Ultra-high throughput dual channel liquid chromatography with tandem mass spectrometry for quantification of four immunosuppressants in whole blood for therapeutic drug monitoring

Liquid chromatography with tandem mass spectrometry (LC-MS/MS) is the golden standard for immunosuppressants analyses, where optimising throughput by parallel chromatography can reduce costs and turnaround time. We aimed to double our system throughput using a dual LC-MS/MS setup. Therefore, two independent UPLC systems were hyphenated to one triple quadrupole MS, with staggered injections from one autosampler on alternating columns. The method simultaneously measured the analytes tacrolimus, sirolimus, everolimus, and cyclosporin A in whole blood using isotope dilution, with a run time of 1.5 min. Using the dual LC-MS/MS system, net run-to-run time improved from 2.3 to 0.98 min per injection, where throughput increased from 26 to 61 injections per hour. For Performance Qualification, 1101 clinical samples were measured on the dual LC-MS/MS system in addition to the standard system, during a period of one month, and the results were compared using Passing Bablok regression and Bland Altman analysis. There was excellent agreement for all four analytes, with regression slopes of 0.98-1.02x and intercepts of -0.11-0.88 µg/L. Minor bias was demonstrated between the systems with mean differences from -0.93 to 1.43%. In conclusion, the throughput was doubled and idle MS time was reduced with good agreement to the standard system. Currently, the method is applied for clinical routine with frequent peak intensities of &gt;180 injections per day.</p

Determination of Ganciclovir and Acyclovir in Human Serum using Liquid Chromatography-Tandem Mass Spectrometry

Abstract OBJECTIVES: Currently there is no data about a liquid chromatography tandem mass spectrometry (LC-MS/MS) assay including ganciclovir and acyclovir using stable-isotopically labeled internal standards. METHODS: LC-MS/MS assay for measurement of ganciclovir and acyclovir using deuterated standards: ganciclovir-[2H5] and acyclovir-[2H4] was developed. The selectivity and sensitivity, linearity, accuracy and precision, recovery, matrix effect, stability, total process efficiency, carry-over and dilution integrity were validated based on EMA and FDA guidelines. RESULTS: The retention time for ganciclovir was 1.1 min and for acyclovir 1.35 min. Calibration curves were linear over a range of 0.1 to 20 mg/L and the correlation coefficient (R2) was 0.99912 for ganciclovir and 0.99945 for acyclovir. The calculated accuracy was –2.0% to 3.1% for ganciclovir and –1.0% to 6.4% for acyclovir. Within-day precision ranged from 1.8% to 6.6% for ganciclovir and 1.6 % to 6.5% for acyclovir and between-day precision 0% to 9.6% for ganciclovir and 0% to 7.9% for acyclovir. CONCLUSIONS: A rapid and validated LC-MS/MS method was developed for measurement of ganciclovir and acyclovir in human serum which can be used in routine patient care and clinical research

Validation of an LC-MS/MS assay for rapid and simultaneous quantification of 21 kinase inhibitors in human plasma and serum for therapeutic drug monitoring

Kinase inhibitors have revolutionized cancer treatment in the past 25 years and currently form the cornerstone of many treatments. Due to the increasing evidence for therapeutic drug monitoring (TDM) of kinase inhibitors, the need is growing for new assays to rapidly evaluate kinase inhibitor plasma concentrations. In this study, we developed an LC-MS/MS assay for the rapid and simultaneous quantification of 21 kinase inhibitors. First, a literature search was conducted to ensure that the linear ranges of the analytes were in line with the reported therapeutic windows and/or TDM reference values. Subsequently, the assay was validated according to FDA and EMA guidelines for linearity, selectivity, carry-over, accuracy, precision, dilution integrity, matrix effect, recovery, and stability. The assay was fast, with a short run-time of 2 min per sample. Sample pre-treatment consisted of protein precipitation with methanol enriched with stable isotope-labeled internal standards (SIL-IS), and the mixture was vortexed and centrifuged before sample injection. Separation was achieved using a C18 column (3 μm,50 × 2.1 mm) with a gradient of two mobile phases (ammonium formate buffer pH 3.5 and acetonitrile). Analyte detection was conducted in positive ionization mode using selected reaction monitoring. The assay was accurate and precise in plasma as well as in serum. Extraction recovery ranged between 95.0% and 106.0%, and the matrix effect was 95.7%-105.2%. The stability of the analytes varied at room temperature and in refrigerated conditions. However, all drugs were found to be stable for 7 days in the autosampler. The clinical applicability of the analytical method (486 analyzed samples between 1 July 2022-1 July 2023) as well as external quality control testing results were evaluated. Taken together, the results demonstrate that the analytical method was validated and applicable for routine analyses in clinical practice.</p

Clinical Validation of the Analysis of Fluconazole in Oral Fluid in Hospitalized Children

Fluconazole is a first-line antifungal agent for the treatment and prophylaxis of invasive candidiasis in pediatric patients. Pediatric patients are at risk of suboptimal drug exposure, due to developmental changes in gastrointestinal and renal function, metabolic capacity, and volume of distribution. Therapeutic drug monitoring (TDM) can therefore be useful to prevent underexposure of fluconazole in children and infants. Children, however, often fear needles and can have difficult vascular access. The purpose of this study was to develop and clinically validate a method of analysis to determine fluconazole in oral fluid in pediatric patients. Twenty-one paired serum and oral fluid samples were obtained from 19 patients and were analyzed using a validated liquid chromatography-tandem mass spectrometry (LC–MS-MS) method after cross-validation between serum and oral fluid. The results were within accepted ranges for accuracy and precision, and samples were stable at room temperature for at least 17 days. A Pearson correlation test for the fluconazole concentrations in serum and oral fluid showed a correlation coefficient of 0.960 (P < 0.01). The mean oral fluid-to-serum concentration ratio was 0.99 (95% confidence interval [CI], 0.88 to 1.10) with Bland-Altman analysis. In conclusion, an oral fluid method of analysis was successfully developed and clinically validated for fluconazole in pediatric patients and can be a noninvasive, painless alternative to perform TDM of fluconazole when blood sampling is not possible or desirable. When patients receive prolonged courses of antifungal treatment and use fluconazole at home, this method of analysis can extend the possibilities of TDM for patients at home

Development of Risk Prediction Equations for Incident Chronic Kidney Disease

IMPORTANCE ‐ Early identification of individuals at elevated risk of developing chronic kidney disease  could improve clinical care through enhanced surveillance and better management of underlying health  conditions.  OBJECTIVE – To develop assessment tools to identify individuals at increased risk of chronic kidney  disease, defined by reduced estimated glomerular filtration rate (eGFR).  DESIGN, SETTING, AND PARTICIPANTS – Individual level data analysis of 34 multinational cohorts from  the CKD Prognosis Consortium including 5,222,711 individuals from 28 countries. Data were collected  from April, 1970 through January, 2017. A two‐stage analysis was performed, with each study first  analyzed individually and summarized overall using a weighted average. Since clinical variables were  often differentially available by diabetes status, models were developed separately within participants  with diabetes and without diabetes. Discrimination and calibration were also tested in 9 external  cohorts (N=2,253,540). EXPOSURE Demographic and clinical factors.  MAIN OUTCOMES AND MEASURES – Incident eGFR <60 ml/min/1.73 m2.  RESULTS – In 4,441,084 participants without diabetes (mean age, 54 years, 38% female), there were  660,856 incident cases of reduced eGFR during a mean follow‐up of 4.2 years. In 781,627 participants  with diabetes (mean age, 62 years, 13% female), there were 313,646 incident cases during a mean follow‐up of 3.9 years. Equations for the 5‐year risk of reduced eGFR included age, sex, ethnicity, eGFR, history of cardiovascular disease, ever smoker, hypertension, BMI, and albuminuria. For participants  with diabetes, the models also included diabetes medications, hemoglobin A1c, and the interaction  between the two. The risk equations had a median C statistic for the 5‐year predicted probability of  0.845 (25th – 75th percentile, 0.789‐0.890) in the cohorts without diabetes and 0.801 (25th – 75th percentile, 0.750‐0.819) in the cohorts with diabetes. Calibration analysis showed that 9 out of 13 (69%) study populations had a slope of observed to predicted risk between 0.80 and 1.25. Discrimination was  similar in 18 study populations in 9 external validation cohorts; calibration showed that 16 out of 18 (89%) had a slope of observed to predicted risk between 0.80 and 1.25. CONCLUSIONS AND RELEVANCE – Equations for predicting risk of incident chronic kidney disease developed in over 5 million people from 34 multinational cohorts demonstrated high discrimination and  variable calibration in diverse populations

Determination of Flucytosine in Human Serum using Liquid Chromatography-Tandem Mass Spectrometry

OBJECTIVES: Flucytosine is an important drug for the combination treatment of cryptococcal meningitis in patients suffering from an infection with human immunodeficiency virus. As new synergistic regimens are being explored in clinical trials a full oral regimen may be near. For such a study evaluation of drug exposure is of critical importance as bioavailability could be compromised and elimination highly depends on renal function. No simple LC-MS/MS method for therapeutic drug monitoring of flucytosine has been published. METHODS: Therefore, a new method using a triple quadrupole mass spectrometer was developed for analysis of flucytosine in human serum, using stable isotopically labeled flucytosine (2H15N-flucytosine) as internal standard. RESULTS: The calibration curve was linear over a range of 2.00 (LLOQ) to 100.0 mg/L with a correlation coefficient of 0.9993. The calculated accuracy ranged from -11.1 % to -1.4 %. Within-run precision ranged from 1.6 % to 4.3 % and between-run precision ranged from 0.0 % to 5.4 %. Evaluation of serum concentrations during routine TDM showed a large variability in serum concentrations. CONCLUSIONS: We conclude that a simple LC-MS/MS method to quantify flucytosine in human serum has successfully been validated and this assay can be used for routine therapeutic drug monitoring as well as clinical studies

Determination of levofloxacin in human serum using liquid chromatography tandem mass spectrometry

A rapid liquid chromatography tandem-mass spectrometry method was developed for the determination of levofloxacin and its metabolite (desmethyl-levofloxacin) in human serum. Sample preparation was done using protein precipitation technique. Our method had a run time of 2.5 min and retention times of 1.6 min for all analytes. The standard curves were linear within the concentration range of 0.10 to 5.00 mg/L for levofloxacin and 0.10 to 4.99 mg/L for desmethyl- levofloxacin; a correlation coefficient (R2) of 0.999 and 0.998 respectively. The lower limit of quantification for both analytes was 0.10 mg/L. Within-day precision ranged from 1.4% and 2.4% for levofloxacin, 1.5% to 5% for desmethyl-levofloxacin and between-day precision ranged from 3.6% to 4.1% for levofloxacin and 0.0% to 3.3% for desmethyl-levofloxacin; whereas, accuracy ranged from 0.1% to 12.7% for levofloxacin and 0.2% to 15.6% for desmethyl-levofloxacin. This method could be a useful asset for routine therapeutic drug monitoring of levofloxacin in multi-drug resistant tuberculosis patients

Development and Validation of a Bioanalytical Method for the Simul- taneous Determination of 14 Antiretroviral Drugs using Liquid Chro- matography-Tandem Mass Spectrometry

OBJECTIVES: The aim was to develop and validate a LC-MS/MS assay to determine antiretrovirals in human plasma for routine therapeutic drug mon-itoring. METHODS: The selectivity, sensitivity, linearity, accuracy, precision, recovery, matrix effect, stability and dilution integrity and carry-over were validated ac-cording to EMA and FDA standards. RESULTS: For accuracy and precision, the highest overall bias was 11.3% at LLOQ of both lopinavir and saquinavir. The highest overall CV was 15.6% at the LLOQ of darunavir. Storage stability at 4°C, 20–25°C and 10°C had a maximum CV of 13.2% at low QC level (0.2 mg/L) for saquinavir. Freeze-thaw stability had a maximum overall bias of 7.4% at low QC level (0.8 mg/L) for tipranavir. Selectivity and specificity showed no interfering peaks of more than 20% of the LLOQ. CONCLUSIONS: The bioanalytical method is suitable for both TDM in stan-dard care and clinical studies. Werf T, Touw D, Alffenaar JW. Develop-ment and validation of a bioanalytical method for the simultaneous determi-nation of 14 antiretroviral drugs using liquid chromatography-tandem mass spectrometry. J Appl Bioanal 4(2), 37-50 (2018)

Determination of Ganciclovir and Acyclovir in Human Serum using Liquid Chromatography-Tandem Mass Spectrometry

OBJECTIVES: Currently there is no data about a liquid chromatography tandem mass spectrometry (LC-MS/MS) assay including ganciclovir and acyclovir using stable-isotopically labeled internal standards. METHODS: A LC-MS/MS assay for measurement of ganciclovir and acyclovir using deuterated standards: ganciclovir-[2H5] and acyclovir-[2H4] was developed. The selectivity and sensitivity, linearity, accuracy and precision, recovery, matrix effect, stability, total process efficiency, carry-over and dilution integrity were validated based on EMA and FDA guidelines. RESULTS: The retention time for ganciclovir was 1.1 min and for acyclovir 1.35 min. Calibration curves were linear over a range of 0.1 to 20 mg/L and the correlation coefficient (R2) was 0.99912 for ganciclovir and 0.99945 for acyclovir. The calculated accuracy was –2.0% to 3.1% for ganciclovir and –1.0% to 6.4% for acyclovir. Within-day precision ranged from 1.8% to 6.6% for ganciclovir and 1.6 % to 6.5% for acyclovir and between-day precision 0% to 9.6% for ganciclovir and 0% to 7.9% for acyclovir. CONCLUSIONS: A rapid and validated LC-MS/MS method was developed for measurement of ganciclovir and acyclovir in human serum which can be used in routine patient care and clinical research

A volumetric absorptive microsampling LC-MS/MS method for five immunosuppressants and their hematocrit effects

AIM: The aim of this study was to develop and validate a LC-MS/MS assay for tacrolimus, sirolimus, everolimus, cyclosporin A and mycophenolic acid using volumetric absorptive microsampling tips as a sampling device and to investigate the effect on the recoveries of the analyte concentration in combination with the hematocrit (HT), which included temsirolimus (a structural analog). RESULTS: The maximum observed overall bias was 9.6% for the sirolimus LLOQ, while the maximum overall coefficient of variation was 8.3% for the everolimus LLOQ. All five immunosuppressants demonstrated to be stable in the volumetic absorbtive microsampling tips for at least 14 days at 25°C. Biases caused by HT effects were within 15% for all immunosuppressants between HT levels of 0.20 and 0.60 l/l, except for cyclosporin A, which was valid between 0.27 and 0.60 l/l. Reduced recoveries were observed at high analyte concentrations in combination with low HT values for sirolimus, everolimus and temsirolimus. CONCLUSION: A robust extraction and analysis method in volumetric absorptive microsampling tips was developed and fully validated. HT- and concentration-related recovery effects were observed but were within requirements of the purpose of the analytical method