Dried Blood Spots-A Platform for Therapeutic Drug Monitoring (TDM) and Drug/Disease Response Monitoring (DRM)

Blood self-sampling devices: innovation, interpretation and implementation in total lab automation

The introduction of the vacuum tube in 1949 revolutionized blood collection, significantly improving sample quality and patient comfort. Over the past 75 years, laboratory diagnostics have evolved drastically, from manual to automated processes, reducing required test volumes by over 1,000 times. Despite these advancements, venous blood collection presents logistical challenges, including centralized scheduling and a large volume of biological waste due to the imbalance between the needed blood volume (often very little) and the collected volume (often in excess). The COVID-19 pandemic further emphasized the need for decentralized healthcare solutions and patient empowerment. Capillary blood collection, widely used in point-of-care testing, offers a promising alternative, particularly for patients facing frequently, or difficulties with, venous sampling. The Leiden University Medical Center in the Netherlands experienced a 15 % reduction in volume of laboratory tests during and after the pandemic, attributed to patient preference for local blood collection and testing. To address these challenges, self-sampling devices are emerging, empowering patients and streamlining sample logistics. However, challenges such as cost, transportation regulations, and sample volume adequacy persists. Robust devices tailored for total lab automation and sustainable practices are crucial for widespread adoption. Despite hurdles, the integration of self-sampling into diagnostic processes is inevitable, heralding a shift towards patient-centered, proactive healthcare. Practical recommendations include robust device design, ease of use, affordability, sustainability, sufficient quality and acceptability by seamless integration into laboratory workflows. Although obstacles remain, self-sampling represents the future of laboratory diagnostics, offering convenience, cost-effectiveness, interoperability and patient empowerment.

Dried blood spot LC-MS/MS quantification of voclosporin in renal transplant recipients using volumetric dried blood spot sampling

Voclosporin is a potent immunosuppressive agent currently approved for treating active lupus nephritis. Based on its potential antiviral activity, it has also been investigated as immunosuppressive agent in an investigator-initiated study in SARS-CoV2 positive kidney transplant recipients. As with many immunosuppressive agents, optimizing dosing regimens to achieve therapeutic efficacy while minimizing toxicity remains a critical challenge in clinical practice. To prevent organ rejection as well as infections, the prescribed immunosuppression needs to be well balanced. Dried blood spot (DBS) sampling has enabled development of remote voclosporin therapeutic drug monitoring. Here, we report on the development and analytical validation of a liquid chromatography tandem mass spectrometry (LC-MS/MS) assay for quantification of voclosporin in dried blood spots. Method development was based on previously developed assays for the quantification of tacrolimus, everolimus, sirolimus, cyclosporin, mycophenolic acid, creatinine and iohexol in DBS and voclosporin in whole blood using LC-MS/MS. HemaXis™ volumetric blood spot devices were used for sample collection. The sample purification was based on the extraction of voclosporin from the DBS samples. Stable isotopically labeled voclosporin-D4 was used as an internal standard prior to sample purification. Bland Altman and Passing bablok analysis were performed for cross validation between whole blood and DBS samples. The method was successfully validated following the current ICH M10 guidelines. The dynamic range for the analyte was 10-600 µg/L with an excellent mean coefficient of correlation of 0.9978. The within run and between run precision and accuracy were both within the acceptance criteria. The cross-validation against the whole blood method shows that the quantified voclosporin results are promising. This developed dried blood spot LC-MS/MS method was successfully validated and provides an easy, efficient workflow for therapeutic drug monitoring in kidney transplant patients or remote pharmacokinetic studies in lupus nephritis patients treated with voclosporin.

GC-MS uncovers unique metabolic markers of drug-resistant epilepsy in capillary but not venous dried blood spots

This study compared the effectiveness of capillary dried blood spots (DBS) versus venous DBS in detecting metabolic changes related to drug-resistant epilepsy (DRE). DBS samples were collected from 142 epilepsy patients (58 drug-resistant, 84 drug-responsive) via venipuncture or fingerstick capillary sampling. Metabolomic analysis using gas chromatography-mass spectrometry compared DBS metabolite profiles between the two groups. While venous DBS profiles showed no distinct patterns, capillary DBS profiles revealed clustering patterns in principal components analysis, with the first two principal components explaining 14.5 %, and 13.5 % of the total variance, respectively. Orthogonal PLS-DA confirmed group discrimination (R2Y=0.989, Q2=0.742). Drug-resistant patients exhibited elevated capillary DBS levels of glutamine, pyruvic acid, and serine, and decreased palmitic acid compared to drug-responsive patients. Pathway analysis revealed disruptions in amino acid metabolism, neurotransmission, and cellular energy regulation. Elevated glutamine levels may contribute to an imbalance between excitatory glutamate and inhibitory GABA neurotransmission, key factors in epileptogenesis and drug resistance. Capillary DBS, likely enriched with arterial blood supply to the brain, appears to better capture central nervous system metabolic disturbances compared to venous DBS containing systemic contributions. This minimally invasive capillary DBS approach offers effective metabolic profiling of brain conditions like DRE, for monitoring disease progression and treatment response, enhancing personalized patient management in epilepsy.

Determination of Antiepileptics in Biological Samples-A Review

Epilepsy remains a disease that affects many people around the world. With the development of new drugs to treat this condition, the importance of therapeutic drug monitoring continues to rise and remains a challenge for the medical community. This review article explores recent advances in the detection of antiepileptic drugs across various sample types commonly used for drug monitoring, with a focus on their applications and impact. Some of these new methods have proven to be simpler, greener, and faster, making them easier to apply in the context of therapeutic drug monitoring. Additionally, besides the classic use of blood and its derivatives, there has been significant research into the application of alternative matrices due to their ease of sample collection and capacity to reflect drug behavior in blood. These advances have contributed to increasing the efficacy of therapeutic drug monitoring while enhancing its accessibility to the population.

Utility of an Archival Dried Blood Spot (DBS) Collection from HIV-Infected Individuals with and without Cancer in a Resource-Limited Setting

The frequency of virus-associated cancers is growing worldwide, especially in resource-limited settings. One of the biggest challenges in cancer research among people living with HIV (PLWH) has been understanding how infection with both HIV and Kaposi sarcoma-associated herpesvirus (KSHV) promotes the pathogenesis of Kaposi sarcoma (KS), the most common cancer among PLWH worldwide and a significant public health problem in regions with high prevalence of HIV such as Sub-Saharan Africa (SSA). The AIDS and Cancer Specimen Resource (ACSR) provides samples for research, including dried blood spots (DBS) that were collected from large clinical epidemiology studies of KSHV and KS in PLWH conducted more than a decade ago in SSA. Here, we validated the quality of DNA derived from DBS samples from SSA studies and provided evidence of quantitative recovery of inflammatory cytokines using these DBS samples through comparison with paired frozen plasma. Significant differences in DNA, protein yields, and inflammatory biomarker levels were also observed between PLWH with/without KS. Establishing the fitness of DBS samples for studies of KS pathogenesis extends the number of projects that can be supported by these ACSR special collections and provides evidence that DBS collection for future KS research is a practical option in resource-limited settings.

Diagnostic Value of Menstrual Blood Lipidomics in Endometriosis: A Pilot Study

Endometriosis is a prevalent chronic inflammatory disease characterized by a considerable delay between initial symptoms and diagnosis through surgery. The pressing need for a timely, non-invasive diagnostic solution underscores the focus of current research efforts. This study examines the diagnostic potential of the menstrual blood lipidome. The lipid profile of 39 samples (23 women with endometriosis and 16 patients in a control group) was acquired using reverse-phase high-performance liquid chromatography-mass spectrometry with LipidMatch processing and identification. Profiles were normalized based on total ion counts. Significant differences in lipids were determined using the Mann-Whitney test. Lipids for the diagnostic model, based on logistic regression, were selected using a combination of variance importance projection filters and Akaike information criteria. Levels of ceramides, sphingomyelins, cardiolipins, triacylglycerols, acyl- and alkenyl-phosphatidylethanolamines, and alkenyl-phosphatidylcholines increased, while acyl- and alkyl-phosphatidylcholines decreased in cases of endometriosis. Plasmenylphosphatidylethanolamine PE P-16:0/18:1 and cardiolipin CL 16:0_18:0_22:5_22:6 serve as marker lipids in the diagnostic model, exhibiting a sensitivity of 81% and specificity of 85%. The diagnostic approach based on dried spots of menstrual blood holds promise as an alternative to traditional non-invasive methods for endometriosis screening.

Preanalytical Stability of 13 Antibiotics in Biological Samples: A Crucial Factor for Therapeutic Drug Monitoring

The stability of antibiotic preanalytical samples is a critical factor in therapeutic drug monitoring (TDM), a practice of undoubted importance for the proper therapeutic use of antibiotics, especially in complex management patients, such as pediatrics. This review aims to analyze the data in the literature regarding the preanalytical stability of some of the antibiotics for which TDM is most frequently requested. The literature regarding the preanalytical stability of amikacin, ampicillin, cefepime, ceftazidime, ciprofloxacin, daptomycin, gentamicin, levofloxacin, linezolid, meropenem, piperacillin, teicoplanin, and vancomycin in plasma, serum, whole blood, and dried blood/plasma spot samples was analyzed. Various storage temperatures (room temperature, 4 °C, -20 °C, and -80 °C) and various storage times (from 1 h up to 12 months) as well as subjecting to multiple freeze-thaw cycles were considered. The collected data showed that the non-beta-lactam antibiotics analyzed were generally stable under the normal storage conditions used in analytical laboratories. Beta-lactam antibiotics have more pronounced instability, particularly meropenem, piperacillin, cefepime, and ceftazidime. For this class of antibiotics, we suggest that storage at room temperature should be limited to a maximum of 4 h, storage at 2-8 °C should be limited to a maximum of 24 h, and storage at -20 °C should be limited to a maximum of 7 days; while, for longer storage, freezing at -80 °C is suggested.

Magnetic solid-phase extraction-based surface-enhanced Raman spectroscopy for label-free therapeutic drug monitoring of carbamazepine and clozapine in human serum

Determination of antiepileptic drugs and antipsychotics in human serum is significant in individualized drug administration and therapeutic drug monitoring (TDM). In this study, we developed a rapid label-free TDM method for the antiepileptic drug carbamazepine (CBZ) and the antipsychotic clozapine (CLO) in human serum. This detection strategy is based on the combination of surface-enhanced Raman scattering (SERS) and magnetic solid-phase extraction (MSPE). Initially, Fe3O4@SiO2@MIL-101(Fe) nanocomposites were synthesized by the layer-by-layer self-assembly method and characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller, ultraviolet-visible, and Fourier transform infrared analyses. Subsequently, CBZ and CLO were detected in human serum using Fe3O4@SiO2@MIL-101(Fe) as the solid-phase extraction adsorbent and Ag nanoparticles as SERS substrates. The potential of the MSPE-SERS method for the label-free TDM of CBZ and CLO was then investigated. Fe3O4@SiO2@MIL-101(Fe) prevents magnetic particle aggregation and demonstrates rapid magnetic separation capability that simplifies the pretreatment process and reduces interference from complex matrices. Its large surface area can effectively enrich targets in complex matrices, thereby improving the SERS detection sensitivity. The linearity between CBZ and CLO was excellent over the concentration range of 0.1-100 µg/mL (calculated as the intensity of the SERS characteristic peaks of CBZ and CLO at 728 cm and 1054 cm-1, respectively), with correlation coefficients (R2) of 0.9987 and 0.9957, and detection limits of 0.072 and 0.12 µg/mL, respectively. The recoveries of CBZ with CLO ranged from 94.0 % to 105.0 %, and their relative standard deviations were <6.8 %. Compared to other assays, the developed MSPE-SERS method has the advantages of simple sample pretreatment, rapid detection, and good reproducibility, which provides a novel approach for the TDM of other drugs.