Blood microsampling technologies: Innovations and applications in 2022

Investigator-Initiated Clinical Pharmacokinetic Studies in Resource-Limited Settings: Minimal Requirements and Practical Guidance

Clinical pharmacology studies are critical for determining the efficacy and safety of drugs. Due to the resource-intensive nature of these studies, most have been conducted in high-income countries, leading to a significant gap in clinical pharmacology data for patients in low- and middle-income countries. This paper provides an overview of the minimal requirements for performing a clinical pharmacology investigator-initiated trial (IIT), including pharmacokinetic sampling. We identify common challenges in resource-limited settings and propose strategies to overcome them. This guideline covers regulatory approval, participant recruitment, drug storage, sample collection and handling, transport, bioanalytical analysis, and data management tailored to the constraints of resource-limited settings. Strategies are proposed to minimize resource demands, including simplified study designs, the use of technologies like whole blood microsampling, and opportunities for collaboration. The goal is to provide practical guidance for those seeking to perform a clinical pharmacology IIT in resource-limited settings to improve safe and effective drug treatment for patients worldwide. Beyond the scope of this guideline is a detailed step-by-step guide on how to perform clinical pharmacology studies.

Assessment and cross-validation of calibration transferability between dried blood spot sampling devices for accurate quantification of phosphatidylethanol

Phosphatidylethanol (PEth) is a direct alcohol biomarker which is used in a variety of clinical and forensic contexts. Due to its limited stability in whole blood, PEth is routinely analysed using dried blood spots (DBS). There are many different commercially available sampling systems for DBS, but data on their comparability is scarce. The aim of this study was to develop and validate a LC-MS/MS method for the quantification of PEth 16:0/18:1 and PEth 16:0/18:2 for three different DBS sampling systems: Whatman™ filter paper (903 Protein Saver Cards), Mitra® and Capitainer®B Vanadate. The transferability of calibration curves and their applicability across these devices should be assessed. The results showed that DBS of all devices could be prepared and analysed using the same procedure. Validation was successful for the devices. The accuracy of QCs was best if quantified using the matching DBS sampling device calibration curve (bias < 15 %). Higher, but still acceptable, bias values were observed when using a Whatman™ calibration curve to quantify PEth in DBS of the Capitainer®B Vanadate system and vice versa. Mitra® QCs should only be quantified using device-specific calibration curves, as in all other cases, accuracy exceeded the limit of 15 %. We recommend analysing samples using device-specific calibrations at all times, as determined PEth concentrations might be crucial for patients and should not be subjected to any avoidable uncertainty.

Lipidome plasticity in medium- and long-chain fatty acid oxidation disorders: Insights from dried blood spot lipidomics

Fatty acid (FA) oxidation disorders (FAOD) are characterized by accumulation of specific acylcarnitines (CAR) and FA and can lead to potentially severe complications. In this study, dried blood spots (DBS) combined with LC-MS lipidomics analysis were used to assess lipidome plasticity in medium-chain acyl-CoA dehydrogenase deficiency (MCADD), long-chain hydroxyacyl-CoA dehydrogenase deficiency (LCHADD), and very long-chain acyl-CoA dehydrogenase deficiency (VLCADD), compared to control (CT) individuals, for screening potential prognostic biomarkers. Statistically significant variations were found in CAR, biomarkers for FAOD diagnosis, but other lipid species showed variations depending on the FAOD. Common changes in all FAOD included a few phosphatidylcholine (PC) lipid species, notably an up-regulation of LPC 16:1, possibly associated with a higher risk of cardiovascular disease (CVD). In LCHADD and VLCADD, an up-regulation of odd-chain PC (PC 33:0, PC 35:4 and PC 37:4) was observed. VLCADD exhibited higher levels of odd-chain TG, while LCHADD showed an up-regulation of ceramide (Cer 41:2;O2). The increase in the Cer class has been found to be associated with neurodegeneration and may contribute to the risk of developing this condition in LCHADD. An upregulation of ether-linked PC lipid species, including plasmenyl (known as endogenous antioxidants), was observed in MCADD, possibly as a response to increased oxidative stress reported in this disorder. Overall, DBS combined with lipidomics effectively pinpoints the lipid plasticity in FAOD, highlighting potential specific biomarkers for disease prognosis that warrant further validation for their association with the development of FAOD comorbidities.

Validation of a Reusable, Thermally Protective Specimen Shipper for Decentralized Sample Collections

BACKGROUND

The proliferation of decentralized sample collection models improves patient access and experience with laboratory medicine. However, many analytes have limited stability in liquid whole blood, serum, or plasma such that prompt transport under controlled temperature protection is crucial to analytical accuracy. Here we validate the Labcorp TrueTherm™ reusable shipper intended to thermally protect small volume specimens.

METHODS

Various TrueTherm shipper models were configured using stainless steel vacuum bottles, rigid phase change material (PCM) packs, and foam stoppers. A series of bench and real-world trans-US shipping studies were performed to evaluate thermal endurance against frozen, refrigerated, room temperature, and incubated temperature allowance criteria under summer and winter exposure conditions. Analytical utility was assessed by measuring 25 serum-based clinical chemistry markers using Roche cobas® 8000 analyzers following shipment in microvolume containers centrifuged or uncentrifuged and using various shipping methods. Additional studies evaluated the effect of centrifugation and thermal exposures on specimens exposed to ISTA-7D summer and winter shipping profiles.

RESULTS

The TrueTherm shipper exceeded 72-hour thermal endurance for most targeted applications when subjected to standard shipping validation thermal profiles. In real-world shipping studies, TrueTherm shippers paired with sample centrifugation prior to transport enabled most chemistry analytes to be measured with pair-wise comparisons within 2024 CLIA acceptance limits. Microsample hemolysis measurements showed that without centrifugation and thermal protection, average hemolysis levels fell well above maximum-allowable thresholds for laboratory analyzers.

CONCLUSION

The TrueTherm shipper provides a simple, effective, and reusable method for ensuring thermally protected shipment of small volume samples into centralized laboratories.

A Liquid Chromatography-Tandem Mass Spectrometry Method for the Quantification of Cystic Fibrosis Drugs (Caftors) in Plasma and Its Application for Therapeutic Monitoring

Cystic fibrosis (CF) is a life-threatening disorder caused by mutations in the CFTR gene, leading to defective chloride ion transport and thickened mucus in the respiratory and gastrointestinal systems. CFTR modulators, including ivacaftor, lumacaftor, tezacaftor, and elexacaftor, have improved patient outcomes, but interindividual pharmacokinetic variability and potential drug-drug interactions require therapeutic drug monitoring (TDM) for optimal efficacy and safety. In this context, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method has been developed and validated for the simultaneous quantification of CFTR modulators and their major active metabolites in human plasma to support pharmacokinetic studies and routine TDM. The multiplex LC-MS/MS assay was established using plasma protein precipitation, followed by chromatographic separation on an Xselect HSS T3 (Waters®) column and positive electrospray ionization mode detection. The method was validated based on FDA and EMA guidelines for specificity, linearity, accuracy (89.8-107.8%), repeatability (1.1-8.1%), intermediate fidelity (1.3-10.9%), matrix effects, and stability, demonstrating a robust performance with excellent precision and accuracy. International interlaboratory comparisons confirmed the reliability of the assay. The developed method can be applied for the clinical monitoring of caftors' plasma concentrations and preliminary data suggest that it can also be applied to alternative matrices, such as breast milk. This method will serve to characterize caftors' pharmacokinetic variability and monitor drug-drug interactions to further refine personalized dosing strategies and enhance precision medicine treatments for patients with CF.

Dried Spot Paradigm: Problems and Prospects in Proteomics

The analysis of biological fluids plays a crucial role in biomarker discovery, disease diagnostics, and precision medicine. Dried sample carriers-such as dried blood spots, dried plasma, serum, saliva, tears, and urine-have emerged as powerful tools, offering advantages in sample collection, storage, and transport, particularly in remote and resource-limited settings. Recent advances in proteomic methodologies have expanded the potential of these dried matrices, yet challenges related to protein stability, sensitivity, and standardization persist. This review critically examines the current state of proteomic investigations using dried biological fluids. Furthermore, we compare proteomics' progress in this field with other omics approaches, such as metabolomics, to contextualize its development and integration potential. While dried fluid proteomics is promising for non-invasive diagnostics and large-scale epidemiological studies, addressing technical limitations will be essential for its broader adoption in clinical and translational research.

Dried Blood Spots to Assess Cardiovascular-Kidney-Metabolic Health

Dried blood spot sampling offers a scalable strategy to close diagnostic gaps and improve global surveillance for cardiovascular-kidney-metabolic syndrome. However, assay performance and the extent of validity vary widely between biomarkers used in cardiovascular-kidney-metabolic health assessment under different settings and have not been well described. To fill this gap, we conducted a systematic search of the literature and a narrative synthesis through April 2024 and included reports with laboratory or field validation measuring biomarkers that can be used in cardiovascular-kidney-metabolic health assessment. We categorized assays into categories based on laboratory validation: excellent performance (r>0.95 with gold standard methods and coefficients of variation <5%), very good performance (r>0.90 and coefficients of variation <10%), reasonable performance (r>0.80 and coefficients of variation <15%), and poor performance (r<0.80 or coefficients of variation >15%). The extent of validation was determined by the total number of field validation studies with strong agreement. Hemoglobin A1c has strong laboratory and field validation and should be considered for expansion into clinical testing in low-resource settings. Traditional lipid biomarkers showed poor performance in field validation studies, but apoB (apolipoprotein B), creatinine, cystatin C, and NT-proBNP (N-terminal prohormone of brain natriuretic peptide) showed promising initial laboratory validation results and deserve greater attention in field validation studies. High-sensitivity C-reactive protein has strong laboratory and field validation but has limited clinical utility. Dried blood spot assays have been developed for biomarkers that offer mechanistic insights including inflammatory and vascular injury markers, fatty acids, malondialdehyde, asymmetric dimethylarginine, trimethylamine N-oxide, carnitines, and omics.

Rapid determination of phenylalanine and tyrosine in volumetrically collected dried blood spots using fully automated processing and analysis by capillary electrophoresis

An off-the-shelf Agilent 7100 capillary electrophoresis (CE) instrument was employed for the automated processing and analysis of dried blood spots (DBSs) collected by Capitainer®B volumetric devices. Solutions for DBS elutions were transferred directly into CE vials through a separation capillary by the application of an auxiliary nitrogen gas connected to the external pressure line of the CE instrument. This allowed for liquid handling at pressures up to 15 bar and enabled the use of a single capillary for rapid DBS processing and efficient CE separations. The resulting DBS eluates were at-line injected into a short capillary end, which served for improved instrumental simplicity and short CE analysis times. The current set-up necessitated neither hardware nor software adjustments of the CE instrument, except for the connection of a gas cylinder to an in-built connector. The novel features presented in this study (DBSs with exact blood volumes, high external pressures, and short-end injections) were used for the automated determination of clinically relevant markers, phenylalanine (Phe) and tyrosine (Tyr), in DBS samples. Sensitive and selective Phe and Tyr quantification was achieved by CE-UV in 375 mM formic acid and 0.01 % (v/v) Tween 20 (pH 2.09) as a background electrolyte. The total processing and analysis times per one DBS were <1.5 and 4.5 min, respectively, in a sequence of 36 DBSs, and resulted in a sample throughput of >10 DBSs per hour. The intra- and inter-day repeatability values were better than 5.9 and 1.1 % RSD for peak areas and migration times, respectively, and calibration curves were linear in the 20-3000 μM (Phe) and 20-250 μM (Tyr) range (R2 ≥ 0.9973). The limits of detection were ≤2 μM and enabled the determination of endogenous Phe and Tyr concentrations as well as elevated Phe concentrations and Phe/Tyr ratios, which are the typical markers for neonatal phenylketonuria screening.

Quantifying sampling method-induced imprecision in user-friendly lateral upper arm blood collection: Introducing σ3-methodology (S3) for the verification of alternative sampling methods with TAP® II as a use case

BACKGROUND

Alternative means of blood sampling continue to grow due to the scarcity of phlebotomists and the need for person-centered care. It is crucial to consistently support these alternative blood sampling innovations with scientific evidence to guarantee the quality of care, especially when implementing for instance Lateral Upper-arm Blood Collection (LUBC) for use at home. Knowledge gaps remain in how to quantify imprecision introduced by the collection method and its impact on clinical use.

METHODS

We developed the Six Sigma analysis for alternative Sampling methods, including sampling method-induced imprecision, accuracy and precision, called σ3-methodology (S3). We performed a two-step verification using σ3-methodology for LUBC TAP® II, which included fourteen routine clinical analytes. We used venipuncture as the gold standard.

RESULTS

The biggest source of imprecision for all analytes was sampling method-induced imprecision, which, for the first time, was quantified, resulting in a varying effect on the clinical usability. TAP® II showed acceptable analytical performance for ALP, bilirubin, HDL-cholesterol, CRP and sodium. Unacceptable analytical performance was found for ALT, AST, cholesterol, creatinine, GGT, HbA1c, potassium, LDH and triglycerides.

CONCLUSION

Alternative blood sampling innovations hold promise for advancing diagnostic care, aiming to deliver accessible decentralised sample collection at home that does not require phlebotomist involvement. However, sampling method-induced imprecision should not be overlooked in the performance assessment to guarantee responsible development that will contribute to the success and desirable societal impact of alternative sampling technologies.

Microsampling techniques and patient-centric therapeutic drug monitoring of immunosuppressants

Immunosuppressive pharmacotherapy after solid organ transplantation (SOT) requires therapeutic drug monitoring (TDM) for therapy individualization. The venous whole blood is still considered as routine matrix for monitoring immunosuppressive drug concentration. On the other hand, as an alternative, capillary blood collected using noninvasive sampling is convergent with a patient-centric approach. Despite their disadvantages regarding sample homogeneity and the hematocrit effect, well-known dried blood spot techniques have shown promising results. Volumetric absorptive microsampling (VAMS) and quantitative dried blood spot (qDBS) have successfully eliminated these unfavorable biased elements. Microsampling can be used in transplant recipients' care, mainly due to long-term therapy under control drug concentrations and the long distance between the place of the patient's residence and the diagnostic laboratory in the transplant center. The study aimed to discuss the clinical consequences of implementing microsampling techniques for TDM of immunosuppressants. Additionally, we have discussed the 'hot topics' in microsampling: home-based self-sampling, adherence to therapy monitoring, and drug concentration conversion to estimated traditional matrices. Finally, based on our experience and current practice, we propose best practices for microsampling implementation from bench to bedside. Microsampling techniques can potentially revolutionise immunosuppressive pharmacotherapy by enabling patient-centric individualisation in various subpopulations, significantly improving post-transplant care.

LC-MS-Based Global Metabolic Profiles of Alternative Blood Specimens Collected by Microsampling

Blood microsampling (BμS) has recently emerged as an interesting approach in the analysis of endogenous metabolites but also in metabolomics applications. Their non-invasive way of use and the simplified logistics that they offer renders these technologies highly attractive in large-scale studies, especially the novel quantitative microsampling approaches such as VAMs or qDBS. Objectives: Herein, we investigate the potential of BµS devices compared to the conventional plasma samples used in global untargeted mass spectrometry-based metabolomics of blood. Methods: Two novel quantitative devices, namely, Mitra, Capitainer, and the widely used Whatman cards, were selected for comparison with plasma. Venous blood was collected from 10 healthy, overnight-fasted individuals and loaded on the devices; plasma was also collected from the same venous blood. An extraction solvent optimization study was first performed on the three devices before the main study, which compared the global metabolic profiles of the four extracts (three BµS devices and plasma). Analysis was conducted using reverse phase LC-TOF MS in positive mode. Results: BµS devices, especially Mitra and Capitainer, provided equal or even superior information on the metabolic profiling of human blood based on the number and intensity of features and the precision and stability of some annotated metabolites compared to plasma. Despite their rich metabolic profiles, BµS did not capture metabolites associated with biological differentiation of sexes. Conclusions: Overall, our results suggest that a more in-depth investigation of the acquired information is needed for each specific application, as a metabolite-dependent trend was obvious.

Volumetric Absorptive Microsampling in Toxicology

Volumetric absorptive microsampling (VAMS) is an emerging technique in clinical and forensic toxicology. It is recognized as a promising alternative to traditional sampling methods, offering an accurate and minimally invasive means of collecting small volumes of biological samples, such as blood, urine, and saliva. Unlike conventional methods, VAMS provides advantages in terms of sample stability, storage, and transportation, as it enables samples to be collected outside laboratory environments without requiring refrigeration. This review explores several VAMS methodologies, with a particular focus on its application for the quantification of drugs and other substances in clinical and forensic toxicology. It compares VAMS to other microsampling techniques, such as dried blood spots (DBSs), highlighting VAMS's superiority in addressing issues related to sample volume consistency and environmental impact. Despite its advantages, VAMS also presents certain limitations, including higher costs and difficulties in detecting underfilled samples. Overall, VAMS stands out as a microsampling technique with the potential to enhance patient compliance and operational efficiency, positioning itself as a viable tool for toxicological analysis in both clinical and forensic contexts.

Advancements in Mass Spectrometry-Based Targeted Metabolomics and Lipidomics: Implications for Clinical Research

Targeted metabolomics and lipidomics are increasingly utilized in clinical research, providing quantitative and comprehensive assessments of metabolic profiles that underlie physiological and pathological mechanisms. These approaches enable the identification of critical metabolites and metabolic alterations essential for accurate diagnosis and precision treatment. Mass spectrometry, in combination with various separation techniques, offers a highly sensitive and specific platform for implementing targeted metabolomics and lipidomics in clinical settings. Nevertheless, challenges persist in areas such as sample collection, quantification, quality control, and data interpretation. This review summarizes recent advances in targeted metabolomics and lipidomics, emphasizing their applications in clinical research. Advancements, including microsampling, dynamic multiple reaction monitoring, and integration of ion mobility mass spectrometry, are highlighted. Additionally, the review discusses the critical importance of data standardization and harmonization for successful clinical implementation.

Evaluation of low volume sampling devices for a pharmacodynamic biomarker analysis: Challenges and solutions

Low volume sampling technologies have gained popularity as they are minimally invasive, reduce patient burden, enhance population diversity, and have the potential to facilitate decentralized clinical trials. Herein, we validated a Gyrolab assay to measure soluble Mucosal Addressin Cell Adhesion Molecule 1 (sMAdCAM-1) in dried blood samples collected using two low volume sampling devices, Mitra and Tasso-M20. This validated assay was implemented in a proof-of-concept study to compare three low volume sampling devices (Mitra, Tasso-M20 and TassoOne Plus) with serum collected via venipuncture from healthy volunteers receiving etrolizumab. We observed significantly higher concentration of sMAdCAM-1 in dried blood samples collected using Mitra and Tasso-M20 compared to serum in some paired samples, which was attributed to interference from the dried blood extraction buffer. To mitigate this interference, samples required substantial dilution into the appropriate buffer, which negatively impacted the detectability of sMAdCAM-1 with the Gyrolab assay. By employing the Quanterix single molecule array (Simoa), known for its superior assay sensitivity, the interference was minimized in the diluted samples. Both liquid blood collected in TassoOne Plus and dried blood collected using Mitra and Tasso-M20 demonstrated great concordance with serum for sMAdCAM-1 measurement. However, a bias was observed in Mitra dried blood samples, presumably due to the different sample collection sites in comparison with venipuncture and Tasso devices. Our study highlights the potential of low volume sampling technologies for biomarker analysis, and underscores the importance of understanding the challenges and limitations of these technologies before integrating them into clinical studies.

Development and validation of the UHPLC-MS/MS method for the quantitative determination of 25 PFAS in dried blood spots

Per- and polyfluoroalkyl substances (PFAS) are anthropogenic fluorine-containing compounds largely used in industrial and consumer applications. They tend to bioaccumulate in the human body after intake from various sources in daily life. Following repeated exposure to PFAS, a broad range of adverse health outcomes has been reported. Consequently, monitoring PFAS levels in human blood is of paramount importance for public health policies. In contrast with traditional venipuncture, dried blood spots (DBS) constitute a reliable, cheap, and less invasive technique to allow microsampling by capillary blood collected on a specific device. This work aimed to develop and validate an innovative analytical method, combining quantitative DBS with UHPLC-MS/MS instrumentation to identify and quantify 25 PFAS. The extraction procedure was developed and optimized within the range 2-100 ng/mL. Specifically, fortified blood was applied on Capitainer®B devices providing 10 μL of blood volume through a microfluidic channel. After 3 h of drying, the extraction was performed by methanol under sonication, followed by centrifugation. Then, the extraction solvent was evaporated; the residue was reconstituted with the mobile phase solution. The validated method evidenced good sensitivity, with limits of detection ranging from 0.4 ng/mL (PFODA, PFOS) to 1.0 ng/mL (PFOA, 3,6-OPFHpA). The ± 20% acceptability criteria established for intra- and inter-day precision and accuracy were fulfilled for all analytes. High recovery-above 80%-was recorded, whereas significant matrix effect resulted in ion enhancement (> 50%) for 13 analytes. In conclusion, the proposed workflow proved to be reliable, fit for purpose, and easily adaptable in the laboratory routine.

Evaluation of a single Eporatio® micro-dose in urine and dried blood spots

Recombinant human erythropoietin (rhEPO) has been abused as a performance enhancer in sports for several years, but with advancements in detection methods, even micro-doses can be detected in dried blood spot (DBS) samples. Here, we present the results from an Eporatio® (epoetin theta) micro-dose administration study to detect rhEPO in DBS samples. Five healthy male volunteers received a 15 IU/kg subcutaneous dose of Eporatio®. Urine and DBS samples (Mitra® VAMS and Capitainer® B50) were collected 1, 10, 24, 36, 48 and 72 h after drug administration. After 1 h, all urine samples were negative for rhEPO, whereas 40% of DBS samples were considered suspicious. All samples between 10 and 48 h were suspicious for the presence of Eporatio®, except one urine sample that was negative at 48 h. After 72 h, 40% of urine samples and 60% of DBS samples were suspicious and would have proceeded to a confirmation analysis. DBS is an efficient complementary matrix to urine for detection of rhEPO micro-doses.

Antibiotic dose optimisation in the critically ill: targets, evidence and future strategies

PURPOSE OF REVIEW

To highlight the recent evidence for antibiotic pharmacokinetics and pharmacodynamics (PK/PD) in enhancing patient outcomes in sepsis and septic shock. We also summarise the limitations of available data and describe future directions for research to support translation of antibiotic dose optimisation to the clinical setting.

RECENT FINDINGS

Sepsis and septic shock are associated with poor outcomes and require antibiotic dose optimisation, mostly due to significantly altered pharmacokinetics. Many studies, including some randomised controlled trials have been conducted to measure the clinical outcome effects of antibiotic dose optimisation interventions including use of therapeutic drug monitoring. Current data support antibiotic dose optimisation for the critically ill. Further investigation is required to evolve more timely and robust precision antibiotic dose optimisation approaches, and to clearly quantify whether any clinical and health-economic benefits support expanded use of this treatment intervention.

SUMMARY

Antibiotic dose optimisation appears to improve outcomes in critically ill patients with sepsis and septic shock, however further research is required to quantify the level of benefit and develop a stronger knowledge of the role of new technologies to facilitate optimised dosing.

Development of LC-MS/MS method for quantification of Lurasidone using volumetric absorptive microsampling (VAMS); a comparative study between dried blood and plasma samples

The ecological impact of biological, chemical, and analytical research practices, including toxic reagents and biohazardous waste, has led to the development of alternative sampling and extraction techniques for bioanalysis. Microsampling (sample volume < 50 µL) aligns with the 3Rs principle, allowing multiple sampling points from the same animal at different time points and improving animal welfare. A bioanalytical method was developed to investigate factors related to bioanalytical challenges and the implementation of microsampling techniques. An LC-MS/MS method for Volumetric Absorptive Microsampling (VAMS), 20 µL, was developed for quantifying Lurasidone using a liquid-liquid extraction technique. The method uses a C18, Phenomenex column for chromatographic separation and a mobile phase composition of Methanol, Acetonitrile, and Water with 0.1 % HFBA. The method was validated over a concentration range of 5.0 to 1200.0 ng/mL and achieved acceptable precision and accuracy. The recovery for analyte from VAMS was approximately 40% at four different concentrations and is consistent (%CV < 15), with no significant differences among HCT levels. The matrix factor ranged between 85.00 and 115.00 %, showing no substantial issues with reduced or enhanced signal. The stability data showed no significant degradation of LUR in VAMS samples when stored at room temperature for 15 days. The newly established method for Lurasidone confirmed the use of VAMS sampling method and its analysis on LC-MS/MS. Further, the data obtained from microsampling techniques was compared with conventional (plasma) technique, as proof-of-concept, and it confirms the agreement between the two methods. The study supports the advantages of microsampling in protecting the environment and animals while maintaining scientific judgement.

Assessment of Dried Serum Spots (DSS) and Volumetric-Absorptive Microsampling (VAMS) Techniques in Therapeutic Drug Monitoring of (Val)Ganciclovir-Comparative Study in Analytical and Clinical Practice

Ganciclovir (GCV) and its prodrug valganciclovir (VGCV) are antiviral medications primarily used to treat infections caused by cytomegalovirus (CMV), particularly in immunocompromised individuals such as solid organ transplant (SOT) recipients. Therapy with GCV is associated with significant side effects, including bone marrow suppression. Therefore, therapeutic drug monitoring (TDM) is mandatory for an appropriate balance between subtherapeutic and toxic drug levels. This study aimed to develop and validate three novel methods based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) for GCV determination in serum (reference methodology), dried serum spots (DSS), and VAMS-Mitra™ devices. The methods were optimized and validated in the 0.1-25 mg/L calibration range. The obtained results fulfilled the EMA acceptance criteria for bioanalytical method validation. Assessment of DSS and VAMS techniques extended GCV stability to serum for up to a minimum of 49 days (at room temperature, with desiccant). Developed methods were effectively evaluated using 80 clinical serum samples from pediatric renal transplant recipients. Obtained samples were used for DSS, and dried serum VAMS samples were manually generated in the laboratory. The results of GCV determination using serum-, DSS- and VAMS-LC-MS/MS methods were compared using regression analysis and bias evaluation. The conducted statistical analysis confirmed the interchangeability between developed assays. The DSS and VAMS samples are more accessible and stable during storage, transport and shipment than classic serum samples.

Remote dried blood spot collection for inflammatory markers in older adults is feasible, reliable, and valid

Dried blood spots (DBS) provide a minimally invasive method to assess inflammatory markers and can be collected remotely at-home or in-person in the lab. However, there is a lack of methodological information comparing these different collection methods and in older adults. We investigated the feasibility (including adherence, yield, quality, and participant preferences) and measurement properties (reliability, validity) of remotely collected DBS inflammatory markers in older adults. Participants (N = 167, mean age = 72, range: 60-96 years) collected their own DBS (finger prick on filter paper) during three remote interviews over ∼ 6 months. Within 4-5 days on average of their last remote interview, a subset of 41 participants also attended an in-person lab visit that included a researcher-collected DBS sample, venous blood draw, and survey to assess participant preferences of DBS collection. DBS and venous blood were assayed for CRP, IL-6, and TNF-α. Adherence: 98% of expected DBS samples (493 out of 501) were completed and mailed back to the lab. Yield: 97% of DBS samples were sufficient for all assays. Quality: On average, 0.80 fewer optimal spots (60uL of blood that filled the entire circle) were obtained remotely vs. in-person (p = 0.013), but the number of useable or better spots (at least 30-40uL of blood) did not differ (p = 0.89). Preference: A slight majority of participants (54%) preferred in-person DBS collection. Reliability: DBS test-retest reliabilities were good: CRP (ICC = 0.74), IL-6 (ICC = 0.76), and TNF-α (ICC = 0.70). Validity: Inflammatory levels from DBS correlated strongly with levels from venous blood (r = 0.60-0.99) and correlated as expected with sociodemographic and physical health and function variables. Older adults can remotely collect their own DBS to acquire reliable and valid inflammatory data. Remote DBS collection is highly feasible and may allow for inflammatory markers to be assessed in larger, more representative samples than are possible with lab- or clinic-based research designs.

Self-Sampling by Adolescents at Home: Assessment of the Feasibility to Successfully Collect Blood Microsamples by Inexperienced Individuals

Blood microsampling has increasingly attracted interest in the past decades as a more patient-centric sampling approach, offering the possibility to collect a minimal volume of blood following a finger or arm prick at home. In addition to conventional dried blood spots (DBS), many different devices allowing self-sampling of blood have become available. Obviously, the success of home-sampling can only be assured when (inexperienced) users collect samples of good quality. Therefore, the feasibility of six different microsampling devices to collect capillary blood by inexperienced adolescents at home was evaluated. Participants (n = 95) were randomly assigned to collect blood (dried or liquid) at different time points using four of six different self-sampling devices (i.e., DBS, Mitra volumetric absorptive microsampling (VAMS), Capitainer B, Tasso M20, Minicollect tube and Tasso+ serum separator tube (SST)). The quality of the samples was visually inspected and analytically determined. Moreover, the participants' satisfaction was assessed via questionnaires. Although a majority succeeded based on the visual inspection, the success rate differed largely between the different devices. In general, the lowest success rate was obtained for the Minicollect tubes, although there is an opportunity and need for improvement for the other self-sampling devices as well. Hence, this also emphasizes the importance to assess the quality of samples collected by the target population prior to study initiation. In addition, visual classification by a trained individual was confirmed based on assessment of the analytical variability between replicates. Finally, self-sampling at home was overall (very) positively received by the participants.

Targeted and untargeted metabolomics and lipidomics in dried blood microsampling: Recent applications and perspectives

Blood microsampling (BµS) offers an alternative to conventional methods that use plasma or serum for profiling human health, being minimally invasive and cost effective, especially beneficial for vulnerable populations. We present a non-systematic review that offers a synopsis of the analytical methods, applications and perspectives related to dry blood microsampling in targeted and untargeted metabolomics and lipidomics research in the years 2022 and 2023. BµS shows potential in neonatal and paediatric studies, therapeutic drug monitoring, metabolite screening, biomarker research, sports supervision, clinical disorders studies and forensic toxicology. Notably, dried blood spots and volumetric absorptive microsampling options have been more extensively studied than other volumetric technologies. Therefore, we suggest that a further investigation and application of the volumetric technologies will contribute to the use of BµS as an alternative to conventional methods. Conversely, we support the idea that harmonisation of the analytical methods when using BµS would have a positive impact on its implementation.

Advancements in clinical approaches, analytical methods, and smart sampling for LC-MS-based protein determination from dried matrix spots

Determination of proteins from dried matrix spots using MS is an expanding research area. Mainly, the collected dried matrix sample is whole blood from a finger or heal prick, resulting in dried blood spots. However as other matrices such as plasma, serum, urine, and tear fluid also can be collected in this way, the term dried matrix spot is used as an overarching term. In this review, the focus is on advancements in the field made from 2017 up to 2023. In the first part reviews concerning the subject are discussed. After this, advancements made for clinical purposes are highlighted. Both targeted protein analyses, with and without the use of affinity extractions, as well as untargeted, global proteomic approaches are discussed. In the last part, both methodological advancements are being reviewed as well as the possibility to integrate sample preparation steps during the sample handling. The focus, of this so-called smart sampling, is on the incorporation of cell separation, proteolysis, and antibody-based affinity capture.

Emerging technologies: analytical lab vs. clinical lab perspective. Common goals and gaps to be filled in the pursuit of green and sustainable solutions

Analytical chemistry is a broad area of science comprised of many sub-disciplines. Although each sub-discipline has its own dominant trends, one trend is common to all of them: greenness and sustainability. Efforts to develop more ecological and environmentally friendly methods have been ongoing for over a decade with initial attempts largely focusing on limiting the necessary volume of solvents required and eliminating the use of toxic solvents. Over time, the miniaturization of analytical devices gained popularity as a way of not only reducing chemical usage, but also enabling analyses using smaller sample volumes and more "remote" applications (e.g., on-site sampling and analysis). Of course, miniaturization poses numerous challenges for researchers, for instance, in relation to the method's sensitivity and reproducibility. Developments in the design of detection systems have largely helped to mitigate these issues, but they also often restrict the potential for on-site analysis. Therefore, attempts have been made to improve analysis throughout the entire analytical process, from sampling through sample preparation and instrumental analysis to data handling. Furthermore, clinical chemistry labs must adhere to certain regulations and use certified protocols and materials, which precludes the rapid implementation of solutions developed in research labs. What are the obstacles in translating such innovations to practical applications, and what inventions can make a difference in the future? The answers to these two questions define the trends in analytical chemistry in the field of medical analysis.

Advancing Global Health Surveillance of Mycotoxin Exposures using Minimally Invasive Sampling Techniques: A State-of-the-Science Review

Mycotoxins are a heterogeneous group of toxins produced by fungi that can grow in staple crops (e.g., maize, cereals), resulting in health risks due to widespread exposure from human consumption and inhalation. Dried blood spot (DBS), dried serum spot (DSS), and volumetric tip microsampling (VTS) assays were developed and validated for several important mycotoxins. This review summarizes studies that have developed these assays to monitor mycotoxin exposures in human biological samples and highlights future directions to facilitate minimally invasive sampling techniques as global public health tools. A systematic search of PubMed (MEDLINE), Embase (Elsevier), and CINAHL (EBSCO) was conducted. Key assay performance metrics were extracted to provide a critical review of the available methods. This search identified 11 published reports related to measuring mycotoxins (ochratoxins, aflatoxins, and fumonisins) using DBS/DSS and VTS assays. Multimycotoxin assays adapted for DBS/DSS and VTS have undergone sufficient laboratory validation for applications in large-scale population health and human biomonitoring studies. Future work should expand the number of mycotoxins that can be measured in multimycotoxin assays, continue to improve multimycotoxin assay sensitivities of several biomarkers with low detection rates, and validate multimycotoxin assays across diverse populations with varying exposure levels. Validated low-cost and ultrasensitive minimally invasive sampling methods should be deployed in human biomonitoring and public health surveillance studies to guide policy interventions to reduce inequities in global mycotoxin exposures.

Revolutionizing Blood Collection: Innovations, Applications, and the Potential of Microsampling Technologies for Monitoring Metabolites and Lipids

Blood serves as the primary global biological matrix for health surveillance, disease diagnosis, and response to drug treatment, holding significant promise for personalized medicine. The diverse array of lipids and metabolites in the blood provides a snapshot of both physiological and pathological processes, with many routinely monitored during conventional wellness checks. The conventional method involves intravenous blood collection, extracting a few milliliters via venipuncture, a technique limited to clinical settings due to its dependence on trained personnel. Microsampling methods have evolved to be less invasive (collecting ≤150 µL of capillary blood), user-friendly (enabling self-collection), and suitable for remote collection in longitudinal studies. Dried blood spot (DBS), a pioneering microsampling technique, dominates clinical and research domains. Recent advancements in device technology address critical limitations of classical DBS, specifically variations in hematocrit and volume. This review presents a comprehensive overview of state-of-the-art microsampling devices, emphasizing their applications and potential for monitoring metabolites and lipids in blood. The scope extends to diverse areas, encompassing population studies, nutritional investigations, drug discovery, sports medicine, and multi-omics research.

Genotyping in patients with congenital adrenal hyperplasia by sequencing of newborn bloodspot samples

OBJECTIVES

Genotype-phenotype correlation in congenital adrenal hyperplasia (CAH) caused by 21-hydroxylase deficiency ranges from 45 to 97 %. We performed massively parallel sequencing of CYP21A2 on stored newborn bloodspot samples to catalogue the genotypes present in our patients with CAH and enable genotype-phenotype comparison.

METHODS

Participants ≤15 years old with clinically diagnosed CAH were recruited from The Sydney Children's Hospitals Network. Phenotype was classified from clinical and biochemical details in the medical record as salt wasting (SW), simple virilising (SV), non-classic (NC) or an intermediate phenotype (SW/SV; SV/NC). Amplicon-based sequencing for CYP21A2 was performed on stored newborn bloodspot samples by the New South Wales Newborn Bloodspot Screening Laboratory on MiSeq™Dx (Illumina, California). Available genetic test results were also obtained from the medical records.

RESULTS

Samples from 67 participants (43 % female, age 0.3-15 years) were sequenced, including 9 sibships. SW phenotype was present in 33/67 participants (49 %), SV in 9 (13 %) and NC in 16 (24 %). Intermediate phenotypes included SW/SV in seven participants (10 %) and SV/NC in two (3 %). Variants were identified in 90/116 alleles (78 %). A complete genotype was available in 47/67 participants (70 %). The most common genotype was homozygous c.293-13A/C>G (I2G) in 7/47 participants (15 %). Genotype correlated with the most commonly reported phenotype in 36/44 cases (82 %). Correlation was higher in SW and NC phenotypes.

CONCLUSIONS

This study uses genetic testing of newborn bloodspots to identify and characterise the genotypes present in an ethnically diverse Australian population with CAH. It further strengthens our knowledge of genotype-phenotype correlations in CAH.

Volumetric Absorptive Microsampling in the Analysis of Endogenous Metabolites

Volumetric absorptive microsampling (VAMS) has arisen as a relevant tool in biological analysis, offering simplified sampling procedures and enhanced stability. Most of the attention VAMS has received in the past decade has been from pharmaceutical research, with most of the published work employing VAMS targeting drugs or other exogenous compounds, such as toxins and pollutants. However, biomarker analysis by employing blood microsampling has high promise. Herein, a comprehensive review on the applicability of VAMS devices for the analysis of endogenous metabolites/biomarkers was performed. The study presents a full overview of the analysis process, incorporating all the steps in sample treatment and validation parameters. Overall, VAMS devices have proven to be reliable tools for the analysis of endogenous analytes with biological importance, often offering improved analyte stability in comparison with blood under ambient conditions as well as a convenient and straightforward sample acquisition model.

Quantitation of phenylalanine and tyrosine from dried Blood/Plasma spots with impregnated stable isotope internal standards (SIIS) by FIA-SRM

BACKGROUND

Dried Blood Spot (DBS) analysis has been used for identification and quantification of diseases and disorders in large populations. Simply collecting blood or plasma samples on cotton paper, followed with an organic solvent extraction, many small molecules can be detected and quantified. In a typical procedure of DBS analysis in newborn screening, stable isotope internal standards (SIIS) are added to extraction solvent as a reference. However, this way of employing SIIS does not reflect extraction efficiency, or protein binding issues, nor does it reflect potential degradation that could occur. In addition, punched-out discs from larger DBS are known to have imprecision typically ≥ 15%.

METHODS

We developed and tested an approach, internal quantitative DBS (iqDBS), which delivers an exact volume of whole blood or plasma to a paper disc that is impregnated with a dried concentration of SIIS for quantitation. Amino acids were derivatized to make butyl esters and measured using Flow Injection Analysis with Selected Reaction Monitoring (FIA-SRM).

RESULTS

We demonstrated with phenylalanine and tyrosine improved sensitivity and accuracy by applying iqDBS.

CONCLUSIONS

We established a new method for quantitative analysis of small molecules from dried blood spots that incorporates stable isotope internal standard at the time of blood collection.