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Donor-derived cell-free DNA (dd-cfDNA) is a noninvasive biomarker for comprehensive monitoring of allograft injury and rejection in kidney transplantation (KTx). dd-cfDNA quantification of copies/mL plasma (dd-cfDNA[cp/mL]) was compared to dd-cfDNA fraction (dd-cfDNA[%]) at prespecified visits in 189 patients over 1 year post KTx. In patients (N = 15, n = 22 samples) with biopsy-proven rejection (BPR), median dd-cfDNA(cp/mL) was 3.3-fold and median dd-cfDNA(%) 2.0-fold higher (82 cp/mL; 0.57%, respectively) than medians in Stable Phase patients (N = 83, n = 408) without rejection (25 cp/mL; 0.29%). Results for acute tubular necrosis (ATN) were not significantly different from those with biopsy-proven rejection (BPR). dd-cfDNA identified unnecessary biopsies triggered by a rise in plasma creatinine. Receiver operating characteristic (ROC) analysis showed superior performance (P = .02) of measuring dd-cfDNA(cp/mL) (AUC = 0.83) compared to dd-cfDNA(%) (area under the curve [AUC] = 0.73). Diagnostic odds ratios were 7.31 for dd-cfDNA(cp/mL), and 6.02 for dd-cfDNA(%) at thresholds of 52 cp/mL and 0.43%, respectively. Plasma creatinine showed a low correlation (r = 0.37) with dd-cfDNA(cp/mL). In a patient subset (N = 24) there was a significantly higher rate of patients with elevated dd-cfDNA(cp/mL) with lower tacrolimus levels (<8 μg/L) compared to the group with higher tacrolimus concentrations (P = .0036) suggesting that dd-cfDNA may detect inadequate immunosuppression resulting in subclinical graft damage. Absolute dd-cfDNA(cp/mL) allowed for better discrimination than dd-cfDNA(%) of KTx patients with BPR and is useful to avoid unnecessary biopsies., (© 2019 The Authors. American Journal of Transplantation published by Wiley Periodicals, Inc. on behalf of The American Society of Transplantation and the American Society of Transplant Surgeons.)

Urine screening can be used to detect misuse of illicit drugs and validate opioid replacement therapy compliance. It is common that immunochemical assays are combined with GC-MS for these applications. Bruker has recently released an ion trap mass spectrometer, called Toxtyper™, with the potential to replace current screening algorithms to detect drug misuse. Here, we compare our current strategy of urine screening for misuse of cannabis, amphetamines, cocaine, opiates, benzodiazepine, methadone, sufentanil, and pregabalin to the Toxtyper protocols provided by the manufacturer. The analytical performance of the instrument was determined on a selected drug panel and with 188 urine samples being compared to establish concordance between our currently established approach and the Toxtyper. The lower limits of detection and identification for acetylcodeine, amphetamine, benzoylecgonine, methadone, and nordiazepam were below the common cut-offs for immunological screening assays and comparable to GC-MS. Imprecision and accuracy, both within- and between-series, were consistently <25%. Toxtyper screening for pregabalin and sufentail was less sensitive than a targeted LC-MS/MS assay. Concordance met the predefined criterion of >90% for all drugs, except for pregabalin. Cannabis misuse could not be detected due to the limited sensitivity of the Toxtyper assay protocols used and the inherent imprecision of the assay. Our study has revealed that a considerable portion of our current time-consuming protocol for screening drugs of abuse in urine, based on the combination of multiple analytical methods, could be consolidated by the Toxtyper for a majority of the most-relevant substances in our patient population., (© 2017 The Association for Mass Spectrometry: Applications to the Clinical Lab (MSACL). Published by Elsevier B.V.)

The individualization of immunosuppression is an approach for preventing rejection in the early phase after transplantation and for avoiding the long-term side effects of over immunosuppression. Pharmacodynamic markers, either specific or nonspecific, have been proposed as complementary tools to drug monitoring of immunosuppressive drugs. A key event in graft rejection is the activation and proliferation of the recipient's lymphocytes, particularly T cells. Activated T cells express surface receptors, such as CD25 (the IL-2 receptor) and CD71 (the transferrin receptor), or co-stimulatory molecules (CD26, CD27, CD28, CD30, CD154 or CD40L, and CD134). Both surface marker expression and cell proliferation are predominately assessed by flow cytometry. Protocols have been established and utilized for both in vitro and ex vivo investigations with either isolated lymphocytes or whole blood. This article reviews the current body of research regarding the use of lymphocyte proliferation and surface activation markers with an emphasis on T cells. Experimental and clinical results related to these markers, as well as methodological issues and open questions, are addressed., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Background: In this prospective study we investigated the impact of the proton pump inhibitor (PPI) pantoprazole on the bioavailability of mycophenolic acid (MPA) after oral administration of enteric-coated mycophenolate sodium (EC-MPS; Myfortic) in heart or lung transplant recipients. Previously we demonstrated that pantoprazole reduces the MPA exposure of mycophenolate mofetil (MMF; CellCept) by 34% in area under the concentration-time curve (AUC). Because gastrointestinal side-effects are common after organ transplantation, we investigated the effect of PPI on MPA levels in patients receiving EC-MPS., Methods: MPA plasma concentrations and inosine monophosphate dehydrogenase (IMPDH) activity at baseline, 30 minutes and 1, 2, 3 and 4 hours were obtained from 21 patients. These patients were treated with pantoprazole 40 mg once daily and EC-MPS twice daily at a mean dose of 960 mg. Measurements were repeated after pantoprazole withdrawal., Results: MPA concentrations and IMPDH activities did not reveal any significant difference during PPI treatment and after withdrawal. MPA AUC, MPA C(max) (maximal MPA concentration), the time until C(max) was reached (T(max)) and IMPDH activity AUC all showed no significant difference., Conclusion: We did not find an influence of pantoprazole on EC-MPS pharmacokinetics such as we did for MMF in our previous investigation. A further prospective, large, cross-over study is planned to support these preliminary results. Given that MPA exposure by AUC correlates with the incidence of acute rejection episodes and transplant vasculopathy, the present findings may have clinical implications., (Copyright © 2011 International Society for Heart and Lung Transplantation. Published by Elsevier Inc. All rights reserved.)

Background: Glucuronidation is a major drug-metabolizing reaction in humans. A pharmacological effect of glucuronide metabolites is frequently neglected and the value of therapeutic drug monitoring has been questioned. However, this may not always be true., Methods: In this review the impact of glucuronidation on therapeutic drug monitoring has been evaluated on the basis of a literature search and experience from the own laboratory., Results: The potential role of monitoring glucuronide metabolite concentrations to optimize therapeutic outcome is addressed on the basis of selected examples of drugs which are metabolized to biologically active/reactive glucuronides. Furthermore indirect effects of glucuronide metabolites on parent drug pharmacokinetics are presented. In addition, factors that may modulate the disposition of these metabolites (e.g. genetic polymorphisms, disease processes, age, and drug-drug interactions) are briefly mentioned and their relevance for the clinical situation is critically discussed., Conclusion: Glucuronide metabolites can have indirect as well as direct pharmacological or toxicological effects. Although convincing evidence to support the introduction of glucuronide monitoring into clinical practice is currently missing, measurement of glucuronide concentrations may be advantageous in specific situations. If the glucuronide metabolite has an indirect effect on the pharmacokinetics of the parent compound, monitoring of the parent drug may be considered. Furthermore pharmacogenetic approaches considering uridine diphosphate (UDP) glucuronosyltransferases polymorphisms may become useful in the future to optimize therapy with drugs subject to glucuronidation.