Accuracy of cyclosporin measurements made in capillary blood samples obtained by skin puncture

Clinical Bridging Studies and Modeling Approach for Implementation of a Patient Centric Sampling Technique in Padsevonil Clinical Development

Volumetric absorptive microsampling (VAMS) techniques have gained popularity these last years as innovative tool for collection of blood pharmacokinetic (PK) samples in clinical trials as they offer many advantages over dried blood spot and conventional venous blood sampling. The use of Mitra®, a blood collection device based on volumetric absorptive microsampling (VAMS) technology, was implemented during clinical development of padsevonil (PSL), an anti-seizure medication (ASM) candidate. The present study describes the approach used to bridge plasma (obtained from conventional venous blood sampling) and blood exposures (obtained with Mitra®) to support the use of Mitra as sole blood PK sampling method in clinical trials. Paired blood (using Mitra®) and plasma samples (using conventional venous blood sampling) were collected in healthy volunteers as well as in patients with epilepsy. PSL concentration in plasma and blood were analyzed using different approaches which included evaluation of blood-to-plasma ratios (B/P) over time, linear regression, Bland-Altman analysis as well as development of a linear-mixed effect model based on clinical pharmacology studies. Results showed that the observed in vivo B/P and the measured bias between the 2 collection methods were consistent with the measured in vitro B/P. Graphical analysis demonstrated a clear time effect on the B/P which was confirmed in the linear mixed effect model with sampling time identified as significant covariate. Finally, the built-in model was validated using independent datasets and was shown to adequately predict plasma concentration based on blood concentration with a mean bias of less than 9% (predicted versus observed plasma concentration).

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.

Alternative and promising targets of biochemical analysis in sport (review of literature)

Current literature review provides an evaluation of advantages and limitations of biochemical control objects representing functional state of athletes as well as the outlook for using alternative targets regarding sports medicine. Traditionally, invasive procedures (venous blood collection, muscle biopsy) have been known as the gold standard for analyzing a wide range of biomarkers which could be employed as effective diagnostic tools to control the course of adaptation processes, monitor performance, overtraining and physical well-being of athletes, but these techniques are painful, time-consuming and place demands on storage and shipment. In this behalf finding an alternative objects for biochemical research that does not have disadvantages given above is the question of present interest. Saliva and dry blood spots (DBS) could serve as equally informative and promising targets for monitoring athletes' condition. The non-invasive nature of saliva collection allows to shorten sample collection time, reduce stress hormones levels and possible infection contamination. Moreover, collecting saliva process does not require special equipment and trained medical staff which is particularly important when athletes are at training camps. The DBS method has successfully proven itself with regard to neonatal screening and pharmacokinetics studies. Its key benefits are simplicity, small volume of bioliquid, enhanced stability of adsorbed biomarkers on the card surface, lack of special storage and transportation requirements and low costs for samples shipment to the laboratory. Taken together outlined advantages will provide the opportunity to increase the frequency of biomaterial collection to perform selective observation of training loads effects on various systems of athletes' body. The combination of DBS with immunochemical and mass-spectrometric approaches could serve as an efficient instrument to investigate the role of various biomarkers in monitoring the functional state of athletes. We searched for articles in MedLine database with the key words «dry blood spots», «saliva», «sports medicine», «sample collection», «sports biochemistry».

Volumetric Microsampling of Capillary Blood Spot vs Whole Blood Sampling for Therapeutic Drug Monitoring of Tacrolimus and Cyclosporin A: Accuracy and Patient Satisfaction

BACKGROUND

Immunosuppressant therapeutic drug monitoring (TDM) usually requires outpatient travel to hospitals or phlebotomy sites for venous blood collection; however Mitra® Microsampling Device (MSD) sampling could allow self-collection and shipping of samples to a laboratory for analysis. This study examined the feasibility of using volumetric microsampling by MSD for TDM of tacrolimus (TaC) and cyclosporin A (CsA) in transplant patients, along with their feedback on the process.

METHODS

MSD was used to collect TaC and CsA from venous (VB) or capillary (CB) blood. The MSDs were rehydrated, extracted, and analyzed using on-line solid phase extraction coupled to tandem mass spectrometry (SPE-MS/MS). We report an abbreviated method validation of the MSD including: accuracy, precision, linearity, carry-over, and stability using residual venous whole blood (VB) samples. Subsequent clinical validation compared serially collected MSD + CB against VB (200 µL) from transplant patients.

RESULTS

Accuracy comparing VB vs. MSD+VB showed high clinical concordance (TaC = 89% and CsA = 98%). Inter- and intra-precision was ≤11.5 %CV for TaC and CsA. Samples were stable for up to 7 days at room temperature with an average difference of <10%. Clinical validation with MSD+CB correlated well with VB for CsA (slope = 0.95, r2 = 0.88, n = 47) and TaC (slope = 0.98, r2 = 0.82, n = 49). CB vs. VB gave concordance of 94% for CsA and 79% for TaC. A satisfaction survey showed 82% of patients preferred having the capillary collection option.

CONCLUSION

Transplant patients favored having the ability to collect capillary samples at home for TaC/CsA monitoring. Our results demonstrate good concordance between MSD+CB and VB for TaC and CsA TDM, but additional studies are warranted.

Multiplex Analysis of 230 Medications and 30 Illicit Compounds in Dried Blood Spots and Urine

Drugs of abuse and medication reconciliation testing can benefit from analysis methods capable of detecting a broader range of drug classes and analytes. Mass spectrometry analysis of a wide variety of commonly prescribed medications and over-the-counter drugs per sample also allows for application of a drug-drug interaction (DDI) algorithm to detect adverse drug reactions. In order to prevent adulteration of commonly collected clinical samples such as urine, dried blood spots (DBS) present a reliable alternative. A novel method is described for qualitative and quantitative multiplex analysis of 230 parent drugs, 30 illicit drugs and 43 confirmatory metabolites by HPLC-MS-MS This method is applicable to DBS specimens collected by volumetric absorptive microsamplers and confirmable in urine specimens. A patient cohort (n = 67) providing simultaneous urine specimens and DBS resulted in 100% positive predictive values of medications or illicits confirmed by detection of a parent drug and/or its metabolite during routine medication adherence analysis. An additional 5,508 DBS specimens screened (n = 5,575) showed 5,428 (97%) with an inconsistent positive compared to the provided medication list (including caffeine, cotinine or ethanol metabolites), 29 (0.5%) with no medication list and no unexpected positive results (consistent negative) and 22 (0.4%) showed all positive results matching the provided medication list (consistent positive). A DDI algorithm applied to all positive results revealed 17% with serious and 56% with moderate DDI warnings. Comprehensive DBS analysis proves a reliable alternative to urine drug testing for extended medication reconciliation, with the added advantage of detecting DDIs.

Point-of-care measurement of clozapine concentration using a finger-stick blood sample

BACKGROUND

The use of clozapine demands regular monitoring of clozapine plasma concentrations and of white blood cell parameters. The delay between sending blood samples for analysis and receiving the results hinders clinical care. Point-of-care testing (POCT) can provide drug assay results within a few minutes.

AIM

This study aimed to investigate the utility of a novel point-of-care device that can measure clozapine concentrations using capillary blood samples collected via a finger stick.

METHOD

During a five-week period starting in June 2019 eligible patients were asked to provide a finger-stick capillary sample in addition to their usual venous blood sample. Samples were analysed by the novel point-of-care device and by the standard laboratory method. Capillary blood samples were tested by the MyCare™ Insite POCT analyser, and a quantitative measurement of clozapine concentration was provided within six minutes.

RESULTS

A total of 309 patients agreed to measurements by the two methods. Analysis revealed clozapine concentrations in venous blood as determined by the laboratory method ranged from 20 to 1310 ng/mL and by POCT from 7 to 1425 ng/mL. There was a strong positive correlation (R = 0.89) between the results from the venous and the capillary sample methods. The slope of the association between standard assay and MyCare™ Insite was 1.0 with an intercept of -21 ng/mL, indicating minimal bias.

CONCLUSION

Clozapine concentrations can be accurately measured at the point of care using capillary blood samples collected via a finger stick. This approach may be more acceptable than venous sampling to patients and, with almost instant results available, more useful to clinicians.

Comparison of Capillary and Venous Drug Concentrations After Administration of a Single Dose of Risperidone, Paliperidone, Quetiapine, Olanzapine, or Aripiprazole

Risperidone, paliperidone, quetiapine, olanzapine, and aripiprazole are antipsychotic drugs approved for treating various psychiatric disorders, including schizophrenia. The objective of this randomized, parallel‐group, open‐label study was to compare finger‐stick‐based capillary with corresponding venous whole‐blood and plasma concentrations for these drugs after administration of a single dose to healthy volunteers. All whole‐blood and plasma drug concentrations were measured with validated liquid chromatography–tandem mass spectrometry methods. Capillary and venous concentrations (both in plasma and whole blood) were in close agreement, although a time‐dependent difference was observed, most obviously for olanzapine and paliperidone, with slightly higher capillary versus venous drug concentrations during the first hours after administering a single dose. The observed difference between capillary and venous plasma drug concentrations is expected not to be relevant in clinical practice, considering the wide window of therapeutic concentrations and the wide range of drug concentrations in the patient population for a given dose. Based on these results, finger‐stick‐based capillary drug concentrations have been shown to approximate venous drug concentrations.

Human Immunodeficiency Virus (HIV)-Infected Patients Accept Finger Stick Blood Collection for Point-Of-Care CD4 Testing

Introduction

HIV-infected patients require antiretroviral treatment for life. To improve access to care, CD4 enumeration and viral load tests have been redesigned to be used as point-of-care techniques using finger-stick blood. Accurate CD4 counting in capillary blood requires a free flowing blood drop that is achieved by blade incision. The aim of this study was to assess the attitude of the patients toward blade-based finger-stick blood donation.

Methods

Four hundred and ninety-nine patients were included (299 patients from South Africa and 200 from Belgium). They completed a questionnaire to express their preference for finger stick or venipuncture, after undergoing both. The South African patient cohort was divided in two groups, receiving either single or multiple finger stick for CD4 and other HIV-related tests. The Belgian patients received a single finger stick for CD4 testing, and were asked to respond directly and again after two days.

Results

The majority of the patients preferred the finger stick to the venipuncture. The perceived pain using the blade was superior to a small needle, but similar to a large needle. They preferred up to three finger sticks over one venipuncture. Up to 30% of the patients changed their mind over two days. The main reason for choosing a finger stick was continued bleeding after venipuncture. The most cited objection to finger stick was pain/soreness.

Conclusion

Patient perceptions support the implementation of donating capillary blood with blade-based finger stick during CD4 point-of-care testing.

Comparison of Capillary and Venous Plasma Drug Concentrations After Repeated Administration of Risperidone, Paliperidone, Quetiapine, Olanzapine, or Aripiprazole

Quantification of blood levels of antipsychotic drugs may be useful for managing medication therapy. This open‐label, parallel‐group study was performed to compare finger‐stick‐based capillary with corresponding venous plasma concentrations for risperidone, paliperidone, quetiapine, olanzapine, and aripiprazole and their major metabolites after repeated dosing in patients with schizophrenia or related illnesses. Finger‐stick‐based capillary and venous blood samples were collected at various times within a dosing interval. All drug concentration measurements in the derived plasma samples were performed with validated liquid chromatography–tandem mass spectrometry methods. Finger‐stick‐based capillary and venous plasma drug concentrations after repeated dosing were generally similar. Olanzapine capillary plasma concentrations, however, were on average approximately 20% higher than venous concentrations, with a trend for a relatively greater difference occurring shortly after dosing. In addition, smaller capillary–venous differences were observed for extended‐release and long‐acting intramuscular formulations and for aripiprazole, a drug with a long half‐life, compared with drugs administered as an immediate‐release formulation (risperidone, olanzapine). After repeated dosing, plasma derived from finger‐stick‐based blood was observed to be predictive of the venous concentrations. Capillary sampling may be an appropriate alternative to venous sampling to readily evaluate systemic drug concentrations.

The use of mass spectrometry to analyze dried blood spots

Dried blood spots (DBS) typically consist in the deposition of small volumes of capillary blood onto dedicated paper cards. Comparatively to whole blood or plasma samples, their benefits rely in the fact that sample collection is easier and that logistic aspects related to sample storage and shipment can be relatively limited, respectively, without the need of a refrigerator or dry ice. Originally, this approach has been developed in the sixties to support the analysis of phenylalanine for the detection of phenylketonuria in newborns using bacterial inhibition test. In the nineties tandem mass spectrometry was established as the detection technique for phenylalanine and tyrosine. DBS became rapidly recognized for their clinical value: they were widely implemented in pediatric settings with mass spectrometric detection, and were closely associated to the debut of newborn screening (NBS) programs, as a part of public health policies. Since then, sample collection on paper cards has been explored with various analytical techniques in other areas more or less successfully regarding large-scale applications. Moreover, in the last 5 years a regain of interest for DBS was observed and originated from the bioanalytical community to support drug development (e.g., PK studies) or therapeutic drug monitoring mainly. Those recent applications were essentially driven by improved sensitivity of triple quadrupole mass spectrometers. This review presents an overall view of all instrumental and methodological developments for DBS analysis with mass spectrometric detection, with and without separation techniques. A general introduction to DBS will describe their advantages and historical aspects of their emergence. A second section will focus on blood collection, with a strong emphasis on specific parameters that can impact quantitative analysis, including chromatographic effects, hematocrit effects, blood effects, and analyte stability. A third part of the review is dedicated to sample preparation and will consider off-line and on-line extractions; in particular, instrumental designs that have been developed so far for DBS extraction will be detailed. Flow injection analysis and applications will be discussed in section IV. The application of surface analysis mass spectrometry (DESI, paper spray, DART, APTDCI, MALDI, LDTD-APCI, and ICP) to DBS is described in section V, while applications based on separation techniques (e.g., liquid or gas chromatography) are presented in section VI. To conclude this review, the current status of DBS analysis is summarized, and future perspectives are provided.

Alternative matrices for therapeutic drug monitoring of immunosuppressive agents using LC-MS/MS

Immunosuppressive drugs used in solid organ transplants typically have narrow therapeutic windows and high intra- and intersubject variability. To ensure satisfactory exposure, therapeutic drug monitoring (TDM) plays a pivotal role in any successful posttransplant maintenance therapy. Currently, recommendations for optimum immunosuppressant concentrations are based on blood/plasma measurements. However, they introduce many disadvantages, including poor prediction of allograft survival and toxicity, a weak correlation with drug concentrations at the site of action and the invasive nature of the sample collection. Thus, alternative matrices have been investigated. This paper reviews tandem-mass spectrometry (LC-MS/MS) methods used for the quantification of immunosuppressant drugs utilizing nonconventional matrices, namely oral fluids, fingerprick blood and intracellular and intratissue sampling. The advantages, disadvantages and clinical application of such alternative mediums are discussed. Additionally, sample extraction techniques and basic chromatography information regarding these methods are presented in tabulated form.

Agreement between fingertip-capillary and antecubital-venous appetite-related peptides

This study examined the agreement between fingertip-capillary and antecubital-venous measures of appetite-related peptides. Simultaneous fingertip-capillary and antecubital-venous blood samples were collected from 19 participants. The samples were obtained at baseline, 30, 60, 90, and 120 min following breakfast for the determination of plasma GLP17-36, glucagon, insulin and leptin. Between-day reproducibility of fingertip-capillary-derived estimates was assessed in 18 participants. Deming regression, limits of agreement (LOA) and typical error as a coefficient of variation (CV) were used to quantify agreement (CVa) and reproducibility (CVr). Deming regression revealed no systematic bias for any of the analytes studied, but for insulin there was evidence of a proportional difference at higher concentrations. Measures of GLP17-36 (CVa=24.0%, LOA ±2.5 pg m/l per h), leptin (CVa=9.0%, LOA ×/÷1.19) and glucagon (CVa=21.0%, LOA, ±31.5 pg m/l per h) revealed good agreement between methodological approaches. Fingertip-capillary glucagon was highly reproducible between days (CVr=8.2%). GLP17-36 and leptin demonstrated modest reproducibility (CVr=22.7 and 25.0% respectively). For insulin, agreement (CVa=36.0%, LOA ×/÷1.79) and reproducibility were poor (CVr=36.0%). Collectively, the data demonstrate that fingertip-capillary blood sampling provides a comparable and reproducible alternative to antecubital-venous blood sampling for the quantification of glucagon, and to a lesser extent for GLP17-36 and leptin. Caution should be exercised when utilising fingertip-capillary blood sampling for insulin quantification, and consequently should not be employed interchangeably with antecubital-venous blood sampling.

[Mass spectrometry of blood low-molecular fraction as a method for unification of therapeutic drug monitoring]

The article describes a new therapeutic drug monitoring (TDM) method based on direct infusion of low-molecular fraction of blood into electrospray ionization source of mass spectrometer. This technique allows performing TDM of almost all drugs used in clinic. In article, the universality and high-throughput of the method, that significantly simplifies its wide application, have been shown. Moreover, the possibility of method application in most cases of drug therapy has been argued as a tool of control of drug doses, rationality of drug therapy, and the quality of the drugs themselves. In conclusion, the prospects for application of the method as primary means of improving the quality and personalization of drug therapy have been discussed.

Comparison of oseltamivir and oseltamivir carboxylate concentrations in venous plasma, venous blood, and capillary blood in healthy volunteers

Oseltamivir and oseltamivir carboxylate concentrations were measured in venous plasma, venous blood, and capillary blood taken simultaneously from 24 healthy volunteers. Median (range) venous-blood-to-plasma ratios were 1.42 (0.920 to 1.97) for oseltamivir and 0.673 (0.564 to 0.814) for oseltamivir carboxylate. Capillary blood/venous plasma ratios were 1.32 (0.737 to 3.16) for oseltamivir and 0.685 (0.502 to 1.34) for oseltamivir carboxylate. Oseltamivir concentrations in venous and capillary blood were similar. Oseltamivir carboxylate showed a time-dependent distribution between venous and capillary blood.

Multiplexed quantitation of endogenous proteins in dried blood spots by multiple reaction monitoring-mass spectrometry

Dried blood spot (DBS) sampling, coupled with multiple reaction monitoring mass spectrometry (MRM-MS), is a well-established approach for quantifying a wide range of small molecule biomarkers and drugs. This sampling procedure is simpler and less-invasive than those required for traditional plasma or serum samples enabling collection by minimally trained personnel. Many analytes are stable in the DBS format without refrigeration, which reduces the cost and logistical challenges of sample collection in remote locations. These advantages make DBS sample collection desirable for advancing personalized medicine through population-wide biomarker screening. Here we expand this technology by demonstrating the first multiplexed method for the quantitation of endogenous proteins in DBS samples. A panel of 60 abundant proteins in human blood was targeted by monitoring proteotypic tryptic peptides and their stable isotope-labeled analogs by MRM. Linear calibration curves were obtained for 40 of the 65 peptide targets demonstrating multiple proteins can be quantitatively extracted from DBS collection cards. The method was also highly reproducible with a coefficient of variation of <15% for all 40 peptides. Overall, this assay quantified 37 proteins spanning a range of more than four orders of magnitude in concentration within a single 25 min LC/MRM-MS analysis. The protein abundances of the 33 proteins quantified in matching DBS and whole blood samples showed an excellent correlation, with a slope of 0.96 and an R(2) value of 0.97. Furthermore, the measured concentrations for 80% of the proteins were stable for at least 10 days when stored at -20 °C, 4 °C and 37 °C. This work represents an important first step in evaluating the integration of DBS sampling with highly-multiplexed MRM for quantitation of endogenous proteins.

Can finger-prick sampling replace venous sampling to determine the pharmacokinetic profile of oral paracetamol?

WHAT IS ALREADY KNOWN ABOUT THE SUBJECT: Finger-prick blood samples are increasingly used for the clinical and biomedical measurement of drugs and endogenous substance concentration. The use of different sampling sites can give rise to different drug concentration measurements.

WHAT THIS STUDY ADDS

During the absorption phase, the paracetamol concentration in finger-prick blood samples is significantly greater than that in venous blood samples, following oral administration. Finger-prick and venous blood samples will result in equivalent pharmacokinetic parameters of oral paracetamol only after distribution equilibrium is attained. The drive to increase the availability of paediatric pharmacokinetic data with minimum blood loss has led to the development of micro-sampling techniques. However studies have suggested that pharmacokinetic data from venous or capillary blood samples may not be directly comparable.

AIM

The aim of this study was to determine whether paracetamol demonstrates concentration differences between finger-prick and venous blood samples.

METHODS

Paired finger-prick and venous blood samples were taken at 0, 15, 30 and 60 min following 1 g oral paracetamol, from 12 male adult subjects. Paracetamol concentration was determined using HPLC and UV detection with a LLOQ of 2200 pg on column. Intra-assay coefficient of variation for paracetamol at the LLOQ was 3%.

RESULTS

At 15, 30, and 60 min post dose the median finger-prick paracetamol concentration was 349%, 72%, and 9.3% greater than the equivalent venous concentrations, respectively. Regression analysis confirmed a significant relationship between finger-prick and venous paracetamol concentrations at 15 min (r(2) = 0.81, P = 0.006), at 30 min (r(2) = 0.82, P < 0.0001) and at 60 min (r(2) = 0.87, P < 0.0001) post dose. The regression equation for venous and finger-prick blood concentrations at 15, 30 and 60 min post dose were Venous(15) = Finger(15) - 3.4, Venous(30) = Finger(30) - 3.4 and Venous(60) = 0.68 Finger(60) + 3.06, respectively.

CONCLUSIONS

Paracetamol demonstrates an arteriovenous difference in concentration, and the use of finger-prick samples may give rise to results which differ from those obtained with traditional venous sampling especially during the first 1 h following drug ingestion.

Use of DBS sample collection to determine circulating drug concentrations in clinical trials: practicalities and considerations

Background: A clinical investigation was performed into the practicalities of the collection of blood samples for the determination of drug exposures on filter paper, known as dried blood spot (DBS) sampling using a two-period, single-dose, open-label trial conducted in 11 healthy volunteers who received a single oral dose of paracetamol. Questionnaires relating to the blood sampling and spotting process and tolerability were completed by staff and volunteers. Paracetamol concentrations in DBS samples obtained by venous cannula (DBS-Can) were compared against those from fingerprick (DBS-FP) and fresh whole blood obtained from a cannula (WB-Can). Results: The questionnaires demonstrated that FP and blood spotting was easy to perform and well tolerated and compared favorably with cannula sampling. Paracetamol concentrations in DBS-Can were greater than those in WB-Can (positive bias) except below 8000 ng/ml when both were interchangeable. When comparing DBS-FP to DBS-Can, both the bias and variability differed significantly across the five sampling time points. Conclusion: The study has shown that the DBS technique is practical in the context of a clinical trial. Interchangeability of drug concentrations between blood sampling site and mode of blood collection has to be checked and taken into account when designing pharmacokinetic studies for other compounds.

Potential of dried blood self-sampling for cyclosporine c(2) monitoring in transplant outpatients

Background. Close therapeutic drug monitoring of Cyclosporine (CsA) in transplant outpatients is a favourable procedure to maintain the long-term blood drug levels within their respective narrow therapeutic ranges. Compared to basal levels (C₀), CsA peak levels (C₂) are more predictive for transplant rejection. However, the application of C₂ levels is hampered by the precise time of blood sampling and the need of qualified personnel. Therefore, we evaluated a new C₂ self-obtained blood sampling in transplant outpatients using dried capillary and venous blood samples and compared the CsA levels, stability, and clinical practicability of the different procedures. Methods. 55 solid organ transplant recipients were instructed to use single-handed sampling of each 50 μL capillary blood and dried blood spots by finger prick using standard finger prick devices. We used standardized EDTA-coated capillary blood collection systems and standardized filter paper WS 903. CsA was determined by LC-MS/MS. The patients and technicians also answered a questionnaire on the procedure and sample quality. Results. The C₀ and C₂ levels from capillary blood collection systems (C₀ [ng/mL]: 114.5 ± 44.5; C₂: 578.2 ± 222.2) and capillary dried blood (C₀ [ng/mL]: 175.4 ± 137.7; C₂: 743.1 ± 368.1) significantly (P < .01) correlated with the drug levels of the venous blood samples (C₀ [ng/mL]: 97.8 ± 37.4; C₂: 511.2 ± 201.5). The correlation at C₀ was ρ_cap.-ven. = 0.749, and ρ_{dried blood-ven} = 0.432; at C₂: ρ_cap.-ven. = 0.861 and ρ_{dried blood-ven} = 0.711. The patients preferred the dried blood sampling because of the more simple and less painful procedure. Additionally, the sample quality of self-obtained dried blood spots for LC-MS/MS analytics was superior to the respective capillary blood samples. Conclusions. C₂ self-obtained dried blood sampling can easily be performed by transplant outpatients and is therefore suitable and cost-effective for close therapeutic drug monitoring.

Correlation between finger-prick and venous ciclosporin levels: association with gingival overgrowth and hypertrichosis

The aims of this study were (1) to ascertain ciclosporin C(2) levels currently being achieved in children with steroid-sensitive nephrotic syndrome (SSNS) and renal transplants (RTs), (2) to determine the feasibility of the use of finger-prick samples for the measurement of ciclosporin levels, and (3) to identify any correlation between hypertrichosis or gingival overgrowth (GO) and level of ciclosporin 2 h post-dose (C(2)). Seventy-two children (39 with SSNS, 33 with RT) participated. Ciclosporin 12 h trough (C(12)) and C(2) levels were measured in venous and finger-prick samples by high-performance liquid chromatography tandem mass spectroscopy. Photographs of the teeth and back were taken for assessment of GO and hypertrichosis. Mean (+/-SD) C(2) levels in the SSNS and RT groups were 512 (+/-181) microg/l and 471 (+/-229) microg/l. There was a highly significant relationship between venous and finger-prick ciclosporin levels (r(2) = 0.96, P < 0.0001). Fourteen children had severe GO. There was a small, though statistically significant, impact of ciclosporin level on GO (C(2) r(2) = 0.12, P = 0.003 and C(12) r(2) = 0.06, P = 0.038) but no correlation with dose (milligrammes per kilogramme per day or milligrammes per square metre per day) or duration. Seventeen children had moderate or severe hypertrichosis, this being more common in children of South Asian ethnicity (P < 0.0001). There was no correlation between ciclosporin exposure or duration and hypertrichosis. Finger-prick blood sampling may serve as a practical alternative to venepuncture in children receiving ciclosporin.

A Comparison of Peripheral and Centrally Collected Cyclosporine A Blood Levels in Pediatric Patients Undergoing Stem Cell Transplant

PURPOSE/OBJECTIVES

To measure differences in cyclosporine A (CSA) trough concentrations from blood collected as a peripheral sample and from a CSA-uncontaminated (naive) lumen of a double-lumen central line.

DESIGN

Prospective, comparative study.

SETTING

Pediatric university teaching hospital in metropolitan Australia.

SAMPLE

71 paired central and peripheral CSA blood samples from a convenience sample of 14 pediatric allogeneic stem cell transplant recipients receiving IV CSA as prophylaxis or treatment for graft-versus-host disease. Ages ranged from 2 months to 14 years, 5 months.

METHODS

Comparing blood samples collected from a peripheral site and a CSA-naive lumen of a double-lumen central line. Data were analyzed using a paired student t test and calculation of the 95% confidence interval of the concentration ratio from different sampling sites.

MAIN RESEARCH VARIABLES

Site of blood sampling and CSA trough concentrations.

FINDINGS

No significant difference existed between CSA concentration in samples collected from the different sites in children receiving intermittent infusions of CSA (p = 0.13). The 95% confidence interval of the CSA concentration ratio was 0.92 1.04.

CONCLUSIONS

When CSA is administered on an intermittent dosing schedule, comparable CSA trough concentrations can be determined from blood collected via the CSA-naive lumen of a double-lumen central line or at a peripheral sampling site.

IMPLICATIONS FOR NURSING

Pediatric allogeneic stem cell transplant recipients who require regular CSA trough concentrations no longer will require peripheral blood samples when receiving an intermittent dosing schedule.

Monitoring of cyclosporine levels in transplant recipients using self-administered fingerprick sampling

Use of C(2) monitoring for cyclosporine A (CsA) microemulsion results in improved clinical outcomes vs. trough (C(0)) monitoring. Logistical issues include accurate timing of the C(2) sample; requirement for sample dilution with most standard assay techniques; and inconvenience for patients. Recently, it has been shown that CsA concentrations in capillary blood correlate closely with levels in venepuncture samples, and that liquid chromatography tandem mass spectrometry (LC-MS/MS) can analyse CsA concentration using undiluted capillary blood from fingerprick samples. In a study to assess the feasibility of CsA monitoring, 52 stable heart transplant patients were provided with kits to take fingerprick trough and C(2) blood samples at home, returning them to the laboratory by post for LC-MS/MS analysis. In total, 225 samples were provided, of which 14 (6%) were unsuitable for analysis because of clotting (n = 10) or insufficient volume (n = 4). Discomfort was not a problem and initial difficulties that some patients reported in taking the samples resolved with experience. All samples were returned by the postal system in a timely manner. Use of fingerprick assays could allow transplant physicians to have access to C(2) levels when patients visit the clinic for review, and avoids the need for patients to attend the clinic or local healthcare centre solely for venepuncture. A barrier to more widespread introduction of fingerprick testing is likely to be lack of suitable MS facilities and trained personnel. In conclusion, self-administered fingerprick testing for CsA blood levels is practical to implement and highly convenient for patients and offers advantages for the transplant team.

Fingerprick blood samples can be used to accurately measure tacrolimus levels by tandem mass spectrometry

Regular monitoring of tacrolimus levels is an essential component of post-transplantation follow up in children receiving this drug. We have developed a high performance liquid chromatography tandem mass spectrometry (HPLC T-MS) methodology which measures whole blood tacrolimus levels using a 10 microL sample, thus allowing the use of fingerprick blood sampling. The aim of this study was to determine the degree of relationship between fingerprick and venous tacrolimus levels measured by HPLC T-MS and venous levels measured using the Abbott IMx tacrolimus II assay (IMx). This has not previously been investigated. Blood samples were collected from children on five separate occasions. In addition to the routine venous IMx sample, a further venous and fingerprick sample were collected for tacrolimus level measurement by HPLC T-MS. These were mailed to the central laboratory. One hundred and seventy-two sets of triplicate samples were collected from 36 children (33 kidney, two kidney-pancreas and one kidney-heart). Linear regression analysis showed highly significant relationships between HPLC T-MS venous and IMx venous levels (r(2) = 0.83), HPLC T-MS fingerprick and HPLC T-MS venous levels (r(2) = 0.85) and HPLC T-MS fingerprick and IMx venous levels (r(2) = 0.71) (all p < 0.0001). Bland Altman analysis showed a small, although statistically significant difference between measured values, fingerprick HPLC T-MS levels being lower than venous IMx levels, the mean difference being 0.58 ng/mL (95% CI 0.26-0.91, t = 3.54, d.f. = 168, p = 0.0005 one sample t-test). Precise conversion between the two techniques could be achieved using the regression formula; IMx venous level = 0.751 + 0.978. HPLC T-MS fingerprick level. There is a strong significant relationship between fingerprick blood tacrolimus levels measured by HPLC T-MS and venous blood levels measured by IMx, allowing the two to be used interchangeably for routine clinical purposes.

Determination of cyclosporine in saliva using liquid chromatography-tandem mass spectrometry

Saliva may offer an alternative specimen for the therapeutic monitoring of cyclosporine (CsA) in children and patients with difficult venous access. For a highly protein-bound drug such as CsA, saliva may also provide a practical approach for measuring the unbound concentration. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is ideally suited for the measurement of drugs in saliva. A solid-phase extraction technique, analytic liquid chromatography over an Aqua Perfect C18 column, maintained at 65 degrees C, and electrospray tandem mass spectrometry were used to quantify CsA in saliva. The method used cyclosporine C (CsC) as the internal standard. Mobile phase comprised of a 97:3 vol/vol mixture of methanol and 30 mmol ammonium acetate at a flow rate of 0.5 mL/min. Chromatograms using mass transitions of m/z 1219.9 --> m/z 1202.9 for CsA and m/z 1235.9 --> m/z 1218.9 for CsC were obtained. The calibration curve was linear from 1 to 300 microg/L with correlation coefficient values ranging from 0.9732 to 0.9968). The lower limit of quantification was 1 microg/L, and limit of detection was 0.6 microg/L with an average extraction recovery of 84.7 +/- 2.6% for CsA and 93.7 +/- 4.4% for CsC from the saliva matrix. The accuracy of the method ranged from 92% to 104.7%, and the intra- and interrun coefficients of variation were 6.9-12.2% and 8.3-12.1%, respectively. The correlation coefficient value between the CsA concentration measurements in 15 paired blood-saliva samples from kidney transplant recipients was 0.695 (P = 0.006). The noninvasive and simple method of saliva collection coupled with the LC-MS/MS quantification technique for CsA analysis would generate novel data that could benefit patients undergoing CsA therapy.

Simultaneous and rapid analysis of cyclosporin A and creatinine in finger prick blood samples using liquid chromatography tandem mass spectrometry and its application in C2 monitoring

A simple and rapid liquid chromatography tandem mass spectrometry (LC-MS/MS) method for the simultaneous analysis of cyclosporin A (CsA) and creatinine using capillary blood has been developed. Venous and capillary blood samples were taken predose and at C2 from 65 heart and lung transplant recipients (65 x 4 samples). For comparisons, serum creatinine and blood CsA concentrations were measured by the Jaffe and EMIT methods, respectively, using an Olympus AU600 analyzer. For the LC-MS/MS assay, samples were prepared in a 96 x 700-microL well block by adding 10 microL of blood (or serum) to 40 microL of 0.1 mol/L zinc sulphate solution containing deuterated creatinine internal standard. Proteins were precipitated by adding 100 microL acetonitrile containing ascomycin internal standard. After vigorous mixing and centrifugation, 5 microL of the supernatant was injected into the LC-MS/MS system. A Waters 2795 high-performance liquid chromatography (HPLC) system was used to elute a C18 cartridge (3 mm x 4 mm) at 0.6 mL/min with a step gradient of 50-100% methanol containing 2 mmol/L ammonium acetate and 0.1% (v/v) formic acid. The column was maintained at 55 degrees C, and the retention times were creatinine, 0.4 minutes; ascomycin, 0.98 minutes; and CsA, 1.2 minutes. Cycle time was 2.5 minutes, injection to injection. The analytes were monitored using a Quattro microtandem mass spectrometer operated in multiple reaction monitoring mode using the following transitions: creatinine, m/z 114>44; d3-creatinine (IS), m/z 117>47; ascomycin (IS), m/z 809>756; and CsA, m/z 1,220>1,203. Assay characteristics were CsA intraassay CV, 3.6-3.0% (33-1,500 microg/L); CsA interassay CV, 6.7-2.5% (10-5,000 microg/L); LC-MS/MS capillary [CsA] = 0.99 x LC-MS/MS venous [CsA] - 4.2, R = 0.98; and LC-MS/MS venous [CsA] = 0.93 x EMIT venous [CsA] + 2.9, R = 0.98. Creatinine intraassay CV, 6.6-2.5% (20-720 micromol/L); interassay CV, 5.7-3.3% (80-590 micromol/L); LC-MS/MS capillary [creatinine] = 0.99 Jaffe plasma [creatinine] -42.6, R = 0.87. Total time for the preparation and analysis of 30 samples was approximately 2 hours. This assay will provide a flexible, robust, and cost-effective solution for the monitoring of CsA and creatinine in transplant recipients with potential applications in pediatric medicine and pharmacokinetic studies, in which frequent sampling is required.

New concepts in cyclosporine monitoring

PURPOSE OF REVIEW

Inadequate cyclosporine exposure is a key risk factor for acute rejection, and may contribute to the development of chronic rejection and graft failure. Pre-dose monitoring does not accurately measure drug exposure because of extensive inter- and intra-patient variability in cyclosporine absorption and metabolism. Limited sampling, using individual timed specimens, offers a new, simple and accurate alternative for clinical monitoring of cyclosporine.

RECENT FINDINGS

The area under the first 4 h of the concentration-time curve (AUC ) and the single-point concentration at 2 h post-dose (C2) are key measures of cyclosporine exposure. De novo studies show that achieving an AUC value of more than 4400 microg.h/l or a C2 level of 1500-2000 microg/l during the first 5 days post-transplant minimizes the risk of rejection and improves graft function. Maintenance studies suggest that reducing the C2 level to approximately 800 microg/l after 3-6 months may improve the serum creatinine level, blood pressure, general well-being and reduce adverse effects.

SUMMARY

Single-point C2 monitoring can be implemented quickly and simply with appropriate site and patient training. The timing of phlebotomy is more critical, but immunoassay bias is lower with 2 h post-dose than with trough level measures. Single-point C2 monitoring may be effective in liver and heart replacement, but initial target levels for liver transplantation are lower because cyclosporine is transported directly to the liver via the portal system. C2 monitoring is now being widely adopted as an accurate and practical measure of drug exposure, and can be combined with pharmacodynamic methods to optimize immunosuppression.

Therapeutic drug monitoring for immunosuppressants

BACKGROUND

Immunosuppressants have significantly increased patient survival, e.g. in renal transplant up to 90% for the first year.

METHODS

Four immunosuppressants are used for clinical applications in the United States: cyclosporine (CsA) (Sandimmune and Neoral), FK 506-tacrolimus (ProGraf), mycophenolic mofetil (CellCept)--the prodrug for the mycophenolic acid (MPA), and rapamycin (RAPA) (Sirolimus). For CsA and FK 506, the rationale for monitoring is due to the variable pharmacokinetics, acute infection, dosage adjustment, non-compliance check, and for long-term maintenance therapy. Targeted whole blood concentrations ranges are: for CsA, 100-400 ng/ml depending on the methods, therapy and organs; and for FK 506, 5-20 ng/ml. For MPA, drug bioavailability--the plasma area-under-curve up to 12 h of 32.2-60.6 mg h/l was correlated to the biopsy-proven rejection rate of <10%. Monitoring is advocated for liver and renal transplants, for pediatrics, and for checking for non-compliance. RAPA monitoring is useful to check for variable pharmacokinetics, for non-compliance and others. The therapeutic range is tentatively targeted for 5-15 ng/ml. Monitoring methodologies are: for CsA, immunoassays such as fluorescence polarization immunoassay, and liquid chromatography (LC); for FK 506, microparticle enzyme immunoassay (MEIA); for MPA, enzyme multiplied immunoassay and LC; and for RAPA, MEIA, LC and LC-mass spectrometry. Proficiency survey programs for CsA and FK 506 are available from the US and Europe.

CONCLUSIONS

Monitoring of immunosuppressants has become an essential adjunct to the drug therapy for organ transplant patients.