. Absolute quantification was achieved by quantifying and averaging 5 peptides for spike protein (3 peptides in the S1 subunit and 2 peptides in the S2 subunit) and 4 peptides for nucleocapsid protein. The overall relative standard deviation of the method was 3.67% for spike protein and 5.11% for nucleocapsid protein. IDMS offers speed (5 h total analysis time), sensitivity (LOQ; 10 fmol/µL) and precision for quantification of SARS-CoV-2 spike and nucleocapsid proteins.

Understanding Cervical Cancer through Proteomics

Cancer is one of the leading public health issues worldwide, and the number of cancer patients increases every day. Particularly, cervical cancer (CC) is still the second leading cause of cancer death in women from developing countries. Thus, it is essential to deepen our knowledge about the molecular pathogenesis of CC and propose new therapeutic targets and new methods to diagnose this disease in its early stages. Differential expression analysis using high-throughput techniques applied to biological samples allows determining the physiological state of normal cells and the changes produced by cancer development. The cluster of differential molecular profiles in the genome, the transcriptome, or the proteome is analyzed in the disease, and it is called the molecular signature of cancer. Proteomic analysis of biological samples of patients with different grades of cervical intraepithelial neoplasia (CIN) and CC has served to elucidate the pathways involved in the development and progression of cancer and identify cervical proteins associated with CC. However, several cervical carcinogenesis mechanisms are still unclear. Detecting pathologies in their earliest stages can significantly improve a patient's survival rate, prognosis, and recurrence. The present review is an update on the proteomic study of CC.

The Role of Non-Enzymatic Degradation of Meropenem-Insights from the Bottle to the Body

Several studies have addressed the poor stability of meropenem in aqueous solutions, though not considering the main degradation product, the open-ring metabolite (ORM) form. In the present work, we elucidate the metabolic fate of meropenem and ORM from continuous infusion to the human bloodstream. We performed in vitro infusate stability tests at ambient temperature with 2% meropenem reconstituted in 0.9% normal saline, and body temperature warmed buffered human serum with 2, 10, and 50 mg/L meropenem, covering the therapeutic range. We also examined meropenem and ORM levels over several days in six critically ill patients receiving continuous infusions. Meropenem exhibited a constant degradation rate of 0.006/h and 0.025/h in normal saline at 22 °C and serum at 37 °C, respectively. Given that 2% meropenem remains stable for 17.5 h in normal saline (≥90% of the initial concentration), we recommend replacement of the infusate every 12 h. Our patients showed inter-individually highly variable, but intra-individually constant molar ORM/(meropenem + ORM) ratios of 0.21–0.52. Applying a population pharmacokinetic approach using the degradation rate in serum, spontaneous degradation accounted for only 6% of the total clearance.

Sample Preparation Strategies for Antibody-Free Quantitative Analysis of High Mobility Group Box 1 Protein

Sickness behavior and fatigue are induced by cerebral mechanisms involving inflammatory cytokines. High mobility group box 1 (HMGB1) is an alarmin, and a potential key player in this process. Reliable quantification methods for total HMGB1 and its redox variants must be established in order to clearly understand how it functions. Current methods pose significant challenges due to interference from other plasma proteins and autoantibodies. We aimed to develop an antibody-free sample preparation method followed by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) to measure HMGB1 in human plasma. Different methods were applied for the removal of interfering proteins and the enrichment of HMGB1 from spiked human plasma samples. A comparison of methods showed an overall low extraction recovery (<40%), probably due to the stickiness of HMGB1. Reversed-phase liquid chromatography separation of intact proteins in diluted plasma yielded the most promising results. The method produced an even higher degree of HMGB1 purification than that observed with immunoaffinity extraction. Detection sensitivity needs to be further improved for the measurement of HMGB1 in patient samples. Nevertheless, it has been demonstrated that a versatile and fully antibody-free sample preparation method is possible, which could be of great use in further investigations.

Breaking Through the Barrier: Regulatory Considerations Relevant to Ambient Mass Spectrometry at the Bedside

Rapid characterization of tissue disorder using ambient mass spectrometry (MS) techniques, requiring little to no preanalytical preparations of sampled tissues, has been shown using a variety of ion sources and with many disease classes. A brief overview of ambient MS in clinical applications, the state of the art in regulatory affairs, and recommendations to facilitate adoption for use at the bedside are presented. Unique challenges in the validation of untargeted MS methods and additional safety and compliance requirements for deployment within a clinical setting are further discussed. Development of a harmonized validation strategy for ambient MS methods is emphasized.

Design of experiments for development and optimization of a liquid chromatography coupled to tandem mass spectrometry bioanalytical assay

Design of experiments (DoE) is a valuable tool for the optimization of quantitative bioanalytical methods utilizing liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Liquid chromatography mass spectrometry (LC-MS) is composed of several processes, including, liquid introduction and analyte ionization. The goal is to transfer analytes from atmospheric pressure to vacuum and maintain conditions that are compatible for both LC and MS. These processes involve many experimental factors which need to be simultaneously optimized to obtain maximum sensitivity and resolution at minimum retention time. In this tutorial, the basic concepts of DoE will be explained with focus on practical use of DoE. Three case studies optimized with DoE for liquid chromatography tandem mass spectrometry (LC-MS/MS) quantitative assays will then be presented.

Targeted Metabolomics as a Tool in Discriminating Endocrine From Primary Hypertension

CONTEXT

Identification of patients with endocrine forms of hypertension (EHT) (primary hyperaldosteronism [PA], pheochromocytoma/paraganglioma [PPGL], and Cushing syndrome [CS]) provides the basis to implement individualized therapeutic strategies. Targeted metabolomics (TM) have revealed promising results in profiling cardiovascular diseases and endocrine conditions associated with hypertension.

OBJECTIVE

Use TM to identify distinct metabolic patterns between primary hypertension (PHT) and EHT and test its discriminating ability.

METHODS

Retrospective analyses of PHT and EHT patients from a European multicenter study (ENSAT-HT). TM was performed on stored blood samples using liquid chromatography mass spectrometry. To identify discriminating metabolites a "classical approach" (CA) (performing a series of univariate and multivariate analyses) and a "machine learning approach" (MLA) (using random forest) were used.The study included 282 adult patients (52% female; mean age 49 years) with proven PHT (n = 59) and EHT (n = 223 with 40 CS, 107 PA, and 76 PPGL), respectively.

RESULTS

From 155 metabolites eligible for statistical analyses, 31 were identified discriminating between PHT and EHT using the CA and 27 using the MLA, of which 16 metabolites (C9, C16, C16:1, C18:1, C18:2, arginine, aspartate, glutamate, ornithine, spermidine, lysoPCaC16:0, lysoPCaC20:4, lysoPCaC24:0, PCaeC42:0, SM C18:1, SM C20:2) were found by both approaches. The receiver operating characteristic curve built on the top 15 metabolites from the CA provided an area under the curve (AUC) of 0.86, which was similar to the performance of the 15 metabolites from MLA (AUC 0.83).

CONCLUSION

TM identifies distinct metabolic pattern between PHT and EHT providing promising discriminating performance.