Evaluation of the Performance and Hematocrit Independence of the HemaPEN as a Volumetric Dried Blood Spot Collection Device

A Validated Assay to Quantify Osimertinib and Its Metabolites, AZ5104 and AZ7550, from Microsampled Dried Blood Spots and Plasma

BACKGROUND

Osimertinib is an oral small-molecule tyrosine kinase receptor inhibitor used to treat non-small cell lung cancer (NSCLC) with a sensitizing epidermal growth factor receptor mutation. Patients may experience drug toxicity and require dose deescalation. The study aimed to quantitate osimertinib and its 2 active metabolites, AZ5104 and AZ7550, in microsampled dried blood spots (DBS) collected from patients with NSCLC using a hemaPEN device and compare them with plasma drug levels.

METHODS

A 6-min ultrahigh-performance liquid chromatography-tandem mass spectrometry method was developed and validated using plasma and DBS. The accuracy, selectivity, matrix effect, recovery, and stability were assessed using bioanalytical validation criteria. The hematocrit effect was investigated in DBS. Drug levels were measured in 15 patients with NSCLC, and the Bland-Altman method was used to compare measurements between plasma and DBS.

RESULTS

The validated assay determined accurate and precise quantities, respectively, for osimertinib in both plasma (93.2%-99.3%; 0.2%-2.3%) and DBS (96.7%-99.6%; 0.5%-10.3%) over a concentration of 1-729 ng/mL. The osimertinib metabolites, AZ5104 and AZ7550, were similarly validated in accordance with bioanalytical guidelines. For 30%-60% patient hematocrit, no hematocrit bias was observed with DBS for all analytes. The Bland-Altman method showed high concordance between plasma and DBS analyte levels. Stability experiments revealed that osimertinib and its metabolites were poorly stable in plasma at room temperature, whereas all analytes were stable in DBS for 10 days at room temperature.

CONCLUSIONS

The measurement of osimertinib, AZ5104, and AZ7550 from hemaPEN microsampled DBS is a convenient and reliable approach for therapeutic drug monitoring that produces measurements consistent with plasma drug levels.

Therapeutic drug monitoring of osimertinib in EGFR mutant non-small cell lung cancer by dried blood spot and plasma collection: A pilot study

AIMS

Therapeutic drug monitoring (TDM) has led to significant improvements in individualized medical care, although its implementation in oncology has been limited to date. Tyrosine kinase inhibitors (TKIs) are a group of therapies for which TDM has been suggested. Osimertinib is one such therapy used in the treatment of epidermal growth factor receptor (EGFR) mutation-driven lung cancer. Herein, we describe a prospective pilot study involving 21 patients on osimertinib primarily as a preliminary evaluation of drug levels in a real-world setting.

METHODS

Concentrations of the drug and its primary metabolites were measured with a validated liquid chromatography-mass spectrometry (LC-MS) assay across serial timepoints. As part of this study, inter-individual variability by dose and ethnicity as well as intra-individual variability across timepoints are explored. Furthermore, we attempted to validate dried blood spot (DBS)-based quantitation as an accurate alternative to plasma quantitation.

RESULTS

Successful quantitation of osimertinib and primary metabolites was achieved for our subjects. Compound plasma levels were highly correlated to DBS levels. There was no significant difference in concentrations with ethnicity or dosing or intra-individual variability across timepoints.

CONCLUSIONS

As such, we demonstrate that TDM for osimertinib is practical for future trials. We also validated the use of DBS as an alternative to conventional quantitation for exploration of TDM for osimertinib in larger trials and for other targeted therapies.

Enhancing drug development and clinical studies with patient-centric sampling using microsampling techniques: Opportunities, challenges, and insights into liquid chromatography-mass spectrometry strategies

Microsampling has revolutionized pharmaceutical drug development and clinical research by reducing sample volume requirements, allowing sample collection at home or nontraditional sites, minimizing animal and patient burden, and enabling more flexible study designs. This perspective paper discusses the transformative impact of microsampling and patient-centric sampling (PCS) techniques, emphasizing their advantages in drug development and clinical trials. We highlight the integration of liquid chromatography-mass spectrometry (LC-MS) strategies for analyzing PCS samples, focusing on our research experience and a review of current literatures. The paper reviews commercially available PCS devices, their regulatory status, and their application in clinical trials, underscoring the benefits of PCS in expanding patient enrollment diversity and improving study designs. We also address the operational challenges of implementing PCS, including the need for bridging studies to ensure data comparability between traditional and microsampling methods, and the analytical challenges posed by PCS samples. The paper proposes future directions for PCS, including the development of global regulatory standards, technological advancements to enhance user experience, the increased concern of sustainability and patient data privacy, and the integration of PCS with other technologies for improved performance in drug development and clinical studies. By advancing microsampling and PCS techniques, we aim to foster patient-centric approaches in pharmaceutical sciences, ultimately enhancing patient care and treatment efficacy.

Evaluation of Patient-Centric Sample Collection Technologies for Pharmacokinetic Assessment of Large and Small Molecules

Low-volume sampling devices offer the promise of lower discomfort and greater convenience for patients, potentially reducing patient burden and enabling decentralized clinical trials. In this study, we determined whether low-volume sampling devices produce pharmacokinetic (PK) data comparable to conventional venipuncture for a diverse set of monoclonal antibodies (mAbs) and small molecules. We adopted an open-label, non-randomized, parallel-group, single-site study design, with four cohorts of 10 healthy subjects per arm. The study drugs, doses, and routes of administration included: crenezumab (15 mg/kg, intravenous infusion), etrolizumab (210 mg, subcutaneous), GDC-X (oral), and hydroxychloroquine (HCQ, 200 mg, oral). Samples were collected after administration of a single dose of each drug using conventional venipuncture and three low-volume capillary devices: TassoOne Plus for liquid blood, Tasso-M20 for dry blood, both applied to the arm, and Neoteryx Mitra® for dry blood obtained from fingertips. Serum/plasma concentrations from venipuncture and TassoOne Plus samples overlapped and PK parameters were comparable for all drugs, except HCQ. After applying a baseline hematocrit value, the dry blood concentrations and PK parameters for the two monoclonal antibodies were comparable to those obtained from venipuncture. For the two small molecules, two bridging strategies were evaluated for converting dry blood concentrations to equivalent plasma concentrations. A baseline hematocrit correction and/or linear regression-based correction was effective for GDC-X, but not for HCQ. Additionally, the study evaluated the bioanalytical data quality and comparability from the various collection methods, as well as patient preference for the devices.

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.

Biological Fluid Microsampling for Therapeutic Drug Monitoring: A Narrative Review

Therapeutic drug monitoring (TDM) is a specialized area of laboratory medicine which involves the measurement of drug concentrations in biological fluids with the aim of optimizing efficacy and reducing side effects, possibly modifying the drug dose to keep the plasma concentration within the therapeutic range. Plasma and/or whole blood, usually obtained by venipuncture, are the "gold standard" matrices for TDM. Microsampling, commonly used for newborn screening, could also be a convenient alternative to traditional sampling techniques for pharmacokinetics (PK) studies and TDM, helping to overcome practical problems and offering less invasive options to patients. Although technical limitations have hampered the use of microsampling in these fields, innovative techniques such as 3-D dried blood spheroids, volumetric absorptive microsampling (VAMS), dried plasma spots (DPS), and various microfluidic devices (MDS) can now offer reliable alternatives to traditional samples. The application of microsampling in routine clinical pharmacology is also hampered by the need for instrumentation capable of quantifying analytes in small volumes with sufficient sensitivity. The combination of microsampling with high-sensitivity analytical techniques, such as liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS), is particularly effective in ensuring high accuracy and sensitivity from very small sample volumes. This manuscript provides a critical review of the currently available microsampling devices for both whole blood and other biological fluids, such as plasma, urine, breast milk, and saliva. The purpose is to provide useful information in the scientific community to laboratory personnel, clinicians, and researchers interested in implementing the use of microsampling in their routine clinical practice.

Dried blood spot sampling for therapeutic drug monitoring: challenges and opportunities

INTRODUCTION

The use of dried blood spots (DBS) has gained interest in the field of therapeutic drug monitoring (TDM) due to its potential advantages, such as minimally invasive capillary blood collection, potential stabilization of drugs and metabolites at room or high temperatures, and lower biohazard, allowing for inexpensive storage and transportation. However, there are several drawbacks to the clinical use of DBS in TDM, mostly related to hematocrit (Hct) effects, differences between venous and capillary blood concentrations, among others, that must be evaluated during analytical and clinical method validation.

AREA COVERED

This review focuses on the most recent publications on the applications of DBS sampling for TDM (2016-2022), with a special focus on the challenges presented by this alternative sampling strategy, as well as the opportunities for clinical applications. Real-life studies presenting clinical applications were reviewed.

EXPERT OPINION

With the availability of method development and validation guidelines for DBS-based methods in TDM, higher levels of assay validation standardization have been achieved, expanding the clinical applications of DBS sampling in patient care. New sampling devices that overcome the limitations of classical DBS, such as the Hct effects, will further encourage the use of DBS in routine TDM.

New perspectives for the therapeutic drug monitoring of tacrolimus: Quantification in volumetric DBS based on an automated extraction and LC-MS/MS analysis

Volumetric microsampling devices have been developed for home-based capillary blood sampling and are now increasingly proposed for the therapeutic drug monitoring (TDM) of immunosuppressive drugs. Our objective was to validate a LC-MS/MS method for tacrolimus quantification based on both a manual and an automated extraction of dried blood spots (DBS) collected with a volumetric microsampling device. DBS collection was performed by placing a drop of whole blood (WB) pre-spiked with tacrolimus onto a sealing film and placing the hemaPEN® device (Trajan Scientific and Medical, Melbourne, Australia) into the drop according to the device specifications. Tacrolimus was quantified using a fully automatic preparation module connected to a LCMS system (CLAM-3020® and LCMS-8060®, Shimadzu, Marne-la-Vallée, France). The method was validated analytically and clinically in accordance with the EMA and IATDMCT guidelines. The method was linear from 1 to 100 µg/L. Within- and between-run accuracy and precision fulfilled the validation criteria (biases and imprecision <15% or 20% for the lower limit of quantification). No hematocrit effect, matrix effect or carry-over was observed. No selectivity issue was identified and dilution integrity was confirmed. Tacrolimus in DBS was stable for 14 days at room temperature and +4°C, and for 72h at +60°C. There was a good correlation between tacrolimus concentrations measured in WB and in DBS of 20 kidney and liver transplant recipients (r=0.93 and 0.87, for manual and automated extraction respectively). A method for tacrolimus measurement in DBS collected with volumetric micro-sampling device, based on a fully automated process from pre-treatment to LC-MS/MS analysis was developed and validated according to analytical and clinical criteria. This performing sampling and analytical procedure opens the perspective of an easier, faster and more efficient TDM of tacrolimus for patients, clinicians and laboratories.

Evaluation of dried-blood spots and a hematocrit-independent procedure in lysosomal diseases screening using multiplexed tandem mass spectrometry assays

BACKGROUND

Dried blood spots (DBS) are widely used as a non-invasive sampling method, especially in newborn screening (NBS). Despite its numerous advantages, conventional DBS might be limited by the hematocrit effect when analyzing a punch, depending on its position in the blood spot. This effect could be avoided using hematocrit-independent sampling devices such as the hemaPEN®. This device collects blood through integrated microcapillaries, and a fixed blood volume is deposited on a pre-punched paper disc. NBS programs are increasingly poised to include lysosomal disorders, given the availability of treatments that improve clinical outcomes if detected early. In this study, the effect of hematocrit and punch position in the DBS on the assay of 6 lysosomal enzymes was evaluated on 3 mm discs pre-punched in hemaPEN® devices compared to 3 mm punches from the PerkinElmer 226 DBS.

METHODS

The enzyme activities were measured by multiplexed tandem mass spectrometry coupled to ultra-high performance liquid chromatography. Three hematocrit levels (23%, 35%, and 50%) and punching positions (center, intermediary, and border) were tested. Three replicates have been performed for each condition. A multivariate approach has been used along with a univariate method to assess the effect of the experimental design on each enzyme activity.

RESULTS

Hematocrit, punch position, and whole blood sampling method do not affect the assessment of enzyme activity using the NeoLSD® assay.

CONCLUSION

The results obtained from conventional DBS and the volumetric device HemaPEN® are comparable. These results underline the reliability of DBS for this test.

Microsampling tools for collecting, processing, and storing blood at the point-of-care

In the wake of the COVID-19 global pandemic, self-administered microsampling tools have reemerged as an effective means to maintain routine healthcare assessments without inundating hospitals or clinics. Finger-stick collection of blood is easily performed at home, in the workplace, or at the point-of-care, obviating the need for a trained phlebotomist. While the initial collection of blood is facile, the diagnostic or clinical utility of the sample is dependent on how the sample is processed and stored prior to transport to an analytical laboratory. The past decade has seen incredible innovation for the development of new materials and technologies to collect low-volume samples of blood with excellent precision that operate independently of the hematocrit effect. The final application of that blood (i.e., the test to be performed) ultimately dictates the collection and storage approach as certain materials or chemical reagents can render a sample diagnostically useless. Consequently, there is not a single microsampling tool that is capable of addressing every clinical need at this time. In this review, we highlight technologies designed for patient-centric microsampling blood at the point-of-care and discuss their utility for quantitative sampling as a function of collection material and technique. In addition to surveying methods for collecting and storing whole blood, we emphasize the need for direct separation of the cellular and liquid components of blood to produce cell-free plasma to expand clinical utility. Integrating advanced functionality while maintaining simple user operation presents a viable means of revolutionizing self-administered microsampling, establishing new avenues for innovation in materials science, and expanding access to healthcare.

A targeted UHPLC-MS/MS method to monitor lipidomic changes during a physical effort: optimization and application to blood microsamples from athletes

In recent years, lipidomics have been widely developed to try to better understand many diseases or physical conditions. In this study, the aim was to evaluate the possibility to conduct reliable lipidomic studies using hemaPEN® microsampling devices. Targeted lipidomic analysis was applied to investigate the impact of a short and intense physical activity on lipids blood concentration. HemaPEN® microsampling device was used to easily collect several samples directly on an athletics track. This device allows the accurate collection of four blood samples (2.74 µL each) in a non-invasive way and without any specific skills. In this study, nineteen healthy volunteers aged from 19 to 27 were included. Participants ran 400 m warm-up and 1600 m as fast as possible. Blood samples were collected at five different time points. One sample was collected before the exercise, two during the physical activity and two after. An extraction process as well as an ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) method were optimized to follow-up 11 compounds in these small volumes of blood. Blood concentration of five out of the eleven targeted analytes were significantly influenced by the physical exercise. Blood concentration of arachidonic acid, sphingosine and lactic acid were significantly increased after exercise, while concentration of 14:0 lysophosphatidylcholine and 18:1 lysophosphatidylcholine were significantly decreased.

The development of microfluidic-based western blotting: Technical advances and future perspectives

Over the past two decades significant technical advancement in the field of western blotting has been made possible through the utilization of microfluidic technologies. In this review we provide a critical overview of these advancements, highlighting the advantages and disadvantages of each approach. Particular attention is paid to the development of now commercially available systems, including those for single cell analysis. This review also discusses more recent developments, including algorithms for automation and/or improved quantitation, the utilization of different materials/chemistries, use of projection electrophoresis, and the development of triBlots. Finally, the review includes commentary on future advances in the field based on current developments, and the potential of these systems for use as point-of-care devices in healthcare.

Liquid chromatography-tandem mass spectrometry for therapeutic drug monitoring of immunosuppressants and creatinine from a single dried blood spot using the Capitainer® qDBS device

In recent years, a lot of attention has been given to a more patient-centric therapeutic drug monitoring (TDM) of immunosuppressant drugs (tacrolimus, sirolimus, everolimus and cyclosporin A) by the use of microsampling techniques. By adopting Dried Blood Spots (DBS) after a finger prick, instead of conventional venous blood draws, follow-up can (partially) be established from patients' homes. Despite the many advantages of DBS, one of the major disadvantages associated with this technique is the well described hematocrit (hct) effect. In order to overcome the hct area bias, different strategies have been proposed, amongst which the use of dried blood sampling techniques based on the volumetric collection of blood. The aim of this study was to evaluate the use of the Capitainer® qDBS (quantitative Dried Blood Spot) device for the combined TDM of four immunosuppressants and creatinine from a single qDBS. The set-up of an adequate sample preparation allowing both immunosuppressants and creatinine quantification was one of the key challenges in the method development due to device-specific interferences. Liquid chromatography tandem-mass spectrometry methods for the quantification of tacrolimus, sirolimus, everolimus, cyclosporin A and creatinine from qDBS (10 μL) were developed and validated based on international guidelines, also taking into account DBS-specific parameters. The methods proved to be accurate and reproducible, with absolute biases below 10% and within-run CVs (%) below 8% over a calibration range from 1 to 50 ng/mL for tacrolimus, sirolimus and everolimus, 20-1500 ng/mL for cyclosporin A, and 15-700 μmol/L for creatinine. Reproducible (CV < 15%) IS-compensated relative recovery values were obtained, showing no hematocrit-dependence (compared to a hct of 0.37), except for cyclosporin A at higher hct values. Application on venous blood left-over patient samples showed good agreement between the results of Capitainer® qDBS and whole blood with 98% (47/48), 93% (41/44), 89% (41/46), 88% (38/43) and 89% (116/131) of the samples lying within 20% of the whole blood result for tacrolimus, sirolimus, everolimus, cyclosporin A and plasma/serum for creatinine, respectively. For creatinine a blood/plasma ratio of 0.85 was found and used to convert qDBS results to plasma/serum results. As a next step, capillary finger prick samples will need to demonstrate the clinical applicability of the method in a real life setting.

Dried blood microsampling-assisted therapeutic drug monitoring of immunosuppressants: An overview

In the field of solid organ transplantation, chemotherapy and autoimmune disorders, treatment with immunosuppressant drugs requires intensive follow-up of the blood concentrations via therapeutic drug monitoring (TDM) because of their narrow therapeutic window and high intra- and inter-subject variability. This requires frequent hospital visits and venepunctures to allow the determination of these analytes, putting a high burden on the patients. In the context of patient-centric thinking, it is becoming increasingly established that at least part of these conventional blood draws could be replaced by microsampling, allowing home-sampling and increasing the quality of life for these patients. In this review we discuss the published methods - mostly using liquid chromatography coupled to tandem mass spectrometry - that have utilized (volumetric) dried blood samples as an alternative for conventional liquid whole blood for the TDM of immunosuppressant drugs. Furthermore, some pre-analytical considerations using DBS or volumetric alternatives are considered, as well as the applicability on clinical samples. The implementation status in clinical practice is also discussed, including (1) the cost-effectiveness of this approach compared to venepuncture, (2) the availability of multiplexed methods, (3) the status of harmonization and (4) patient perception. A brief perspective on potential future developments for the dried blood-based TDM of immunosuppressant drugs is provided, by considering how obstacles for the implementation of these strategies into clinical practice might be overcome.

Proteome Analysis of Whole Blood Collected by Volumetric Absorptive Microsampling

Proteomic biomarker discovery and analysis from human biofluids using liquid chromatography-mass spectrometry (LC-MS) is an area of intense biomedical research. There is a growing interest to analyze microsampled patient blood specimens as this is potentially more patient-friendly enabling at-home and bedside self-collection of small blood volumes. However, there are limited studies applying LC-MS proteomic analysis of whole blood as it is dominated by red blood cell proteins such as hemoglobin which suppresses the detection of other less abundant proteins. Volumetric absorptive microsampling (VAMS) devices overcome this issue in part by providing a trapping matrix which allows depletion of abundant blood cell proteins through washing, prior to proteolysis and LC-MS. This approach allows the analysis of proteins from erythrocytes, leukocytes, and plasma and leads to deeper proteomic coverage compared to conventional plasma proteomics, increasing the prospects to discover novel biomarker proteins.

Leveraging patient-centric sampling for clinical drug development and decentralized clinical trials: Promise to reality

Advances in the technologies to enable patient-centric sampling (PCS) have the potential to improve blood sample collection by enabling clinical trial participants to collect samples via self-collection or with the help of a caregiver in their home. Typically, blood samples to assess pharmacokinetics and pharmacodynamics of a drug during clinical development are collected at a clinical site via venous blood draw. In this position paper by the International Consortium for Innovation and Quality in Pharmaceutical Development (IQ), the potential value PCS can bring to patients, to the clinical datasets generated, and to clinical trial sponsors is discussed, along with considerations for program decision making, bioanalytical feasibility, operations, and regulatory implications. With an understanding of the value of PCS and considerations when implementing during clinical drug development, we can bring the promise of PCS closer to reality and enable decentralized clinical trials.

Evaluation of hemaPEN® sampling device for measurement of cocaine and metabolites in capillary blood by LC-MS/MS

Background: Dried blood spot sampling has been reported for on-site collection of specimens, but measurements are affected by blood hematocrit, and special handling is required, especially for forensic applications. The hemaPEN^® blood collection device was developed to produce spots with constant volume. Results: Linearity between 1 and 500 ng/ml was shown for cocaine and the metabolites benzoylecgonine and cocaethylene. The assay demonstrated acceptable precision and accuracy, and analytes were stable for 7 days when kept inside hemaPEN devices. Accuracy of the assay was affected by hematocrit but was within acceptable limits. Conclusion: Use of the hemaPEN, which retains dried blood within the device, could be advantageous for the quantification of illicit drugs in capillary blood compared with conventional dried blood spot collection.

Advanced Microsamples: Current Applications and Considerations for Mass Spectrometry-Based Metabolic Phenotyping Pipelines

Microsamples are collections usually less than 50 µL, although all devices that we have captured as part of this review do not fit within this definition (as some can perform collections of up to 600 µL); however, they are considered microsamples that can be self-administered. These microsamples have been introduced in pre-clinical, clinical, and research settings to overcome obstacles in sampling via traditional venepuncture. However, venepuncture remains the sampling gold standard for the metabolic phenotyping of blood. This presents several challenges in metabolic phenotyping workflows: accessibility for individuals in rural and remote areas (due to the need for trained personnel), the unamenable nature to frequent sampling protocols in longitudinal research (for its invasive nature), and sample collection difficulty in the young and elderly. Furthermore, venous sample stability may be compromised when the temperate conditions necessary for cold-chain transport are beyond control. Alternatively, research utilising microsamples extends phenotyping possibilities to inborn errors of metabolism, therapeutic drug monitoring, nutrition, as well as sport and anti-doping. Although the application of microsamples in metabolic phenotyping exists, it is still in its infancy, with whole blood being overwhelmingly the primary biofluid collected through the collection method of dried blood spots. Research into the metabolic phenotyping of microsamples is limited; however, with advances in commercially available microsampling devices, common barriers such as volumetric inaccuracies and the ‘haematocrit effect’ in dried blood spot microsampling can be overcome. In this review, we provide an overview of the common uses and workflows for microsampling in metabolic phenotyping research. We discuss the advancements in technologies, highlighting key considerations and remaining knowledge gaps for the employment of microsamples in metabolic phenotyping research. This review supports the translation of research from the ‘bench to the community’.

Development of Certified Reference Material for Amino Acids in Dried Blood Spots and Accuracy Assessment of Disc Sampling

To achieve the measurement reliability of amino acids used as diagnostic markers in clinical fields, establishing a reference measurement system is required, in which certified reference materials (CRMs) are an essential step in the hierarchy of measurement traceability. This study describes the development of dried blood spot (DBS) CRMs for amino acid analysis with complete measurement traceability to the International System of Units (SI). Six essential amino acids—proline, valine, isoleucine, leucine, phenylalanine, and tyrosine—were analyzed using isotope-dilution liquid chromatography–mass spectrometry (ID-MS). For minimizing measurement bias and uncertainty overestimation, whole spots with 50 μL of whole blood were adopted in the certification. The between-spot homogeneities by whole spot sampling were lower than 2.1%. The relative expanded uncertainties of the six amino acids in the developed DBS CRMs were lower than 5.7% at 95% confidence. The certified values are traceable to SI through both gravimetric preparation and the primary method in certification, ID-MS. Comparison among DBS testing laboratories revealed discrepancies between the whole spot and disc sampling methods. The actual sampling volume was accurately estimated by weighing, which revealed the possibility of underestimation in routine DBS testing. The candidate CRMs can support the standardization of DBS testing for amino acids through the qualification and validation of many kinds of measurement procedures to compensate the measurement bias caused by matrix-specific sampling error.

Multi-omics analysis from archival neonatal dried blood spots: limitations and opportunities

Newborn screening (NBS) programs operate in many countries, processing millions of dried bloodspot (DBS) samples annually. In addition to early identification of various adverse health outcomes, these samples have considerable potential as a resource for population-based research that could address key questions related to child health. The feasibility of archival DBS samples for emerging targeted and untargeted multi-omics analysis has not been previously explored in the literature. This review aims to critically evaluate the latest advances to identify opportunities and challenges of applying omics analyses to NBS cards in a research setting. Medline, Embase and PubMed databases were searched to identify studies utilizing DBS for genomic, proteomic and metabolomic assays. A total of 800 records were identified after removing duplicates, of which 23 records were included in this review. These papers consisted of one combined genomic/metabolomic, four genomic, three epigenomic, four proteomic and 11 metabolomic studies. Together they demonstrate that the increasing sensitivity of multi-omic analytical techniques makes the broad use of NBS samples achievable for large cohort studies. Maintaining the pre-analytical integrity of the DBS sample through storage at temperatures below -20 °C will enable this important resource to be fully realized in a research capacity.

Solutions for hematocrit bias in dried blood spot hormone analysis

Over the last years, dried blood spot (DBS) sampling has gained significant interest due to development of analytical techniques combined with DBS, the simplicity and low cost of the method. Despite its wide use, DBS sampling can lead to inaccurate results due to the impact of the hematocrit (Hct) on the analysis. Some analytes have shown to be hardly impacted by Hct values. However, in other cases, a significant impact of Hct is observed, which requires the use of alternative approaches to circumvent this issue. This review describes the possible impact of Hct-related bias in DBS sampling in the context of hormone analysis and discusses the different methodologies that can be used to overcome this bias to ensure accurate results.

Microsampling: A role to play in Covid-19 diagnosis, surveillance, treatment and clinical trials

The outbreak of the new coronavirus disease changed the world upside down. Every day, millions of people were subjected to diagnostic testing for Covid-19, all over the world. Molecular tests helped in the diagnosis of current infection by detecting the presence of viral genome whereas serological tests helped in detecting the presence of antibody in blood as well as contributed to vaccine development. This testing helped in understanding the immunogenicity, community prevalence, geographical spread and conditions post-infection. However, with the contagious nature of the virus, biological specimen sampling involved the risk of transmission and spread of infection. Clinic or pathology visit was the most concerning part. Trained personnel and resources was another barrier. In this scenario, microsampling played an important role due to its most important advantage of remote, contactless, small volume and self-sampling. Minimum requirements for sample storage and ease of shipment added value in this situation. The highly sensitive instruments and validated assay formats assured the accuracy of results and stability of samples. Microsampling techniques are contributing effectively to the Covid-19 pandemic by reducing the demand for clinical staff in population-level testing. The validated and established applications supported the use of microsampling in diagnosis, therapeutic drug monitoring, development of treatment or vaccines and clinical trials for Covid-19.

Hematocrit and standardization in DBS analysis: A practical approach for hormones mainly present in the plasma fraction

BACKGROUND AND AIM

Dried blood spot (DBS) sampling has many advantages over conventionally used blood samples, but is thought to suffer from hematocrit related issues. The aim of our research was to investigate whether reliable results can be obtained without bothering about hematocrit effects in DBS analysis of analytes that are mainly present in the plasma compartment.

MATERIALS AND METHODS

Venous blood samples with variation in hematocrit and spotted volume were prepared. Spot diameter and 25-OH Vitamin D₃ and testosterone concentrations were measured. Moreover, DBS and plasma concentrations of 25-OH Vitamin D₃, testosterone and hematocrit were determined in random patient samples.

RESULTS

DBS spot size was linearly related to hematocrit. Measured DBS concentrations of 25-OH Vitamin D₃ and testosterone were independent of hematocrit and spotted volume. Determining the relation between plasma and DBS concentration resulted in a factor that can be used to convert DBS concentrations to standardized plasma concentrations.

CONCLUSION

Addressing the hematocrit issue is not necessary for hormones that are mainly present in the plasma compartment. The relation between plasma and DBS concentration can be used to convert DBS concentrations to standardized plasma concentrations which makes interpretation of DBS concentrations easier.

Microsampling Devices for Routine Therapeutic Drug Monitoring-Are We There Yet?

BACKGROUND

The use of microsampling for therapeutic drug monitoring (TDM) is increasingly feasible as sensitive methods have become more accessible. There exists an increasing interest in the use of microsampling, and new microsampling devices and techniques can potentially improve patient convenience and care, among other features. This review provides an update on currently validated methods for measuring drugs pertinent to TDM, including data from clinical samples.

METHODS

A literature record search was undertaken, including PubMed and Google Scholar. Reports that included the use of microsampling to measure concentrations of drugs associated with TDM were reviewed and included if data from patient samples were reported. The studies are described in brief, including sample preparation and analyte stability, with the most pertinent findings reported.

RESULTS

Sensitive analyses and innovative designs and materials have resulted in an increasing number of reported evaluations and validations for measuring drugs using microsamples. Novel designs largely overcome common problems associated with traditional dried blood spot sampling. Although examples of patient self-sampling are rare at present, studies that evaluated feedback found it to be largely positive, revealing the feasibility of microsampling for TDM.

CONCLUSIONS

Microsampling is suited to the TDM of numerous drugs in diverse situations, and it will play an increasingly important role. The issues with traditional dried blood spot samples have been largely overcome by employing novel methods to obtain volumetric samples.

Alternative Sampling Devices to Collect Dried Blood Microsamples: State-of-the-Art

ABSTRACT

Dried blood spots (DBS) have been used in newborn screening programs for several years. More recently, there has been growing interest in using DBS as a home sampling tool for the quantitative determination of analytes. However, this presents challenges, mainly because of the well-known hematocrit effect and other DBS-specific parameters, including spotted volume and punch site, which could add to the method uncertainty. Therefore, new microsampling devices that quantitatively collect capillary dried blood are continuously being developed. In this review, we provided an overview of devices that are commercially available or under development that allow the quantitative (volumetric) collection of dried blood (-based) microsamples and are meant to be used for home or remote sampling. Considering the field of therapeutic drug monitoring (TDM), we examined different aspects that are important for a device to be implemented in clinical practice, including ease of patient use, technical performance, and ease of integration in the workflow of a clinical laboratory. Costs related to microsampling devices are briefly discussed, because this additionally plays an important role in the decision-making process. Although the added value of home sampling for TDM and the willingness of patients to perform home sampling have been demonstrated in some studies, real clinical implementation is progressing at a slower pace. More extensive evaluation of these newly developed devices, not only analytically but also clinically, is needed to demonstrate their real-life applicability, which is a prerequisite for their use in the field of TDM.

Blood Microsampling to Monitor Metabolic Profiles During Physical Exercise

Monitoring approaches and technical improvements are key factors to improve a sportsman’s health, training, and recovery after an injury. In this study, a targeted metabolomics approach using microsampling with hemaPEN^® was developed to measure changes in blood concentrations of nine amino acids and four organic acids before, during, and after exercise. The aim of this research project was to investigate if a reliable monitoring of metabolite levels during sports activity can be achieved by collecting one drop of whole blood at different time points. A hemaPEN device is an easy-to-use and noninvasive microsampling technique designed to collect four accurate and precise blood volumes simultaneously (10.96 µl). Twenty healthy volunteers between 19 and 30 years of age were included in this study. Physical activity consisted in running as fast as possible 1,600 m after 400 m warm-up. One drop of blood was collected at five time points: before exercise, after 800-m running, after 1,600 m, and 30 min and 60 min after finishing the exercise. The influence of physical activity on metabolite levels was evaluated using two ultrahigh-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) methods. Analytical performance criteria such as metabolite stability, method precision, trueness, and accuracy were found to be satisfactory. Expected significant metabolic changes were identified for lactic acid, main TCA cycle intermediates, and some amino acids (e.g., creatinine, choline, and taurine). This preliminary study performed on a small cohort demonstrated a high interest of using microsampling for fluxomics analysis, not only to collect quickly and easily biological samples during sports events but also because it is much easier to store and to process the samples than classical plasma/serum samples obtained by venipuncture. The present results open new avenue for fluxomics analysis in the context of health care.

Assessment of capillary volumetric blood microsampling for the analysis of central nervous system drugs and metabolites

Therapeutic drug monitoring (TDM) is an important tool for correlating the administered drug dose to drug and metabolite concentrations in the body and to therapeutic and adverse effects. In the case of treatment with drugs active on the central nervous system (CNS), frequent TDM becomes really useful, especially for patient compliance checking and for therapy optimisation. The selective serotonin reuptake inhibitors (SSRIs) fluoxetine and sertraline, chosen as target compounds for this study, are two antidepressants mainly used for major depression, but also for obsessive-compulsive disorder associated with neurodegenerative diseases and for eating disorders. Microsampling approaches can be used to make TDM patient-friendly, by means of minimally invasive fingerpricking instead of classic invasive venipuncture. In this study, an innovative volumetric microsampling approach based on the use of hemaPEN technology is proposed to simultaneously obtain four identical dried whole blood microsamples by means of a single capillary sampling. The developed strategy shows significant advantages in terms of blood collection and storage, fast and feasible extraction procedure and sensitive LC-MS/MS analysis, also providing satisfactory validation results (extraction yield >81%, RSD <12.0%, and <6.3% loss in analyte stability after 3 months). The proposed methodology has proven to be sound and reliable for application to the TDM of psychiatric patients treated with antidepressant drugs such as fluoxetine and sertraline. The original capillary volumetric microsampling procedure using hemaPEN has been demonstrated to be suitable for the accurate sampling of capillary whole blood, in order to be successfully exploited in self- and home-sampling procedures in future and to pave the way for precision medicine approaches for the treatment of CNS disorders.

The Evolving Role of Microsampling in Therapeutic Drug Monitoring of Monoclonal Antibodies in Inflammatory Diseases

Monoclonal antibodies (mAbs) have been extensively developed over the past few years, for the treatment of various inflammatory diseases. They are large molecules characterized by complex pharmacokinetic and pharmacodynamic properties. Therapeutic drug monitoring (TDM) is routinely implemented in the therapy with mAbs, to monitor patients’ treatment response and to further guide dose adjustments. Serum has been the matrix of choice in the TDM of mAbs and its sampling requires the visit of the patients to laboratories that are not always easily accessible. Therefore, dried blood spots (DBS) and various microsampling techniques have been suggested as an alternative. DBS is a sampling technique in which capillary blood is deposited on a special filter paper. It is a relatively simple procedure, and the patients can perform the home-sampling. The convenience it offers has enabled its use in the quantification of small-molecule drugs, whilst in the recent years, studies aimed to develop microsampling methods that will facilitate the TDM of mAbs. Nevertheless, hematocrit still remains an obstacle that hinders a more widespread implementation of DBS in clinical practice. The introduction of novel analytical techniques and contemporary microsampling devices can be considered the steppingstone to the attempts made addressing this issue.

A validated surrogate analyte LC-MS/MS assay for quantification of endogenous cortisol in human whole blood

Cortisol is a steroid hormone that is frequently measured as a marker of stress, inflammation, and immune function. While commonly analyzed in saliva, hair, blood plasma and urine, a recent trend towards whole blood-based at-home collection devices has emerged, which necessitates development of more sensitive assays for cortisol in whole blood. To support the implementation of a patient-centric sampling approach in a drug development program, a fit-for-purpose surrogate analyte-based liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay for cortisol in whole blood was developed using ¹³C₃-cortisol as a surrogate analyte and cortisol-d6 as the internal standard. The surrogate analyte approach was chosen due to a lack of available cortisol-free whole blood and the absence of appropriately representative surrogate matrices. Samples were prepared using supported liquid extraction, and the LC-MS/MS analysis consisted of a 4.00 min analytical run. The method demonstrated linearity between 0.500 and 500 ng/mL of ¹³C₃-cortisol, and accuracy, precision and robustness were all acceptable per current regulatory guidance for bioanalytical method validation of chromatographic assays for cortisol- and ¹³C₃-cortisol-based quality control (QC) samples when quantified against a ¹³C₃-cortisol calibration curve. The acceptable robustness of cortisol-based QCs when quantified against a ¹³C₃-cortisol-based calibration curve also suggests parallelism between the analytes. These results indicate a viable surrogate analyte method, that is fit-for-purpose to analyze whole blood cortisol levels using a surrogate analyte LC-MS/MS approach. Evaluation of patient samples showed very promising comparability between whole blood and plasma cortisol concentrations, suggesting that whole blood could be used in place of or in addition to a plasma-based sampling protocol in clinical trials analyzing cortisol. Overall, this method presents a novel tool that is a first step in supporting the trend towards sample miniaturization and at-home sample collection, and may be readily used in clinical and diagnostic settings.

Assessment of a dried blood spot C-reactive protein method to identify disease flares in rheumatoid arthritis patients

Rheumatoid arthritis (RA) is characterised by painful, stiff and swollen joints. RA features sporadic 'flares' or inflammatory episodes-mostly occurring outside clinics-where symptoms worsen and plasma C-reactive protein (CRP) becomes elevated. Poor control of inflammation results in higher rates of irreversible joint damage, increased disability, and poorer quality of life. Flares need to be accurately identified and managed. A method comparison study was designed to assess agreement between CRP values obtained by dried blood spot (DBS) versus conventional venepuncture sampling. The ability of a weekly DBS sampling and CRP test regime to detect flare outside the clinic was also assessed. Matched venepuncture and finger lancet DBS samples were collected from n = 100 RA patients with active disease at baseline and 6 weeks (NCT02809547). A subset of n = 30 RA patients submitted weekly DBS samples over the study period. Patient demographics, including self-reported flares were recorded. DBS sample CRP measurements were made by enzyme-linked immunosorbent assay, and venepuncture samples by a reference immunoturbometric assay. Data was compared between sample types by Bland-Altman and weighted Deming regression analyses. Flare detection sensitivity and specificity were compared between 'minimal' baseline and 6 week sample CRP data and the 'continuous' weekly CRP data. Baseline DBS ELISA assay CRP measures yielded a mean positive bias of 2.693 ± 8.640 (95% limits of agreement - 14.24 to 19.63%), when compared to reference assay data. Deming regression revealed good agreement between the DBS ELISA method and reference assay data, with baseline data slope of 0.978 and intercept -0.153. The specificity of 'continuous' area under the curve (AUC) CRP data (72.7%) to identify flares, was greater than 'minimal' AUC CRP data (54.5%). This study indicates reasonable agreement between DBS and the reference method, especially at low to mid-range CRP values. Importantly, longitudinal CRP measurement in RA patients helps to clearly identify flare and thus could assist in remote monitoring strategies and may facilitate timely therapeutic intervention.Trial registration: The Remote Arthritis Disease Activity MonitoR (RADAR) study was registered on 22/06/2016 at ClinicalTrials.gov Identifier: NCT02809547. https://clinicaltrials.gov/ct2/show/NCT02809547 .

In vitro testing of the hemaPEN microsampling device for the quantification of acetaminophen in human blood

Background: The hemaPEN is a liquid microsampling device for the reproducible collection and storage of blood samples as dried blood spots, for subsequent quantitative analysis. Materials & methods: We examined the device’s ability to collect accurate and precise blood volumes, at different hematocrit levels, via in vitro studies using acetaminophen in human blood. We also investigated the impact of different user training approaches on device performance. Results: The hemaPEN demonstrated acceptable volumetric accuracy and precision, regardless of the training medium used. Issues with apparent hematocrit-dependent bias were found to be associated with the extraction process, rather than the volumetric performance of the device. Conclusion: The hemaPEN is capable of readily producing high quality blood microsamples for reproducible and accurate quantitative bioanalysis.

Technological advancement in dry blood matrix microsampling and its clinical relevance in quantitative drug analysis

In the past few decades, dried blood matrix biosampling has witnessed a marvelous interest among the researcher due to its user-friendly operation during blood sampling in preclinical and clinical applications. It also complies with the basic 3Rs (reduce, reuse and recycle) philosophy. Because of comparative simplicity, a huge number of researchers are paying attention to its technological advancements for widespread application in the bioanalysis and diagnosis arena. In this review, we have explained different approaches to be considered during dried blood matrix based microsampling including their clinical relevance in therapeutic drug monitoring. We have also discussed various strategies for avoiding and minimizing major unwanted analytical interferences associated with this technique during drug quantification. Further, various recent technological advancement in microsampling devices has been discussed correlating their clinical applications.

Barriers and opportunities for the clinical implementation of therapeutic drug monitoring in oncology

There are few fields of medicine in which the individualisation of medicines is more important than in the area of oncology. Under-dosing can have significant ramifications due to the potential for therapeutic failure and cancer progression; by contrast, over-dosing may lead to severe treatment-limiting side effects, such as agranulocytosis and neutropenia. Both circumstances lead to poor patient prognosis and contribute to the high mortality rates still seen in oncology. The concept of dose individualisation tailors dosing for each individual patient to ensure optimal drug exposure and best clinical outcomes. While the value of this strategy is well recognised, it has seen little translation to clinical application. However, it is important to recognise that the clinical setting of oncology is unlike that for which therapeutic drug monitoring (TDM) is currently the cornerstone of therapy (e.g. antimicrobials). Whilst there is much to learn from these established TDM settings, the challenges presented in the treatment of cancer must be considered to ensure the implementation of TDM in clinical practice. Recent advancements in a range of scientific disciplines have the capacity to address the current system limitations and significantly enhance the use of anticancer medicines to improve patient health. This review examines opportunities presented by these innovative scientific methodologies, specifically sampling strategies, bioanalytics and dosing decision support, to enable optimal practice and facilitate the clinical implementation of TDM in oncology.

Fluispotter, a novel automated and wearable device for accurate volume serial dried blood spot sampling

Aim: A novel automated serial dried blood spot (DBS) sampler, 'Fluispotter', was tested for its sampling performance. Materials & methods: An LC-MS/MS method was developed for the analysis of cortisol in DBS samples serially spotted by Fluispotter. The cortisol concentrations in 148 paired DBS and plasma samples were compared across a hematocrit (HCT) range of 22-55%. Results: The interassay accuracy and precision were <10%. Overall assay bias was negligible across the HCTs tested when analyzing the whole-spot DBS samples. The accuracy and precision of the blood volume in 10 μl DBS samples spotted by Fluispotters and micropipettes were within 3%. Deming regression and Bland-Altman analysis showed a good agreement of DBS-predicted and measured plasma cortisol. Conclusion: The Fluispotter performed serial sampling with high accuracy and precision of the sample blood volume.