Rivaroxaban: Quantification by anti-FXa assay and influence on coagulation tests A study in 9 Swiss laboratories

INTRODUCTION: Rivaroxaban (RXA) is licensed for prophylaxis of venous thromboembolism after major orthopaedic surgery of the lower limbs. Currently, no test to quantify RXA in plasma has been validated in an inter-laboratory setting. Our study had three aims: to assess i) the feasibility of RXA quantification with a commercial anti-FXa assay, ii) its accuracy and precision in an inter-laboratory setting, and iii) the influence of 10mg of RXA on routine coagulation tests. METHODS: The same chromogenic anti-FXa assay (Hyphen BioMed) was used in all participating laboratories. RXA calibrators and sets of blinded probes (aim ii.) were prepared in vitro by spiking normal plasma. The precise RXA content was assessed by high-pressure liquid chromatography-tandem mass spectrometry. For ex-vivo studies (aim iii), plasma samples from 20 healthy volunteers taken before and 2 - 3hours after ingestion of 10mg of RXA were analyzed by participating laboratories. RESULTS: RXA can be assayed chromogenically. Among the participating laboratories, the mean accuracy and the mean coefficient of variation for precision of RXA quantification were 7.0% and 8.8%, respectively. Mean RXA concentration was 114±43?g/L .RXA significantly altered prothrombin time, activated partial thromboplastin time, factor analysis for intrinsic and extrinsic factors. Determinations of thrombin time, fibrinogen, FXIII and D-Dimer levels were not affected. CONCLUSIONS: RXA plasma levels can be quantified accurately and precisely by a chromogenic anti-FXa assay on different coagulometers in different laboratories. Ingestion of 10mg RXA results in significant alterations of both PT- and aPTT-based coagulation assays.

[Laboratory diagnostic with regard to new anticoagulants - monitoring and influence on coagulation tests]

New oral anticoagulants promise to overcome essential drawbacks of traditional substances. They have a predictable therapeutic effect, a wide therapeutic window, only limited interaction with food and drugs and can be administered p.o. with a fixed dose. On the other hand, knowledge on the laboratory management of new anticoagulants is limited. In the present article we discuss possible indications and available assays for monitoring of Rivaroxaban, Apixaban and Dabigatran. Furthermore, we discuss interpretation of routine coagulation tests during therapy with these new drugs.

[New oral anticoagulants - influence on coagulation tests].

The new oral anticoagulants (NOACs) represent alternative antithrombotic agents for prophylaxis and therapy of thromboembolic diseases. They act either by inhibition of the clotting factor Xa or IIa (thrombin). As a consequence, they influence several coagulation assays (for example prothrombin time, activated partial thromboplastin time). Because of the short half-life of these new agents, these changes show great variations in the course of 24 hours. Furthermore, there are significant differences of laboratory results depending on the used reagents. We explain the influence of apixaban, rivaroxaban (factor Xa inhibitors) and dabigatran (thrombin inhibitor) on the most commonly used coagulation assays. Besides we show that this influence depends on the way of action of the drug as well as on the principle of the coagulation assay. Being aware of this relationships helps to interpret the results of coagulation assays under influence of NOACs correctly.

Improving prehospital trauma management for skiers and snowboarders - need for on-slope triage?

Background Injuries from skiing and snowboarding became a major challenge for emergency care providers in Switzerland. In the alpine setting, early assessment of injury and health status is essential for the initiation of adequate means of care and transport. Nevertheless, validated standardized protocols for on-slope triage are missing. This article can assist in understanding the characteristics of injured winter sportsmen and exigencies for future on-slope triage protocols. Methods Six-year review of trauma cases in a tertiary trauma centre. Consecutive inclusion of all injured skiers and snowboarders aged >15 (total sample) years with predefined, severe injury to the head, spine, chest, pelvis or abdomen (study sample) presenting at or being transferred to the study hospital. Descriptive analysis of age, gender and injury pattern. Results Amongst 729 subjects (total sample) injured from skiing or snowboarding, 401 (55%, 54% of skiers and 58% of snowboarders) suffered from isolated limb injury. Amongst the remaining 328 subjects (study sample), the majority (78%) presented with monotrauma. In the study sample, injury to the head (52%) and spine (43%) was more frequent than injury to the chest (21%), pelvis (8%), and abdomen (5%). The three most frequent injury combinations were head/spine (10% of study sample), head/thorax (9%), and spine/thorax (6%). Fisher's exact test demonstrated an association for injury combinations of head/thorax (p < 0.001), head/abdomen (p = 0.019), and thorax/abdomen (p < 0.001). Conclusion The data presented and the findings from previous investigations indicate the need for development of dedicated on-slope triage protocols. Future research must address the validity and practicality of diagnostic on-slope tests for rapid decision making by both professional and lay first responders. Thus, large-scale and detailed injury surveillance is the future research priority.

Hydrogels for nucleus replacement—Facing the biomechanical challenge

Hydrogels are considered promising for disc regeneration strategies. However, it is currently unknown whether the destruction of the natural interface between nucleus and surrounding structures caused by nucleotomy and an inadequate annulus closure diminishes the mechanical competence of the disc. This in vitro study aimed to clarify these mechanisms and to evaluate whether hydrogels are able to restore the biomechanical behaviour of the disc. Nucleus pressure in an ovine intervertebral disc was measured in vivo during day and night and adapted to an in vitro axial compressive diurnal (15min) and night (30min) load. Effects of different defects on disc height and nucleus pressure were subsequently measured in vitro using 30 ovine motion segments. Following cases were considered: intact; annulus incision repaired by suture and glue; annulus incision with removal and re-implantation of nucleus tissue; and two different hydrogels repaired by suture and glue. The intradiscal pressure in vivo was 0.75MPa during day and 0.5MPa during night corresponding to an in vitro axial compressive force of 130 and 58N, respectively. The compression test showed that neither the implantation of hydrogels nor the re-implantation of the natural nucleus, assumed as being the ideal implant, was able to restore the mechanical functionality of an intact disc. Results indicate the importance of the natural anchorage of the nucleus with its surrounding structures and the relevance of an appropriate annulus closure. Therefore, hydrogels that are able to mimic the mechanical behaviour of the native nucleus may fail in restoring the mechanical behaviour of the disc.

CODE’s new solar radiation pressure model for GNSS orbit determination

The Empirical CODE Orbit Model (ECOM) of the Center for Orbit Determination in Europe (CODE), which was developed in the early 1990s, is widely used in the International GNSS Service (IGS) community. For a rather long time, spurious spectral lines are known to exist in geophysical parameters, in particular in the Earth Rotation Parameters (ERPs) and in the estimated geocenter coordinates, which could recently be attributed to the ECOM. These effects grew creepingly with the increasing influence of the GLONASS system in recent years in the CODE analysis, which is based on a rigorous combination of GPS and GLONASS since May 2003. In a first step we show that the problems associated with the ECOM are to the largest extent caused by the GLONASS, which was reaching full deployment by the end of 2011. GPS-only, GLONASS-only, and combined GPS/GLONASS solutions using the observations in the years 2009–2011 of a global network of 92 combined GPS/GLONASS receivers were analyzed for this purpose. In a second step we review direct solar radiation pressure (SRP) models for GNSS satellites. We demonstrate that only even-order short-period harmonic perturbations acting along the direction Sun-satellite occur for GPS and GLONASS satellites, and only odd-order perturbations acting along the direction perpendicular to both, the vector Sun-satellite and the spacecraft’s solar panel axis. Based on this insight we assess in the third step the performance of four candidate orbit models for the future ECOM. The geocenter coordinates, the ERP differences w. r. t. the IERS 08 C04 series of ERPs, the misclosures for the midnight epochs of the daily orbital arcs, and scale parameters of Helmert transformations for station coordinates serve as quality criteria. The old and updated ECOM are validated in addition with satellite laser ranging (SLR) observations and by comparing the orbits to those of the IGS and other analysis centers. Based on all tests, we present a new extended ECOM which substantially reduces the spurious signals in the geocenter coordinate z (by about a factor of 2–6), reduces the orbit misclosures at the day boundaries by about 10 %, slightly improves the consistency of the estimated ERPs with those of the IERS 08 C04 Earth rotation series, and substantially reduces the systematics in the SLR validation of the GNSS orbits.

The sensitivity and specificity of a diagnostic test of sequence-space synesthesia

People with sequence-space synesthesia (SSS) report stable visuo-spatial forms corresponding to numbers, days, and months (amongst others). This type of synesthesia has intrigued scientists for over 130 years but the lack of an agreed upon tool for assessing it has held back research on this phenomenon. The present study builds on previous tests by measuring the consistency of spatial locations that is known to discriminate controls from synesthetes. We document, for the first time, the sensitivity and specificity of such a test and suggest a diagnostic cut-off point for discriminating between the groups based on the area bounded by different placement attempts with the same item.

The effects of dynamic loading on the intervertebral disc

Loading is important to maintain the balance of matrix turnover in the intervertebral disc (IVD). Daily cyclic diurnal assists in the transport of large soluble factors across the IVD and its surrounding circulation and applies direct and indirect stimulus to disc cells. Acute mechanical injury and accumulated overloading, however, could induce disc degeneration. Recently, there is more information available on how cyclic loading, especially axial compression and hydrostatic pressure, affects IVD cell biology. This review summarises recent studies on the response of the IVD and stem cells to applied cyclic compression and hydrostatic pressure. These studies investigate the possible role of loading in the initiation and progression of disc degeneration as well as quantifying a physiological loading condition for the study of disc degeneration biological therapy. Subsequently, a possible physiological/beneficial loading range is proposed. This physiological/beneficial loading could provide insight into how to design loading regimes in specific system for the testing of various biological therapies such as cell therapy, chemical therapy or tissue engineering constructs to achieve a better final outcome. In addition, the parameter space of 'physiological' loading may also be an important factor for the differentiation of stem cells towards most ideally 'discogenic' cells for tissue engineering purpose.

Erratum to: The effects of dynamic loading on the intervertebral disc

Erratum to: Eur Spine J DOI 10.1007/s00586-011-1827-1 In the original article ‘‘Acknowledgments’’ was missing. The Acknowledgment is given below: Acknowledgments This project was supported by the Swiss National Science Foundation (SNF # 310030-127586/1) and the Department for Orthopedic Research, Insel University Hospital, Bern, Switzerland.

The in vitro effects of dexamethasone, insulin and triiodothyronine on degenerative human intervertebral disc cells under normoxic and hypoxic conditions

Degeneration of intervertebral discs (IVD) is one of the main causes of back pain and tissue engineering has been proposed as a treatment. Tissue engineering requires the use of highly expensive growth factors, which might, in addition, lack regulatory approval for human use. In an effort to find readily available differentiation factors, we tested three molecules – dexamethasone, triiodothyronine (T3) and insulin – on human IVD cells isolated after surgery, expanded in vitro and transferred into alginate beads. Triplicates containing 40 ng/ml dexamethasone, 10 nM T3 and 10 µg/ml insulin, together with a positive control (10 ng/mL transforming growth factor (TGF)-beta 1), were sampled weekly over six weeks and compared to a negative control. Furthermore, we compared the results to cultures with optimized chondrogenic media and under hypoxic condition (2% O2). Glycosaminoglycan (GAG) determination by Alcian Blue assay and histological staining showed dexamethasone to be more effective than T3 and insulin, but less than TGF-beta1. DNA quantification showed that only dexamethasone stimulated cell proliferation. qPCR demonstrated that TGF-beta1 and the optimized chondrogenic groups increased the expression of collagen type II, while aggrecan was stimulated in cultures containing dexamethasone. Hypoxia increased GAG accumulation, collagen type II and aggrecan expression, but had no effect on or even lowered cell number. In conclusion, dexamethasone is a valuable and cost-effective molecule for chondrogenic and viability induction of IVD cells under normoxic and hypoxic conditions, while insulin and T3 did not show significant differences.