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Schellings M.W.M.,Clinical Laboratory | Schellings M.W.M.,Maxima Medical Center | Boonen K.,Clinical Laboratory | Schmitz E.M.H.,Maxima Medical Center | And 10 more authors.
Thrombosis Research | Year: 2016

Major orthopaedic surgery is associated with an increased risk of venous thromboembolism. Direct oral anticoagulants (DOACs) are recommended as thromboprophylactic agents after orthopaedic surgery. Although routine monitoring of DOACs in general is not required, measuring DOAC concentration may be necessary in clinical settings. The effects of DOACs on routine coagulation assays in spiked material are studied extensively, however, few data are available on DOAC concentration in patients after major orthopaedic surgery. We measured trough and peak DOAC concentrations with UPLC-MS/MS and routine coagulation tests in a prospective study including 40 patients receiving thromboprophylactic treatment with dabigatran 220 mg od and 40 patients receiving rivaroxaban 10 mg od after major orthopaedic surgery. For rivaroxaban, the median trough concentration with UPLC-MS/MS was 17.1 ng/mL and median peak concentration was 149 ng/mL. The anti-Xa assay displayed a good correlation, but a positive bias in comparison to the reference method. Furthermore, trough levels were mostly below the LOD of the anti-Xa assay. For dabigatran, the median trough concentration with UPLC-MS/MS was 12.1 ng/mL, and median peak level was 80.8 ng/mL. A positive bias was found when results from coagulation assays were compared to UPLC-MS/MS data. However, the addition of glucuronidated metabolites to dabigatran concentration UPLC-MS/MS data generally resolved most of this bias. Age was found to have a significant influence on dabigatran pharmacokinetics, irrespective of kidney function, whereas no effect of age was found during rivaroxaban treatment. In both treatment groups, female subjects displayed faster pharmacokinetics in comparison to male subjects, although not reaching significance. We conclude that UPLC-MS/MS is the method of choice to measure trough concentrations of DOACs in patients after orthopaedic surgery. Current coagulation assays are not suited for this purpose. We found large heterogeneity in both peak and trough concentrations of DOACs, and showed that pharmacokinetics of novel oral anticoagulants may be influenced by age and gender. Whether patients with high or low trough concentrations are at increased risk for bleeding or thromboembolic events respectively remains to be established. © 2016 Elsevier Ltd. All rights reserved. Source


Schmitz E.M.H.,Expert Center Clinical Chemistry Eindhoven | Schmitz E.M.H.,Maxima Medical Center Veldhoven | Schmitz E.M.H.,Clinical Laboratory | Schmitz E.M.H.,TU Eindhoven | And 15 more authors.
Clinical Chemistry and Laboratory Medicine | Year: 2016

Background: Therapeutic drug monitoring (TDM) of infliximab (IFX, Remicade®) can aid to optimize therapy efficacy. Many assays are available for this purpose. However, a reference standard is lacking. Therefore, we evaluated the analytical performance, agreement and clinically relevant differences of three commercially available IFX ELISA kits on an automated processing system. Methods: The kits of Theradiag (Lisa Tracker Infliximab), Progenika (Promonitor IFX) and apDia (Infliximab ELISA) were implemented on an automated processing system. Imprecision was determined by triplicate measurements of patient samples on five days. Agreement was evaluated by analysis of 30 patient samples and four spiked samples by the selected ELISA kits and the in-house IFX ELISA of Sanquin Diagnostics (Amsterdam, The Netherlands). Therapeutic consequences were evaluated by dividing patients into four treatment groups using cut-off levels of 1, 3 and 7 μg/mL and determining assay concordance. Results: Within-run and between-run imprecision were acceptable (≤12% and ≤17%, respectively) within the quantification range of the selected ELISA kits. The apDia assay had the best precision and agreement to target values. Statistically significant differences were found between all assays except between Sanquin Diagnostics and the Lisa Tracker assay. The Promonitor assay measured the lowest IFX concentrations, the apDia assay the highest. When patients were classified in four treatment categories, 70% concordance was achieved. Conclusions: Although all assays are suitable for TDM, significant differences were observed in both imprecision and agreement. Therapeutic consequences were acceptable when patients were divided in treatment categories, but this could be improved by assay standardization. © 2016 by De Gruyter 2016. Source


Helmich F.,TU Eindhoven | Helmich F.,Expert Center Clinical Chemistry Eindhoven | van Dongen J.L.J.,TU Eindhoven | Kuijper P.H.M.,Expert Center Clinical Chemistry Eindhoven | And 3 more authors.
Clinica Chimica Acta | Year: 2016

Background Given the excellent performance of modern mass spectrometers, their clinical application for the analysis of macromolecules is a growing field of interest. This principle is explored by hemoglobin analysis, which is a representative example by its molecular weight and clinical relevance in e.g. screening programs for thalassemia and hemoglobin variants. Considering its abundance and cellular containment, pre-analysis is significantly reduced allowing for essential rapid acquisitions. Methods By parallel analysis of routine diagnostics for hemoglobin variants and thalassemia, we acquired samples of adults who were consented for hemoglobinopathy screening in our clinical laboratory. The pre-analytical process comprised of red cell lysis only; without further digestion and purification steps, the samples were directly injected in an electrospray ionization quadrupole time-of-flight setup and the intact proteins were analyzed by flow injection analysis. After optimization of process parameters, the deconvoluted mass spectra revealed the presence of α- and β-globulins. The reference ranges for the average mass of both globulins and their intensity ratio (α/β-ratio) were deduced from a disease-free subgroup and patients with a hemoglobinopathy were compared. Results The α/β-ratio is a poor marker for thalassemia patients, yet deviant α/β-ratios are found for patients with a hemoglobin variant. Mass deviations down to 1 Da can be resolved; even if the patient suffers from a heterozygotic disorder, the average mass is found outside the established reference interval. Conclusions Although subjects with mild thalassemia were not detected, all patients with a hemoglobin variant were resolved by top-down mass spectrometry using the average globulin mass and the α/β-ratio as screening parameters. © 2016 Source


Schmitz E.M.H.,Clinical Laboratory | Schmitz E.M.H.,TU Eindhoven | Schmitz E.M.H.,Expert Center Clinical Chemistry Eindhoven | Boonen K.,Clinical Laboratory | And 11 more authors.
Journal of Thrombosis and Haemostasis | Year: 2014

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. © 2014 International Society on Thrombosis and Haemostasis. Source

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