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

Microsampling Techniques Suitable for Therapeutic Drug Monitoring of Antipsychotics

BACKGROUND

Therapeutic drug monitoring (TDM) of antipsychotics for dose titration or detection of noncompliance is not uncommon in daily practice. Normally, TDM implies measuring a drug concentration in venous blood samples. This technique is invasive and requires trained assistants and patients normally need to go to an outpatient clinic. Over the past decades, sensitivity of analytical equipment has improved leading to a growing interest in microsampling techniques. These techniques are minimally invasive, require a small volume (<100 μL), usually result in stable samples, and can be collected by the patient or a caregiver at home. Before a microsampling technique can be used in daily routine, proper method development and a clinical validation study should be performed.

METHOD

For this review, the databases of PubMed and Embase were systematically searched. Currently available microsampling techniques for antipsychotics in blood, serum, or plasma are summarized. Subsequently, it has also been assessed whether these techniques are sufficiently validated for TDM monitoring in daily practice.

RESULTS

Several microsampling techniques are available today, for example, dried blood spot sampling, dried plasma extraction cards, and volumetric absorptive microsampling. Eighteen studies were identified in which a microsampling technique for 1 or a few antipsychotics was chemically analytically and clinically validated. However, the majority of these studies have relevant shortcomings that mean its usefulness for different antipsychotics is not yet well established.

CONCLUSIONS

Microsampling for TDM can be recommended for patients using clozapine. For TDM of other antipsychotics, it is a very promising development.

Volumetric absorptive microsampling for the therapeutic drug monitoring of psychiatric patients treated with cariprazine

Psychiatric disorders are usually treated with antipsychotic agents belonging to different pharmacological and chemical classes, the most recent ones collectively known as "third-generation antipsychotics", such as cariprazine, approved in 2015 for the treatment of patients affected by schizophrenia. For these patients, a frequent therapeutic drug monitoring (TDM) becomes essential to assess compliance and to optimise and personalise their therapy, also due to cariprazine interindividual variability and narrow therapeutic range. In this study, a bioanalytical method featuring miniaturised sampling and pretreatment was developed, based on volumetric absorptive microsampling (VAMS) for TDM of psychiatric patients under cariprazine treatment and compared to a reference method based on fluid plasma analysis. Minimally invasive whole blood VAMS was coupled to an original instrumental method based on ultra-high performance liquid chromatography hyphenated to mass spectrometry (UHPLC-MS). A feasible and streamlined, yet reliable VAMS pretreatment protocol was carefully optimised and the VAMS-UHPLC-MS methodology was validated with satisfactory results in terms of linearity (r2 > 0.9970 in the 1.5-100 ng/mL range), precision (%RSD < 11.7), extraction yield (> 90.0 %) and matrix effect (8.2 ≤ %RE ≤ 10.9). Finally, the microsampling approach coupled to UHPLC-MS was successfully applied to the TDM of psychiatric patients treated with cariprazine and compared with standard fluid plasma analysis, providing reliable quali-quantitative results, and proving to be readily applicable to the clinical practice in TDM programs as a useful alternative to cariprazine plasma analysis. This is the first report of a successful microsampling application, and in particular the first report of VAMS application, for the TDM of cariprazine.

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.

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.

VAMS-Based Blood Capillary Sampling for Mass Spectrometry-Based Human Metabolomics Studies

Volumetric absorptive microsampling (VAMS) is a recently developed sample collection method that enables single-drop blood collection in a minimally invasive manner. Blood biomolecules can then be extracted and processed for analysis using several analytical platforms. The integration of VAMS with conventional mass spectrometry (MS)-based metabolomics approaches is an attractive solution for human studies representing a less-invasive procedure compared to phlebotomy with the additional potential for remote sample collection. However, as we recently demonstrated, VAMS samples require long-term storage at -80 °C. This study investigated the stability of VAMS samples during short-term storage and compared the metabolome obtained from capillary blood collected from the fingertip to those of plasma and venous blood from 22 healthy volunteers. Our results suggest that the blood metabolome collected by VAMS samples is stable at room temperature only for up to 6 h requiring subsequent storage at -80 °C to avoid significant changes in the metabolome. We also demonstrated that capillary blood provides better coverage of the metabolome compared to plasma enabling the analysis of several intracellular metabolites presented in red blood cells. Finally, this work demonstrates that with the appropriate pre-analytical protocol capillary blood can be successfully used for untargeted metabolomics studies.

Volumetric Absorptive Microsampling to Enhance the Therapeutic Drug Monitoring of Tacrolimus and Mycophenolic Acid: A Systematic Review and Critical Assessment

BACKGROUND

Volumetric absorptive microsampling (VAMS) is an emerging technique that may support multisample collection to enhance therapeutic drug monitoring in solid organ transplantation. This review aimed to assess whether tacrolimus and mycophenolic acid can be reliably assayed using VAMS and to identify knowledge gaps by providing granularity to existing analytical methods and clinical applications.

METHODS

A systematic literature search was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The PubMed, Embase, and Scopus databases were accessed for records from January 2014 to April 2022 to identify scientific reports on the clinical validation of VAMS for monitoring tacrolimus and mycophenolic acid concentrations. Data on the study population, sample sources, analytical methods, and comparison results were compiled.

RESULTS

Data from 12 studies were collected, including 9 studies pertaining to tacrolimus and 3 studies on the concurrent analysis of tacrolimus and mycophenolic acid. An additional 14 studies that provided information relevant to the secondary objectives (analytical validation and clinical application) were also included. The results of the clinical validation studies generally met the method agreement requirements described by regulatory agencies, but in many cases, it was essential to apply correction factors.

CONCLUSIONSS

Current evidence suggests that the existing analytical methods that use VAMS require additional optimization steps for the analysis of tacrolimus and mycophenolic acid. The recommendations put forth in this review can help guide future studies in achieving the goal of improving the care of transplant recipients by simplifying multisample collection for the dose optimization of these drugs.

Current Status of Therapeutic Drug Monitoring in Mental Health Treatment: A Review

Therapeutic drug monitoring (TDM) receives growing interest in different psychiatric clinical settings (emergency, inpatient, and outpatient services). Despite its usefulness, TDM remains underemployed in mental health. This is partly due to the need for evidence about the relationship between drug serum concentration and efficacy and tolerability, both in the general population and even more in subpopulations with atypical pharmacokinetics. This work aims at reviewing the scientific literature published after 2017, when the most recent guidelines about the use of TDM in mental health were written. We found 164 pertinent records that we included in the review. Some promising studies highlighted the possibility of correlating early drug serum concentration and clinical efficacy and safety, especially for antipsychotics, potentially enabling clinicians to make decisions on early laboratory findings and not proceeding by trial and error. About populations with pharmacokinetic peculiarities, the latest studies confirmed very common alterations in drug blood levels in pregnant women, generally with a progressive decrease over pregnancy and a very relevant dose-adjusted concentration increase in the elderly. For adolescents also, several drugs result in having different dose-related concentration values compared to adults. These findings stress the recommendation to use TDM in these populations to ensure a safe and effective treatment. Moreover, the integration of TDM with pharmacogenetic analyses may allow clinicians to adopt precise treatments, addressing therapy on an individual pharmacometabolic basis. Mini-invasive TDM procedures that may be easily performed at home or in a point-of-care are very promising and may represent a turning point toward an extensive real-world TDM application. Although the highlighted recent evidence, research efforts have to be carried on: further studies, especially prospective and fixed-dose, are needed to replicate present findings and provide clearer knowledge on relationships between dose, serum concentration, and efficacy/safety.

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’.

Dried Volumetric Microsampling Approaches for the Therapeutic Drug Monitoring of Psychiatric Patients Undergoing Clozapine Treatment

Clozapine is one of the most widely used second-generation antipsychotic drugs (SGAs) for the treatment of schizophrenia. Despite advantages over first-generation drugs, clozapine still shows significant side effects and interindividual variations in efficacy. In order to ensure frequent therapeutic drug monitoring (TDM) and improve the compliance of psychiatric patients undergoing clozapine treatment, two novel dried microsampling approaches based on whole blood and plasma volumetric absorptive microsampling (b-VAMS and p-VAMS) and microfluidic generated-dried blood spot technology (mfDBS) were developed and coupled to HPLC with electrochemical detection (ED). The proposed miniaturized strategies by means of VAMS and microfluidic channel-based devices provide several advantages in terms of collection, storage, and handling compared to classical blood and plasma processing. Satisfactory validation results were obtained for all microsampling platforms, with mean extraction yields >85.1%, precision as relative standard deviation (RSD) < 5.1%, and stability < 4.5% analyte loss after 30 days for p-VAMS; mean extraction yields > 83.4%, precision RSD < 5.4%, and stability < 4.6% analyte loss after 30 days for b-VAMS, and mean extraction yields > 74.0%, precision RSD < 5.6%, and stability < 4.9% analyte loss after 30 days for mfDBS. The original microsampling methodologies have been successfully applied to the blood and plasma collected from five psychiatric patients for the monitoring of the levels of clozapine and its main metabolites, providing robust and reliable quali-quantitative results. Comparisons between results of the two dried microsampling technologies with those obtained by classic fluid plasma analysis were in good agreement and have demonstrated that the proposed miniaturized approaches could be suitable for TDM purposes.

Ion-Channel Antiepileptic Drugs: An Analytical Perspective on the Therapeutic Drug Monitoring (TDM) of Ezogabine, Lacosamide, and Zonisamide

The term seizures includes a wide array of different disorders with variable etiology, which currently represent one of the most important classes of neurological illnesses. As a consequence, many different antiepileptic drugs (AEDs) are currently available, exploiting different activity mechanisms and providing different levels of performance in terms of selectivity, safety, and efficacy. AEDs are currently among the psychoactive drugs most frequently involved in therapeutic drug monitoring (TDM) practices. Thus, the plasma levels of AEDs and their metabolites are monitored and correlated to administered doses, therapeutic efficacy, side effects, and toxic effects. As for any analytical endeavour, the quality of plasma concentration data is only as good as the analytical method allows. In this review, the main techniques and methods are described, suitable for the TDM of three AEDs belonging to the class of ion channel agents: ezogabine (or retigabine), lacosamide, and zonisamide. In addition to this analytical overview, data are provided, pertaining to two of the most important use cases for the TDM of antiepileptics: drug–drug interactions and neuroprotection activity studies. This review contains 146 references.

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.

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.

Quantitative microsampling for bioanalytical applications related to the SARS-CoV-2 pandemic: Usefulness, benefits and pitfalls

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SARS-CoV-2 emergency sparks the need for diagnostic and therapeutic actions.

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Microsampling is emerging in as an attractive alternative to traditional sampling.

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Advantages and challenges of the main microsampling techniques are reported.

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Available microsampling applications of interest for SARS-CoV-2 are described.

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Most useful information for researchers and clinicians are gathered and provided.

The multiple pathological effects of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, and its total novelty, mean that currently a lot of diagnostic and therapeutic tools, established and tentative alike, are needed to treat patients in a timely, effective way. In order to make these tools more reliable, faster and more feasible, biological fluid microsampling techniques could provide many advantages. In this review, the most important microsampling techniques are considered (dried matrix spots, volumetric absorptive microsampling, microfluidics and capillary microsampling, solid phase microextraction) and their respective advantages and disadvantages laid out. Moreover, currently available microsampling applications of interest for SARS-CoV-2 therapy are described, in order to make them as much widely known as possible, hopefully providing useful information to researchers and clinicians alike.