To cite this article: Schmitz EMH, Boonen K, van den Heuvel DJA, van Dongen JLJ, Schellings MWM, Emmen JMA, van der Graaf F, Brunsveld L, van de Kerkhof D. Determination of dabigatran, rivaroxaban and apixaban by ultra-performance liquid chromatrography -tandem mass spectrometry (UPLC-MS/MS) and coagulation assays for therapy monitoring of novel direct oral anticoagulants. J Thromb Haemost 2014; 12: 1636-46.Abstract. Background: Three novel direct oral anticoagulants (DOACs) have recently been registered by the Food and Drug Administration and European Medicines Agency Commission: dabigatran, rivaroxaban, and apixaban. To quantify DOACs in plasma, various dedicated coagulation assays have been developed. Objective: To develop and validate a reference ultra-performance liquid chromatography -tandem mass spectrometry (UPLC-MS/MS) method and to evaluate the analytical performance of several coagulation assays for quantification of dabigatran, rivaroxaban, and apixaban. Methods: The developed UPLC-MS/MS method was validated by determination of precision, accuracy, specificity, matrix effects, lower limits of detection, carry-over, recovery, stability, and robustness. The following coagulation assays were evaluated for accuracy and precision: laboratory-developed (LD) diluted thrombin time (dTT), Hemoclot dTT, Pefakit PiCT, ECA, Liquid anti-Xa, Biophen Heparin (LRT), and Biophen DiXal anti-Xa. Agreement between the various coagulation assays and UPLC-MS/MS was determined with random samples from patients using dabigatran or rivaroxaban. Results: The UPLC-MS/MS method was shown to be accurate, precise, sensitive, stable, and robust. The dabigatran coagulation assay showing the best precision, accuracy and agreement with the UPLC-MS/MS method was the LD dTT test. For rivaroxaban, the anti-factor Xa assays were superior to the PiCT-Xa assay with regard to precision, accuracy, and agreement with the reference method. For apixaban, the Liquid anti-Xa assay was superior to the PiCT-Xa assay. Conclusions: Statistically significant differences were observed between the various coagulation assays as compared with the UPLC-MS/MS reference method. It is currently unknown whether these differences are clinically relevant. When DOACs are quantified with coagulation assays, comparison with a reference method as part of proficiency testing is therefore pivotal.

Skeletal muscle tissue engineering still does not result in the desired functional properties and texture as preferred for regenerative medicine and meat production applications. Electrical stimulation has been appropriately used as a tool to advance muscle cell maturation in vitro, thereby simulating nerve stimulation, as part of the muscle cell niche in vivo. We first investigated the effects of electrical stimulation protocols in two-dimensional (2D) monolayers of C2C12 and translated these protocols to a three-dimensional (3D) model system, based on a collagen type I/Matrigel(™) hydrogel. More importantly, we addressed the ongoing debate of the translation of results found in cell lines (C2C12) to a primary cell source [muscle progenitor cells (MPCs)] in our 3D system. Striking differences in maturation level were found between the different cell sources. Constructs with MPCs were much more mature than C2C12 constructs, based on developed cross-striations and expression levels of mature myosin heavy chain (MHC) isoforms. Overall, electrical stimulation, when optimally timed, accelerated sarcomere assembly in both 2D and 3D. In addition, MPC constructs were more susceptible to the electrical stimulus, resulting in a shift of MHC expression to slower isoforms.

Plasma glucose levels provide the cornerstone of diabetes evaluation. Unfortunately, glucose levels drop in vitro due to glycolysis. Guidelines provide suitable conditions which minimize glycolysis, such as immediate centrifugation or the use of ice/water slurry storage containers. For obvious practical reasons, most laboratories use blood collection tubes containing glycolysis inhibitors. We describe the effect of a variety of commonly used blood collection tubes on in vitro stability of glucose. Furthermore, we looked at the validity of the assumption that glycolytic activity is minimal when blood is kept in an ice/water slurry. Sodium fluoride alone does not reduce in vitro glycolysis in the first 120 minutes after phlebotomy. Addition of citrate almost completely prevented in vitro glycolysis, but showed a positive bias (0.2 mmol/l) compared to control. This is partly due to a small drop in glucose level in control blood, drawn according to the current guidelines. This drop occurs within 15 minutes, in which glycolysis has been described to be minimal and acceptable. NaF-EDTA-citrate based test tubes provide the best pre-analytical condition available. Furthermore, glucose levels are not stable in heparinized blood placed in an ice/water slurry. We strongly advise the use of NaF-EDTA-citrate based test tubes in diabetes research.

Engineered muscle tissues can be used for several different purposes, which include the production of tissues for use as a disease model in vitro, e.g. to study pressure ulcers, for regenerative medicine and as a meat alternative 1 . The first reported 3D muscle constructs have been made many years ago and pioneers in the field are Vandenburgh and colleagues 2,3 . Advances made in muscle tissue engineering are not only the result from the vast gain in knowledge of biochemical factors, stem cells and progenitor cells, but are in particular based on insights gained by researchers that physical factors play essential roles in the control of cell behavior and tissue development. State-of-the-art engineered muscle constructs currently consist of cell-populated hydrogel constructs. In our lab these generally consist of murine myoblast progenitor cells, isolated from murine hind limb muscles or a murine myoblast cell line C2C12, mixed with a mixture of collagen/Matrigel and plated between two anchoring points, mimicking the muscle ligaments. Other cells may be considered as well, e.g. alternative cell lines such as L6 rat myoblasts 4

Urine flow cytometry is a reliable screening method to exclude urinary tract infections. With a cutoff value of 60 bacteria/μL urine, negative predictive value is 100 % and the calculated percentage of false negatives is 0 % (95 % confidence interval 0-3.3 %). Using flow cytometry as a screening method could lead to a reduction in cultures and antibiotics.