Evaluation of dried blood spots as an alternative sampling strategy for 5-fluorouracil monitoring: From method development to clinical application

Therapeutic drug monitoring (TDM) of 5-Fluorouracil (5-FU) is strongly recommended because of its large inter-individual pharmacokinetic variability, narrow therapeutic window, and incidence of toxicity. However, there are several factors that limit the application of TDM in clinical settings. Considering the intrinsic advantages of dried microsamples, such as minimally invasive sampling, analyte stability, and cost-effective logistics, this study aimed to develop a method for the determination of 5-FU in dried blood spots (DBS) using ultra-high liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) and to evaluate its clinical application. Sample preparation was based on an aqueous extraction followed by protein precipitation. Separation was performed in an Acquity UPLC® HSS C18 (150 ×2.1 mm, 1.8 µm), and the mobile phases were water and acetonitrile with 0.5% acetic acid. The total run time was 5.5 min. The method was linear from 100 to 2000 ng/mL, precise (maximum CV% of 7.5%), and accurate (98.3-115.4%). The average recovery was 70%. Blood hematocrit had a minimal impact on the assay. DBS samples were stable for 21 days at 4, 25, and 45 °C. A total of 40 paired samples of plasma, capillary DBS, and venous DBS were analyzed. Median 5-FU concentrations were 444.7, 637.0, and 499.7 ng/mL for plasma, capillary DBS, and venous DBS, respectively. Capillary and plasma concentrations were significantly correlated (r > 0.90), but there was a lack of agreement between the methods, as capillary DBS levels were on average 146% of plasma. Venous DBS corresponded to 110% of the measured plasma concentrations, with a strong correlation (r > 0.97) and agreement between the methods. Our study is the first to report the use of DBS samples to quantify 5-FU. Further studies are needed to establish whether capillary samples can replace plasma.

Metabolite Stability in Archived Neonatal Dried Blood Spots Used for Epidemiologic Research

Epidemiologic studies of low-frequency exposures or outcomes using metabolomics analyses of neonatal dried blood spots (DBS) often require assembly of samples with substantial differences in duration of storage. Independent assessment of stability of metabolites in archived DBS will enable improved design and interpretation of epidemiologic research utilizing DBS. Neonatal DBS routinely collected and stored as part of the California Genetic Disease Screening Program between 1983 and 2011 were used. The study population included 899 children without cancer before age 6 years, born in California. High-resolution metabolomics with liquid-chromatography mass spectrometry was performed, and the relative ion intensities of common metabolites and selected xenobiotic metabolites of nicotine (cotinine and hydroxycotinine) were evaluated. In total, we detected 26,235 mass spectral features across 2 separate chromatography methods (C18 hydrophobic reversed-phase chromatography and hydrophilic-interaction liquid chromatography). For most of the 39 metabolites related to nutrition and health status, we found no statistically significant annual trends across the years of storage. Nicotine metabolites were captured in the DBS with relatively stable intensities. This study supports the usefulness of DBS stored long-term for epidemiologic studies of the metabolome. -Omics-based information gained from DBS may also provide a valuable tool for assessing prenatal environmental exposures in child health research.

A feasible protocol to profile bile acids in dried blood spots from rats using a UHPLC-MS/MS method combining a surrogate matrix

Dried blood spot (DBS) sampling is a promising method for microliter blood sample collection with the advantages of convenient transportation, storage and clinical operations. However, it is challenging to develop an analytical protocol to determine endogenous metabolites, such as bile acids (BAs) in DBSs, due to the low-blood-volume character of DBSs and the complex features of filter paper. Herein, we developed a method of fast ultra-high performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS) to profile and quantify BAs in DBSs. The pretreatment methods were optimized and a two-step solvent addition method, where a small amount of water was firstly added to moisten the DBS and then methanol was added, showed high extraction efficiency for multiple BAs in DBSs. The UHPLC-MS/MS conditions were optimized and 35BAs in different types could be profiled with good resolution and quantified with acceptable precision and accuracy. Preparation of a DBS surrogate matrix without endogenous BAs has been well developed using rat erythrocytes in BSA solution and showed good performance on both the signal suppression/enhancement percentage and parallelism assessment evaluation of three different stable-isotope-labeled (SIL) BAs. The established protocol was successfully applied to profile BAs in DBSs of intrahepatic cholestasis model and healthy control rats with good repeatability. To our knowledge, it is the first time that 35 BAs in DBSs could be well profiled and an appropriate DBS surrogate matrix has been developed. This protocol presents future-oriented applications of DBSs for relevant preclinical studies to profile BAs and probe biomarkers.

Harmonization of distributed multi-center analysis based on dried blood spot reference materials supporting the screening of neonatal inherited metabolic disorders

BACKGROUND

The standardization of quantification data is critical for ensuring the reliability and measurement traceability in the screening of neonatal inherited metabolic disorders. However, the availability of national certified reference materials is limited in China.

METHODS

In this study, we developed a series of dried blood spot (DBS) reference materials containing 9 amino acids (AA) and 10 acylcarnitines (AC) for neonatal screening. Four levels of the reference materials were measured with tandem mass spectrometry (MS/MS) by seven laboratories using different commercial In Vitro Diagnostic Device (IVD) kits. Then, 100 clinical samples were measured using both derivatization and non-derivatization methods by the same laboratory.

RESULTS

We found high homogeneity and stability at all levels of the reference materials, with the coefficient of variation (CV) of the analytes less than 15%. These reference materials can be used to assess the testing capabilities of different laboratories. Our test also revealed that the correction factors (CF) calculated by the reference materials, along with clinical samples, could increase the consistency for different kits.

CONCLUSION

The DBS reference materials proposed in this study provide reliability for the harmonization in multi-center analysis for the screening of neonatal inherited metabolic disorders. And applying our correction method for the screening could improve the data consistency of the DBS samples prepared by different methods.

Dried Blood Spots (DBS): A suitable alternative to using whole blood samples for diagnostic testing of visceral leishmaniasis in the post-elimination era

BACKGROUND

Serum or whole blood collection, processing, transport and storage still present significant challenges in low resource settings where mass surveillance is required to sustain disease elimination. Therefore, in this study, we explored the diagnostic efficacy of dried blood spots (DBS) as a minimally invasive and potentially cost-effective alternative sampling technique to whole blood sampling procedures for subsequent detection of Leishmania donovani antibodies or DNA.

METHODOLOGY AND PRINCIPAL FINDINGS

Archived serum, DNA samples from whole blood of visceral leishmaniasis (VL) cases and healthy controls, and DBS from corresponding cases and controls, were used. Both molecular and serological assays were optimized to detect L. donovani antibodies or DNA in DBS elute and results were compared against those obtained with whole blood. Serological assays (both rK28 ELISA and rK39 ELISA) of DBS samples showed sensitivity and specificity of 100% and had excellent agreement with results from whole blood samples (kappa value ranged from 0.98-1). Bland-Altman analysis of OD values from rK28-ELISA with DBS elute and patients' serum showed an excellent agreement (ICC = 0.9) whereas a good agreement (ICC = 0.8) was observed in the case of rK39-ELISA. However, qPCR and RPA of DBS samples had a diminished sensitivity of 76% and 68%, respectively, and poor agreement was observed with the whole blood samples.

CONCLUSION

Our results demonstrate that DBS offer excellent diagnostic efficiency for serological assays and represent a viable alternative to whole blood sampling procedures.

Developing a Method for Quantifying Meropenem in Children-Volumetric Adsorptive Microsampling Versus Plasma Sampling

BACKGROUND

Meropenem is a carbapenem antibiotic often used in pediatric intensive care units due to its broad spectrum of activity. Therapeutic drug monitoring (TDM) is a useful tool to increase the effectiveness of meropenem by adjusting the dose based on plasma levels; however, the relatively large sample volume required for TDM can limit its use in children. Therefore, this study aimed to determine meropenem concentrations and consequently perform TDM effectively using the smallest possible sample volume. Volumetric absorptive microsampling (VAMS) is a sampling technology developed to collect a small, precise volume of blood. For the applicability of VAMS in TDM, plasma concentrations must be reliably calculated from whole blood (WB) collected by VAMS.

METHODS

VAMS technology using 10 µL of WB was evaluated and compared with EDTA-plasma sampling. High-performance liquid chromatography with UV detection was applied to quantify meropenem in VAMS and plasma samples after the removal of proteins by precipitation. Ertapenem was used as the internal standard. Samples were collected simultaneously from critically ill children receiving meropenem using VAMS and traditional sampling.

RESULTS

It was found that no consistent factor could be determined to calculate meropenem plasma concentrations from the WB, indicating that VAMS was not reliable in the TDM of meropenem. Therefore, to reduce the required sample amount in pediatric patients, a method for quantifying meropenem from 50 µL of plasma with a lower limit of quantification of 1 mg/L was developed and successfully validated.

CONCLUSIONS

A simple, reliable, and low-cost method was established using high-performance liquid chromatography-UV to determine the concentration of meropenem in 50 µL of plasma. VAMS using WB does not seem to be suitable for TDM of meropenem.

Development, optimization and validation of LC-MS/MS method for the determination of DBS GALT enzyme activity

Galactosemia is a carbohydrate metabolism disorder often caused by galactose-1-phosphate uridyl transferase (GALT) deficiency. Detecting GALT deficiency involves measuring intra-erythrocyte enzyme activity. We aimed to create a robust liquid chromatography-mass spectrometry (LC-MS/MS) method to assess GALT activity in dried blood spot (DBS) samples. We validated this method and compared it to the fluorometric approach. We investigated the impact of K2EDTA and lithium heparin tubes on enzyme activity to identify the best sample collection tube. We also assessed the reaction-stopping method. The developed approach employed [13C6]-galactose-1-phosphate as a substrate and UDP-N-acetylglycosamine as an internal standard (IS). The mean ± SD value for GALT activity of DBS samples was determined as 6.37 ± 1.96 μmol/gHb/hour. The linear range was 0.4-50 μM (2.4-310% of normal) in the DBS method. The % coefficient of variation (%CV) values were less than 15 for intra-day and inter-day repeatability studies. Over 90% recovery was achieved in recovery studies, and no ion suppression from matrix was detected. DBS samples were quite stable for 31 days under different storage conditions. Enzyme activity results reported as <3.5 U/g Hb by fluorometric method, were quantitatively determined for even very low concentrations by LC-MS/MS method.

Achieving routine application of dried blood spots for erythropoietin receptor agonist analysis in doping control: low-volume single-spot detection at minimum required performance level

Background: Erythropoietin receptor agonists (ERAs) are substances prohibited in sports and currently monitored in urine and blood. There is a great interest in new matrices like dried blood spots (DBSs). Method: A direct method for the detection of ERAs in DBSs using one single spot of 25 μl has been optimized and validated. Results: Limits of detection close or equal to those required by the World Anti-Doping Agency for serum/plasma samples were achieved, using a volume 20-times lower. All analytes were stable for at least 90 days at room temperature. Conclusion: Method performance was comparable to the requirements established for blood samples and, thus, monitoring of ERAs is reliable in DBSs in the context of doping control.

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

This review provides an overview on the current applications of dried blood spots (DBS) as matrices for therapeutic drug (TDM) and drug or disease response monitoring (DRM). Compared with conventional methods using plasma/serum, DBS offers several advantages, including minimally invasiveness, a small blood volume requirement, reduced biohazardous risk, and improved sample stability. Numerous assays utilising DBS for TDM have been reported in the literature over the past decade, covering a wide range of therapeutic drugs. Several factors can affect the accuracy and reliability of the DBS sampling method, including haematocrit (HCT), blood volume, sampling paper and chromatographic effects. It is crucial to evaluate the correlation between DBS concentrations and conventional plasma/serum concentrations, as the latter has traditionally been used for clinical decision. The feasibility of using DBS sampling method as an option for home-based TDM is also discussed. Furthermore, DBS has also been used as a matrix for monitoring the drug or disease responses (DRM) through various approaches such as genotyping, viral load measurement, assessment of inflammatory factors, and more recently, metabolic profiling. Although this research is still in the development stage, advancements in technology are expected to lead to the identification of surrogate biomarkers for drug treatment in DBS and a better understanding of the correlation between DBS drug levels and drug responses. This will make DBS a valuable matrix for TDM and DRM, facilitating the achievement of pharmacokinetic and pharmacodynamic correlations and enabling personalised therapy.

Smart sampling as the "Spot-on" Method for LC-MS protein analysis from dried blood spots

This perspective explores the feasibility of smart sampling with dried blood spots for the determination of proteins and peptides from human biomatrices using liquid chromatography coupled to mass spectrometry for clinical purposes. The focus is on innovative approaches to transform filter paper from a mere sample carrier to an active element in sample preparation, with the aim of reducing the need for extensive and intensive sample preparation in the conventional sense. Specifically, we discuss the use of modified cellulose to integrate sample preparation at an early stage of sample handling. The use of paper immobilized with either trypsin or monoclonal antibodies for protein digestion and affinity clean-up is discussed as a potential benefit of starting sample preparation instantly at the moment of sampling to optimize time efficiency and enable faster analysis, diagnosis, and follow-up of patients.

Using Mitra sampling to support first-in-human pharmacokinetic evaluations for PF-07059013

Aim: A sensitive and selective method for the determination of PF-07059013 in dried blood collected by Mitra™ tips was developed and qualified from 50 to 50,000 ng/ml. Materials & methods: PF-07059013 is isolated from 10 μl of human dried blood by extraction with methanol and analyzed by HPLC-MS/MS. Results & conclusions: In addition to routine validation elements, impact of hematocrit and Mitra tip's lot-to-lot variation on assay accuracy were evaluated. The qualified method was used in one clinical study with excellent performance. Correlation coefficient between blood concentrations obtained from liquid-incurred blood samples and dried-incurred blood samples is 0.95. Clinical Trial Registration: NCT04323124 (ClinicalTrials.gov).

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

A randomised study of nurse collected venous blood and self-collected dried blood spots for the assessment of cardiovascular risk factors in the Understanding Society Innovation Panel

Dried blood spot (DBS) sample collection has been suggested as a less invasive, cheaper and more convenient alternative to venepuncture, which requires trained personnel, making it a potentially viable approach for self-collection of blood on a large scale. We examine whether participants in a longitudinal survey were willing to provide a DBS sample in different interview settings, and how resulting cardiovascular risk biomarkers compared with those from venous blood to calculate clinical risk. Participants of the Understanding Society Innovation Panel, a representative sample of UK households, were randomly assigned to three modes of interview. Most participants (84%) were interviewed in their allocated mode. Participants (n = 2162) were interviewed by a nurse who collected both a blood sample by venepuncture and a DBS card ('nurse collection') or participants were seen by an interviewer or took part in the survey online to self-collect a DBS card ('self-collection'). All DBS cards were returned in the post after the sample had dried. Lipids (total cholesterol, HDL-cholesterol, triglycerides), HbA1c and C-reactive protein were measured in venous and DBS samples and equivalence was calculated. The resultant values were used to confirm equivalent prevalence of risk of cardiovascular disease in each type of blood sample by mode of participation. Of participants interviewed by a nurse 69% consented to venous blood sample and 74% to a DBS sample, while in the self-collection modes, 35% consented to DBS collection. Demographic characteristics of participants in self-collection mode was not different to those in nurse collection mode. The percentage of participants with clinically raised biomarkers did not significantly differ between type of blood collection (for example, 62% had high cholesterol (> 5 mmol/l) measured by venepuncture and 67% had high cholesterol within the self-collected DBS sample (p = 0.13)). While self-collected DBS sampling had a lower response rate to DBS collected by a nurse, participation did not vary by key demographic characteristics. This study demonstrates that DBS collection is a feasible method of sample collection that can provide acceptable measures of clinically relevant biomarkers, enabling the calculation of population levels of cardiovascular disease risk.

Capillary Electrophoresis with Interchangeable Cartridges for Versatile and Automated Analyses of Dried Blood Spot Samples

A novel concept for highly versatile automated analyses of dried blood spot (DBS) samples by commercial capillary electrophoresis (CE) is presented. Two interchangeable CE cartridges with different fused-silica capillaries were used for the DBS elutions and the DBS eluate analyses, respectively. The application of one CE cartridge with a wide-bore capillary reduced DBS processing times to a minimum (1-2 min per sample) while fitting the other CE cartridge with a narrow-bore capillary served for highly efficient CE analyses. A comprehensive investigation of major variables affecting liquid handling in CE (capillary length, internal diameter, and temperature) was carried out with the aim of optimizing both procedures and enabling their maximum flexibility. The application of two CE cartridges also enabled the employment of CE detectors with different instrumental set-ups and/or principles as was demonstrated by the optical detection of nonsteroidal anti-inflammatory drugs (NSAIDs) and the conductivity detection of amino acids (AAs). The presented methods were optimized for the automated CE analyses of 36 DBS samples formed by a volumetric collection of 5 μL of capillary blood onto Whatman 903 discs and processed by direct in-vial elution using the CE instrument. The precision of liquid transfers for the automated DBS elutions was better than 0.9% and the precision of CE analyses did not exceed 5.1 and 12.3% for the determination of NSAIDs and AAs, respectively. Both methods were linear (R2 ≥ 0.996) over the therapeutic (NSAIDs) and the endogenous (AAs) concentration ranges, had limits of quantification below the typical analyte concentrations in human blood, and achieved sample throughputs of more than 6 DBSs per hour.

A new approach with dried plasma spots: a rapid determination of antidepressants and antipsychotics by fast GC-MS

Background: The increasing prevalence of poisoning cases related to antidepressants and antipsychotics has raised concerns. Methods: To address this issue, a new adaptation of the dried plasma spot technique was developed using a 24-well plate and fast gas chromatography-mass spectrometry. The method involves the optimization of extraction variables and sample preparation, and was successfully validated. Results: The limits of quantitation ranged from 20 to 60 ng/ml, and accuracy ranged from 87.8% to 112.2%. The technique was applied to 102 human plasma samples from suspected poisoning cases, with positivity of 90.2%. Conclusion: This method provides a cheap, easy to implement and fast approach, making it ideal for toxicological emergency laboratories and promoting valuable support for healthcare professionals managing poisoning cases involving antidepressants and antipsychotics.

Volumetric absorptive microsampling as an effective microsampling technique for LC-MS/MS bioanalysis of biomarkers in drug discovery

Aim: Develop and validate a volumetric absorptive microsampling (VAMS)-based LC-MS/MS method to support the bioanalysis of amino acid and carboxylic acid biomarkers in mouse whole blood. Method: Mouse whole blood was collected using a 10 μl VAMS device. The analytes in VAMS were extracted and analyzed using an LC-MS/MS method. Results: The VAMS-based LC-MS/MS assay exhibited a linearity range of 10.0-10,000 ng/ml with acceptable precision and accuracy and consistent recovery. The analyte stability in mouse whole blood VAMS was shown for 7 days at ambient conditions and at -80°C, as well as with three freeze/thaw cycles. Conclusion: A simple and robust VAMS-based LC-MS/MS method was developed and further validated for simultaneous bioanalysis of nine biomarkers in mouse whole blood.

Liquid chromatography with tandem mass spectrometric method for determination of 425 drugs and poisons in dried blood spots and application to forensic cases

PURPOSE

An analytical method using liquid chromatography with tandem mass spectrometry (LC-MS/MS) was established and validated for screening 425 drugs and poisons in dried blood spots (DBSs).

METHODS

Blood (20 μL) was spotted on Whatman FTA™ classic card to prepare DBS sample, then extracted with 150 μL methanol and analyzed by LC-MS/MS using a multiple reaction monitoring method.

RESULTS

The limit of detection of the compounds were 0.1-10 ng/mL. The values for recovery and matrix effect were 40.3-114.9% and 40.2-118.4%, respectively. This method was successfully applied to DBS samples from 105 humans suspected of drug poisoning, which was stored for 3-5 years at room temperature. Thirty-three kinds of drugs, including benzodiazepines, antipsychotics, antidepressants, antipyretic analgesics, non-steroidal anti-inflammatory drugs, antibiotics, antiepileptic drugs, new psychoactive drugs were confirmed in 102 cases, while no compound was detected in the other 3 cases. Estazolam, a benzodiazepine widely used in clinical practice as a sedative, hypnotic, and anti-anxiety drug, was the most frequently detected substance, occurring in 34.2% of the cases.

CONCLUSIONS

Most drugs in DBS could still be detected after storage for 3-5 years, but ambroxol, zopiclone, carbofuran, chlorpyrifos, and valproic acid were not detectable after 3-5 years of storage at room temperature. The components measured in DBS were consistent with those measured in whole blood at the collection time, thereby confirming that DBS samples have the advantage of stable storage at room temperature.

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.

Application of novel plasma separation filter cards for quantification of nucleoside/nucleotide reverse transcriptase inhibitor di/triphosphates in dried blood spots using LC-MS

Background: A rapid and sensitive LC-MS method has been developed and validated for the quantification of nucleoside di/triphosphates using a novel plasma separation card (HemaSep). Materials & methods: Cards were spotted with whole blood and stored at -80°C. Metabolites were extracted using 70:30 MeOH:20% formic acid, followed by weak anion exchange SPE and eluted using a Biobasic-AX column. Quantification was performed using a triple quadrupole mass spectrometer with a calibration range of 1.25-250 pmol/sample. Results: The recovery of metabolites was high (>93%). Precision and accuracy were acceptable and metabolites remained stable on the card after 29 days (stored at ambient temperature). Conclusion: HemaSep dried blood spots are a useful microsampling tool and offer an alternative to liquid plasma as they maintain stability over time.

Development and validation of an LC-MS/MS method to quantify the alcohol biomarker phosphatidylethanol 16:0/18:1 in dried blood spots for clinical research purposes

Phosphatidylethanol (PEth) is a group of phospholipids detectable in red blood cells exclusively following ethanol consumption. The primary PEth analog, PEth 16:0/18:1, has an extended half-life in red cells, providing a long window of detection and tremendous potential for the quantification of cumulative alcohol consumption. We developed and validated an LC/MS-MS method to quantify PEth 16:0/18:1 in dried blood spots (DBS) for clinical research purposes. Method development and validation followed FDA guidance but expanded on prior published methods through the evaluation of additional DBS-specific factors such as sample hematocrit, punch location, and spot volume. This method was applied to the quantification of PEth in participant samples.

Development and validation of a liquid chromatographic-tandem mass spectrometric assay for the quantification of cabotegravir and rilpivirine from dried blood spots

BACKGROUND

Dried blood spots (DBS) have been utilized as a blood plasma alternative for therapeutic drug monitoring and pharmacologic analysis. There are analytical and physiochemical considerations in bridging drug concentrations from plasma to DBS. Recently, the long-acting antiretroviral cabotegravir (CAB) has been approved for HIV prevention, and a co-packaged regimen of long-acting CAB and rilpivirine (RPV) has been approved for HIV treatment. Measurement of these drugs in blood collected as DBS may offer increased capacity and flexibility in translational applications.

METHODS

Whole blood was spiked with CAB and RPV and spotted on DBS cards. Following extraction and addition of isotopically labeled internal standards, samples were subjected to liquid chromatographic-tandem mass spectrometric (LC-MS/MS) analysis. The method was validated according to regulatory recommendations, and the assay was evaluated in remnant samples from an HIV prevention trial in which paired DBS and plasma samples were collected.

RESULTS

DBS CAB and RPV concentrations were linear from 25 to 20,000 ng/mL and 2-2500 ng/mL, respectively. Precision, accuracy, and matrix effect results were acceptable. DBS RPV demonstrated stability under all tested conditions; DBS CAB showed mean biases of - 23.5% when stored at room temperature for 36 days, and - 18.0% at 40 °C and 100% humidity for two days. DBS measurements for CAB and RPV were an average 54.0% and 14.1% lower, respectively, as compared to paired plasma samples. Derived conversion factors of 1.79 and 1.16 were applied to DBS CAB and RPV measurements, respectively, to estimate plasma concentrations. Estimated plasma CAB and RPV concentrations showed mean biases of 2.2% and 0.6%, respectively. In a CAB clinical trial, application of the conversion factor resulted in agreement between estimated plasma CAB concentrations from DBS and plasma CAB concentrations (y = 1.08x - 79.2, r = 0.932; mean bias of -3.2%; 95% CI: -48.2% to 41.9%).

CONCLUSIONS

We developed and validated a novel LC-MS/MS assay for the quantification of CAB and RPV from DBS, and identified conversion factors to estimate plasma concentrations from spotted blood.

Effects of Long-Term Storage on the Biobanked Neonatal Dried Blood Spot Metabolome

Over 2.5 million neonatal dried blood spots (DBS) are stored at the Danish National Biobank. These samples offer extraordinary possibilities for metabolomics research, including prediction of disease and understanding of underlying molecular mechanisms of disease development. Nevertheless, Danish neonatal DBS have been little explored in metabolomics studies. One question that remains underinvestigated is the long-term stability of the large number of metabolites typically assessed in untargeted metabolomics over long time periods of storage. Here, we investigate temporal trends of metabolites measured in 200 neonatal DBS collected over a time course of 10 years, using an untargeted liquid chromatography tandem mass spectrometry (LC-MS/MS) based metabolomics protocol. We found that a majority (71%) of the metabolome was stable during 10 years of storage at -20 °C. However, we found decreasing trends for lipid-related metabolites, such as glycerophosphocholines and acylcarnitines. A few metabolites, including glutathione and methionine, may be strongly influenced by storage, with changes in metabolite levels up to 0.1-0.2 standard deviation units per year. Our findings indicate that untargeted metabolomics of DBS samples, with long-term storage in biobanks, is suitable for retrospective epidemiological studies. We identify metabolites whose stability in DBS should be closely monitored in future studies of DBS samples with long-term storage.

Volumetric Absorptive Microsampling for the Therapeutic Drug Monitoring of Everolimus in Patients Who Have Undergone Liver Transplant

BACKGROUND

Therapeutic drug monitoring (TDM) of everolimus is required to prevent organ rejection in patients who have undergone transplant. Volumetric absorptive microsampling (VAMS) is a minimally invasive method for accurately collecting a small amount of blood from a patient's fingers. This study aimed to assess the applicability of VAMS for TDM of everolimus.

METHODS

VAMS and venous blood samples were collected from 45 liver transplant recipients who had been receiving stable everolimus doses for at least 7 days. Whole blood everolimus concentrations were measured using ultrahigh performance liquid chromatography with tandem mass spectrometry. Deming regression and Bland-Altman analysis were performed to compare everolimus concentrations measured using VAMS (C VAMS ) and venous blood samples (C IV ). The regression coefficient (r 2 ) between C VAMS and C IV was calculated using a linear regression. The effects of the hematocrit and blood sampling time on the difference between C VAMS and C IV were investigated.

RESULTS

Thirty-two participants were included in the final analysis. The Deming regression line was C IV = 1.04 × C VAMS + 0.55 [95% confidence interval (CI) of slope, 0.91-1.18; 95% CI of intercept, -0.05 to 1.16]. C VAMS and C IV were strongly correlated (r 2 = 0.92), with no proportional or constant bias. The mean difference between C VAMS and C IV was -0.79 ng/mL, with the 95% limit of agreement ranging from -2.55 to 0.97 ng/mL in a Bland-Altman plot. No effect of the hematocrit or blood sampling time was observed.

CONCLUSIONS

VAMS and venous blood sampling showed good agreement for the measurement of whole blood everolimus concentrations. Less invasive VAMS can substitute for more invasive venous blood sampling in the TDM of everolimus in liver transplant patients.

Development of a fast and robust liquid chromatography-mass spectrometry-based metabolomics analysis method for neonatal dried blood spots

Dried blood spot (DBS) samples have been widely used in many fields including newborn screening, with the advantages in transportation, storage and non-invasiveness. The DBS metabolomics research of neonatal congenital diseases will greatly expand the understanding of the disease. In this study, we developed a liquid chromatography-mass spectrometry-based method for neonatal metabolomics analysis of DBS. The influences of blood volume and chromatographic effects on the filter paper on metabolite levels were studied. The levels of 11.11 % metabolites were different between 75 μL and 35 μL of blood volumes used for DBS preparation. Chromatographic effects on the filter paper occurred in DBS prepared with 75 μL whole blood and 6.67 % metabolites had different MS responses when central disks were compared with outer disks. The DBS storage stability study showed that compared with - 80 °C storage, storing at 4 °C for 1 year had obvious influences on more than half metabolites. Storing at 4 °C and - 20 °C for short term (< 14 days) and - 20 °C for longer term (1 year) had less influences on amino acids, acyl-carnitines and sphingomyelins, but greater influences on partial phospholipids. Method validation showed that this method has a good repeatability, intra-day and inter-day precision and linearity. Finally, this method was applied to investigate metabolic disruptions of congenital hypothyroidism (CH), metabolic changes of CH newborns were mainly involved in amino acid metabolism and lipid metabolism.

Development and validation of an LC-MS/MS assay for the quantitative analysis of alprazolam, α-hydroxyalprazolam and hydrocodone in dried blood spots

Dried blood spot (DBS) has been used as an alternative matrix in drug testing. In forensic testing it offers enhanced stability of analytes and ease of storage that requires minimal space. This is compatible with long term archiving of large numbers of samples for future investigation. We employed liquid chromatography-tandem mass spectrometry (LC-MS/MS) to quantify alprazolam, α-hydroxyalprazolam, and hydrocodone in a DBS sample that has been stored for 17 years. We achieved linear dynamic ranges (0.1-50 ng/mL) that capture wide ranges of concentration of the analytes below and above their reported reference ranges, and limits of detection (0.05 ng/mL) of 40-100X lower than the lower limit of the analyte's reference ranges. The method was validated according to FDA and CLSI guidelines and successfully confirmed and quantified alprazolam and α-hydroxyalprazolam in a forensic DBS sample.