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The assessment of the anticoagulant effect of direct oral anticoagulants (DOACs) can be important for rapid medical decision-making, especially in patients needing immediate management. An assay that screens for the absence or presence of a DOAC would help accelerate treatment in these situations. Chromogenic and coagulation methods have several limitations, including limited accuracy, long turnaround time, and their need of specialized laboratories. Oral factor Xa and thrombin inhibitors are also eliminated by the kidneys and can be detected in patient urine samples using a single, rapid, sensitive, and patient-specific qualitative assay. In these tests, the presence or absence of a DOAC in urine can be identified by visually observing specific colors after a few minutes. Several studies have demonstrated the robustness and repeatability of these assays. The specific colors of the test strip also detect creatinine in the urine, which shows whether DOAC excretion is reduced, thus suggesting renal impairment. Persons with amblyopia may use a specific reader. Current indications for using the DOAC Dipstick test include emergency medical situations with severe bleeding and thrombotic events or before urgent major surgical interventions to accelerate medical decision-making., Competing Interests: J.H.: Managing Director of DOASENSE, consulting honoraria Portola, Sanofi Aventis.The other authors do not have any conflicts of interest to declare., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

Background: The utility of measuring non-vitamin K antagonist oral anticoagulants (NOACs) in plasma, serum and urine samples and with the point-of-care test (POCT) on urine samples should be analysed in an international laboratory study., Methods: The study was performed to determine the inter-laboratory variance of data from two chromogenic assays each for the NOACs rivaroxaban, apixaban and dabigatran, and to analyse the sensitivity and specificity of the POCT assays for factor Xa- and thrombin inhibitors. Plasma, serum and urine samples were taken from six patients in each group on treatment with a NOAC., Results: The inter-laboratory variances, which can be identified best by the coefficient of variation, ranged from 46% to 59% for apixaban, 63% to 73% for rivaroxaban and 39% to 104% for dabigatran using plasma, serum or urine samples and two chromogenic assays for each NOAC. The concentrations were about 20% higher in serum compared to plasma samples for apixaban and rivaroxaban, and 60% lower for dabigatran. The concentration in urine samples was five-fold (apixaban), 15-fold (rivaroxaban) and 50-fold (dabigatran) higher. Sensitivity and specificity of POCT for apixaban, rivaroxaban, and dabigatran were all >94%., Conclusions: The inter-laboratory study showed the feasibility of measurement of apixaban, rivaroxaban, and dabigatran in plasma, serum and urine samples of patients on treatment. Dabigatran was determined at far lower levels in serum compared to plasma samples. Concentrations of NOACs in urine were much higher compared to plasma. The POCT was highly sensitive and specific for all three NOACs.

Background: Non-vitamin K antagonist oral anticoagulants (NOACs) are approved for several indications for prophylaxis of thromboembolism at fixed oral doses. The analysis of NOAC activity/concentration may be required in special patient populations. Heptest coagulation assay determines both factor Xa and thrombin inhibitors. The objective of investigations is to analyze the effects of both groups of NOACs on this assay., Methods: The performance of a modified Heptest-STAT clotting assay was compared with specific chromogenic substrate assays for factor Xa (Coamatic, HemosIL) and thrombin (direct thrombin inhibitor assay and S2238 chromogenic assays) for the determination of rivaroxaban, apixaban, and dabigatran in plasma from patients on treatment., Results: For rivaroxaban (n = 74), the concentrations (mean and SD) of Heptest-STAT versus Coamatic and HemosIL assays were 179.3 ± 85.8 ng/mL versus 199.3 ± 105.7 ng/mL and 212.4 ± 115.9 ng/mL (P < 0.0001), and for apixaban (n = 26) 232.8 ± 10.0 ng/mL versus 178.4 ± 64.4 ng/mL (P < 0.0001) and 182.1 ± 73.1 ng/mL (P = 0.0002). For dabigatran (n = 74), the values of Heptest-STAT were 92.3 ± 65.0 ng/mL versus 124.3 ± 85.6 ng/mL (direct thrombin inhibitor assay, P < 0.0001) and 107.5 ± 59.7 ng/mL (S2238 assay, P = 0.0015), respectively. The values of the intraclass coefficient of correlation ranged from 0.64 to 0.91 (Bland-Altman analysis)., Conclusions: The objective of the study was achieved by demonstrating a high correlation of the Heptest-STAT coagulation assay with chromogenic assays for factor Xa inhibiting NOACs and acceptably good correlation with thrombin inhibiting NOACs in plasma samples of patients on treatment.

Patients with indication for anticoagulation may prefer treatment with a vitamin K antagonist (VKA) or non-vitamin K antagonist oral anticoagulant (NOAC). A questionnaire may help to identify the preference of patients for one of the two types of oral anticoagulants and to develop a score for the recommendation to continue or to change the anticoagulant. A score was developed using a questionnaire containing biographic data and eight statements on attitudes on anticoagulation and was derived to trigger continuation or change the type of anticoagulant by defining ranges of terms and weighting of the significant statements identified by logistic regression analysis. Participating patients received either anticoagulation with VKA (group 1, n = 690), were transferred from VKA to NOAC (group 2, n = 158), received NOAC de novo (group 3, n = 137) or were transferred from NOAC to VKA (group 4, n = 19). Four statements were significantly (p values between 0.0347 and < 0.0001) associated with recommendations to maintain or to change the type of anticoagulant for patients in groups 1, 2, or 3 with predictive values of c = 0.83 between groups 1 and 2 and c = 0.71 between groups 1 and 3. From the total number of replies to the statements a score of three grades and two strengths (A = strong, B = moderate) was derived for the recommendations. This tool supports recommendations as to continue or to change the presently used type of oral anticoagulant based on the identification of patients' preferences., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

Background: Oral anticoagulant therapy is currently performed using vitamin K-dependent (VKA) or novel, non-vitamin-K-dependent (NOAC) anticoagulants. Patients can thus be involved into the decision process which type of anticoagulants to use. Preference of patients for a specific type of anticoagulants is included in several international guidelines for prophylaxis of embolic events in patients with atrial fibrillation., Method: Description of the development of a short questionnaire to identify this preference in patients treated with VKA., Results: Using the questionnaires Freiburger personality inventory (FPI-R), health survey SF-12, State-Trait Anxiety Inventory (STAI) and a self-developed questionnaire on anticoagulant therapy, multiple regression analysis identified 7 items for the willingness of patients to change anticoagulation from VKA to NOAC with a probability of about 90%., Conclusion: Further investigations have to be performed to identify the preference of patients for anticoagulation with VKA using this short questionnaire.

Dabigatran, rivaroxaban, and apixaban are direct oral anticoagulants (DOAC) inhibiting thrombin or factor Xa and effectively preventing thromboembolic complications using fixed doses without need for laboratory-guided dose adjustment. Plasma samples are needed to determine the actual concentration or activity of DOACs, which may be required for special patient populations such as those with acute deterioration of renal function due to any disease, before surgical interventions, during bleeding or thrombotic episodes while on therapy with DOACs, the elderly and youngest populations, unexpected pregnancy, suspicion of overdose and toxication, and to control adherence to therapy. Serum samples have several advantages over plasma samples such as no need of sampling with a specific coagulation tube, reduced pre-analytical errors, and longer storage stability. Determination of rivaroxaban and apixaban from serum samples of patients on treatment performed well and better than samples of patients treated with dabigatran compared with plasma samples. Specific adaption to automated coagulation platforms may improve the performance of the assays from serum samples., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

Direct oral anticoagulants (DOACs) were developed for the treatment of thromboembolic diseases to overcome limitations of vitamin K antagonists (VKA). International guidelines on atrial fibrillation acknowledge patients' for antiembolic therapy with VKA or DOAC as relevant decision criteria. The objective assessment of patients' preference social interactions and psychological factors are hard to measure albeit representing important contributors. After a series of structured interviews and pilot studies assessing the preparedness to use DOAC as an anticoagulant and the motivation of patients to participate in clinical studies with DOAC, seven items were identified from several questionnaires by regression analysis. Those items were seen the best to describe the willingness to change anticoagulation from VKA to DOAC. By their use, we aim to develop a tool for the objective identification of the patients' preferences for VKA or for DOAC to increase adherence to therapy and to reduce anticoagulant undertreatment. German-speaking patients were asked to fill out a questionnaire consisting of biographic data and the seven selected items, and 180 patients completed the questionnaire so far. Of these, 90 patients were on treatment with VKA (group 1), 57 patients changed anticoagulation from VKA to DOAC (group 2), 29 patients were DOAC naive patients (group 3), and 4 patients changed from DOAC to VKA (group 4). Overall, 94 patients received VKA, 29 patients received dabigatran, 50 patients received rivaroxaban, and 7 patients received apixaban as an anticoagulant. Eight patients were younger than 40 years, 35 patients were aged between 40 and 59 years, 53 patients were aged between 60 and 70 years, and 84 patients were aged older than 70 years. Indication for anticoagulation were atrial fibrillation (n = 106), pulmonary embolism (n = 24), deep vein thrombosis (n = 40), artificial heart valve replacement (n = 8), or other diseases (n = 2). Based on the results of the analysis, a score will be suggested to identify the preference of patients for anticoagulation with VKA or DOAC. This tool may be useful for practitioners and health-care professionals to support patient adherence to therapy, and thereby increase treatment effectiveness., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

New oral anticoagulant (NOAC) regimens [dabigatran 150 mg (D150) and 220 mg (D220), rivaroxaban 10 mg (R20), and apixaban 2.5 mg bid (A5)] were effective and safe compared to enoxaparin for the prevention of venous thromboembolism (VTE) following elective total knee (TKR) or hip replacement (THR) surgery. First a cluster analysis was used to identify homogeneous studies for the trial programs of each NOAC. Second, only studies reporting VTE and VTE-related death, major bleeding, and mortality were included. The odds ratio (OR) and 95% confidence interval (CI) were calculated for each NOAC regimen versus the comparator. Third, these data were used for the indirect comparison between NOACs. Cluster analysis identified duration of treatment (10 ± 5 and 34 ± 5 days) as the only homogeneous parameter across all NOAC programs (p>0.05) except for A5 and VTE over 10 ± 5 days (analysis not performed). The results of the calculated OR and 95% CI of the four NOAC regimens over 10 ± 5 and 34 ± 5 days showed inferiority of D150 and D220 compared to R10 for VTE (p<0.01, p<0.001). Comparisons of major bleeding and mortality were not different for all indirect comparisons. Despite the lack of standard definitions for VTE and bleeding outcomes, cluster analysis seems to be an appropriate tool to identify homogeneity across trial programs and to perform an indirect comparison for NOACs for prevention of VTE following TKR and THR surgery.

Rivaroxaban and other direct factor Xa inhibitors are used at fixed doses without drug monitoring and dose adjustment. Patients may require determination of the anticoagulant effect during treatment. The aim of this study was to develop a method to reduce the differences between thromboplastin reagents and coagulation analysers for determination of the anticoagulant effect of rivaroxaban in human plasma. Purity of rivaroxaban extracted from commercially available drug was confirmed by mass spectrometry, elemental analysis and 1H-NMR spectroscopy. Coagulation times of pooled human plasma spiked with 50-900  ng/ml rivaroxaban were analysed. Thromboplastin reagents, WHO RBT/90, Innovin, RecombiPlasTin 2G, STA Neoplastin Plus, Technoclot PT Plus and Thromborel S, the manual Kolle-Hook method and the KC10 analyser were used. An international sensitivity index (ISI) was determined for each reagent and coagulation method using the RBT/90 thromboplastin reagent as reference. The orthogonal, used for the determination of the ISI of coumarin plasmas, and ordinary regression analyses were compared. The results showed than increasing concentrations of rivaroxaban prolonged coagulation values of all thromboplastin assays linearly (r (2)= 0.96 and r(2) = 0.99, respectively). The coefficient of variation between the slopes of the dilution curves and the ratios of the thromboplastin reagents were reduced using the international normalized ratio (INR) and ISI calculated for rivaroxaban. The ISIs of the thromboplastin reagents ranged from 0.73 to 1.67 as compared with the WHO reagent using the manual technique. The coefficient of variations between the thromboplastin reagents comparing the orthogonal and the ordinary regression analysis were 6.8 versus 3.7% (Kolle-Hook method, P = 0.0011) and 8.5 versus 4.8% (KC10 method, P < 0.0001). Using ISI for vitamin-K antagonist and rivaroxaban, the INRs for the rivaroxaban-containing samples were significantly different for one of five commercial thromboplastin reagents. In conclusion, the determination of an ISI for rivaroxaban using a WHO thromboplastin reagent is required for commercial thromboplastin reagents. The manual Kolle-Hook method and an ordinary linear regression analysis should be adopted.

Rivaroxaban and other oral direct factor Xa inhibitors (ODiXa) are currently developed for prophylaxis and treatment of thromboembolic diseases using fixed doses. Although routine monitoring is not required, assessing the intensity of anticoagulation may be useful under certain clinical conditions. ODiXa prolong coagulation times of several clotting assays and, thus, their concentration may be determined in factor Xa specific chromogenic substrate assays. So far, no standardized and validated assay is commercially available. Here, five methods (A through E) are studied and optimized to reduce interassay variability. Human pooled plasma was spiked by a serial dilution of rivaroxaban (25-900 ng/ml). The release of para-nitroaniline from the chromogenic substrates was measured by the optical density (OD) at 405 nm. Method B was identified to yield the lowest sum of deviations from the mean value of the OD concentration curve calculated from all assays. Spline functions were developed for OD versus concentration curves for all methods. The calculated OD versus concentration curves overlapped for all methods. The coefficient of variation for all assays and concentrations of rivaroxaban decreased from 25.3 ± 11.4% using the original data to 3.8 ± 2.2% using the calculated data (P < 0.0001). The robustness of the chromogenic assay (method B) remains to be corroborated in interlaboratory comparisons.

Aim: To gather information on anticoagulant effects after the termination of long-term therapy with idraparinux., Methods: The anticoagulant effects of idraparinux, a synthetic polymethylated analogue of its pentasaccharide, were analysed in 23 patients after termination of a 6- or 12-month therapy period for the prevention of recurrent venous thromboembolism (VTE). Plasma samples of patients initially randomized to 2.5 mg idraparinux (normal creatinine clearance) or 1.5 mg idraparinux (creatinine clearance < 30 ml/min) were investigated in the van Gogh trials. At 3-month intervals for up to 15 months following the termination of the therapy, the factor Xa-specific S2222 chromogenic substrate (aXa) assay and Heptest were used to determine various pharmacokinetic parameters and prothrombin-induced clotting time (PiCT), activated partial thromboplastin time (aPTT) and prothrombin time (PT) were determined., Results: Based on the aXa assay and Heptest, the half lives (t1/2) were 60.2 days and 107.7 days (p < 0.0001), maximum drug concentrations (Cmax) were 0.30 and 0.39 microg/l (p = 0.0016), areas under the activity time curve (AUC) were 33.7 and 38.0 microg/l per day (p = 0.0002), plasma clearances were 0.09 and 0.06 ml/min (p < 0.0001), mean residence times (MRT) were 75.4 and 121.9 (p < 0.0001) and volumes of distribution (Vdiss) were 7.4 and 8.61 (p = 0.1336), respectively. After 12 months of treatment (n = 18), the S2222 and Heptest results showed significantly higher Cmax and AUC, lower Vdiss and clearance and unchanged t1/2 and MRT values compared to 6 months of treatment (n = 5). The PiCT was prolonged for a period of 9 months. Coagulation times of aPTT and PT were not influenced. The results of these parameters did not differ between 12 and 6 months of treatment., Conclusion: The data support reports on a non-ionic binding of idraparinux to antithrombin and other proteins. We suggest that these findings may explain some of the findings of the van Gogh Extension trial.

The activated partial thromboplastin time (aPTT) is currently the most common test used to measure the anticoagulation intensity of heparins and direct thrombin inhibitors (DTIs). Vitamin K antagonists variably affect aPTT reagents. Interactions between heparin and DTIs occur during concurrent therapy. Three DTIs (lepirudin, argatroban, melagatran) and one unfractionated heparin (liquemin) were added to normal plasma (NP) samples (n = 23) and to vitamin K antagonist plasma (VKAP) samples (n = 23) of patients treated with phenprocoumon. Lepirudin and argatroban were added at concentrations from 300 to 3000 ng/ml, melagatran from 30 to 1000 ng/ml, and unfractionated heparin from 0.016 to 0.48 IU/ml. Wave parameters of clotting time and aPTT ratio curves were evaluated by multivariate analysis for inhibitors, aPTT reagents and NP and VKAP samples. Normal ranges resulting from NP samples were 34.5 +/- 1.0 s with Pathromtin SL and 33.9 +/- 0.8 s with Platelin LS. Normal ranges using VKAP were 52.8 +/- 2.6 s (Pathromtin SL) and 44.2 +/- 1.1 s (Platelin LS) (P < 0.0001). Variance analysis showed that inhibitors, plasmas (NP versus VKAP) and reagents influenced the wave characteristics of aPTT (s) (P < 0.0001) and aPTT ratios (P < 0.0001). Distinct statistical differences between aPTT reagents on one hand and normal versus vitamin K antagonist plasma on the other hand make a comparison of reported aPTT results difficult, especially during overlapping therapy with vitamin K antagonists.

Purpose: The primary aim was to compare the prevalence of acute and delayed intracranial haemorrhage (ICH) following mild traumatic brain injury (mTBI) in patients on antithrombotic medication referred to a clinic for oral and plastic maxillofacial surgery. The secondary aim was to evaluate the need for short-term hospitalisation based on initial radiological and clinical findings. Methods: This was an observational retrospective single-centre study of all patients on antithrombotic medication who were admitted to our department of oral and plastic maxillofacial surgery with mTBI over a 5 year period. Demographic and anamnesis data, injury characteristics, antithrombotic medication, radiological findings, treatment, and outcome were analysed. Patients were divided into the following four groups based on their antithrombotic medication: (1) single antiplatelet users, (2) vitamin K antagonist users, (3) direct oral anticoagulant users, and (4) double antithrombotic users. All patients underwent an emergency cranial CT (CT0) at admission. Based on clinical and radiological evaluation, different treatment protocols were applied. Patients with positive CT0 findings and patients with secondary neurological deterioration received a control CT (CT1) before discharge. Acute and delayed ICH and patient's outcome during hospitalisation were evaluated using descriptive statistical analysis. Results: A total of 696 patients (mean age, 71.6 years) on antithrombotic medication who presented at our department with mTBI were included in the analysis. Most injuries were caused by a ground-level fall (76.9%). Thirty-six patients (5.1%) developed an acute traumatic ICH, and 47 intracerebral lesions were detected by radiology—most of these in patients taking acetylsalicylic acid. No association was detected between ICH and antithrombotic medication (p = 0.4353). In total, 258 (37.1%) patients were admitted for 48 h in-hospital observation. The prevalence of delayed ICH was 0.1%, and the mortality rate was 0.1%. Multivariable analysis identified a Glasgow Coma Scale (GCS) of < 15, loss of consciousness, amnesia, headache, dizziness, and nausea as clinical characteristics significantly associated with an increased risk of acute ICH, whereas age, sex, and trauma mechanism were not associated with ICH prevalence. Of the 39 patients who underwent a control CT1, most had a decreasing or at least constant intracranial lesion; in three patients, intracranial bleeding increased but was not clinically relevant. Conclusion: According to our experience, antithrombotic therapy does not increase the rate of ICH after mTBI. A GCS of < 15, loss of consciousness, amnesia, headache, dizziness, and nausea are indicators of higher ICH risk. A second CT scan is more effective in patients with secondary neurological deterioration. Initial CT findings were not clinically relevant and should not indicate in-hospital observation. [ABSTRACT FROM AUTHOR]

Identifying adherence to direct oral anticoagulants (DOACs) plays a major role in treatment efficacy and safety. The DOAC Dipstick can detect DOACs in urine samples of acutely diseased patients at plasma thresholds of about 30 ng/mL. A prospective observational consecutive cohort study was performed on outpatients taking DOACs. The presence of direct oral factor Xa inhibitors (DXIs) in patient urine samples were independently evaluated by visual interpretation of the DOAC Dipstick pad colors. DOAC plasma con- centration was assessed using STA®-Liquid Anti-Xa and STA®-Liquid Anti-IIa chromogenic substrate assays. Positive DOAC Dipstick results were compared with a threshold plasma of DOAC concentration ≥30 ng/mL. Of 120 patients (age 55.4 + 16.1 years, female n = 63), 77 were on rivaroxaban and 43 on apixaban. Plasma concentrations were 129 ± 118 ng/mL for rivaroxaban, and 163 ± 130 ng/mL for apixaban, DOAC Dipstick test has a sensitivity of 97.2% and a positive predictive value of 89.5% at 30 ng/mL. No differences occurred between DXIs. Specificity and negative predictive value could not be determined due to the low number of true negative values. There were no differences in the interpretation of rivaroxaban and apixaban pad colors between observers (Kappa 1.0). Results show that DOAC Dipstick may be a useful tool for identifying DXIs in urine samples in an outpatient setting at a plasma threshold ≥ 30 ng/mL. Further studies should include patients treated with dabigatran, vitamin K antagonists, or other anticoagulants. [ABSTRACT FROM AUTHOR]

DOAC Dipstick determines specifically the presence and absence of direct oral anticoagulants (DOACs) from patients' urine samples and handmade test strips performed as well as the commercial version. To compare plasma activity (chromogenic substrate assays) from plasma samples with results from urine samples (DOAC test strips) of patients treated with heparin, low-molecular weight heparin (LMWH) and without anticoagulation. Plasma anti-factor Xa (aXa) activity was determined by Coamatic chromogenic substrate assay and compared to the presence of anticoagulants in urine by DOAC test strips. Patients were treated for least 5 days and samples were taken 4 hrs after administration in comparison to no treatment with an anticoagulant (n = 42). A total of 100 patients were included treated with heparin (n = 29), LMWH nadroparin (n = 29) or no anticoagulants (n = 42). Plasma aXa levels of patients treated with heparin (2 × 7.500 IU daily subcutaneously, 12 male, age 67.4 ± 11.5 years) were 0,18 IU/ml ± 0,15 IU/ml (mean, standard deviation), with LMWH (1 × 3000 IU daily subcutaneously, 15 male, age 64.2 ± 14.1 years) 0,17 IU/ml ± 0,16 IU/l, and with no anticoagulants (28 male, age 64.2 ± 15.6 years) 0,02 IU/ml ± 0.01 IU/ml. All factor Xa and thrombin inhibitor pad results of test strips were negative. We conclude that DOAC Dipstick has a high probability of not detecting heparin and LMWH in patients on treatment as well as in urine samples of patients not treated with an anticoagulant. [ABSTRACT FROM AUTHOR]

Testing for direct oral anticoagulants (DOACs) in patient urine may facilitate medical treatment decisions. The aim of this study was to investigate interobserver variability by 2 independent observers compared to laboratory staff in the visual interpretation of factor Xa (DXI) and thrombin inhibitors (DTI) using the DOAC Dipstick test. We also examined whether test pads reacted to other anticoagulants and abnormal urine colors. The colors of the DOAC Dipstick direct factor Xa inhibitor and thrombin inhibitor pads were interpreted with 100% accuracy (95% confidence interval 0.862 to 1.000) for urine samples from persons treated with apixaban (n = 26), rivaroxaban (n = 24), and dabigatran (n = 29) and without anticoagulant therapy (n = 29). The factor Xa and thrombin inhibitor pads did not interact with heparin, nadroparin, fondaparinux, or coumadin. One µg/mL r-Hirudin and 6 µg/mL argatroban interacted with the DTI pad; however, this is unlikely to cause clinical problems because dabigatran is unlikely to be administered together with r-Hirudin and argatroban in clinical circumstances. Abnormal urine color was reliably detected by the urine color pad, so can prevent false interpretation of the DOAC Dipstick pad colors. In conclusion, we have demonstrated that interobserver variability when interpreting the DOAC Dipstick test strip is low and that factor Xa and thrombin inhibitor pads do not react to other anticoagulants such as heparins and coumadin. R-Hirudin and argatroban can be detected by the thrombin inhibitor pad and abnormal urine colors can be detected by the urine color pad to prevent false interpretation of the results in patient urine samples. [ABSTRACT FROM AUTHOR]

Background: Assessing the anticoagulant effect of dabigatran may be useful in certain clinical settings. When plasma sampling is not available, serum or urine samples may provide another option for dabigatran determinations. Methods: Dabigatran was assessed in patients on treatment under real-life conditions in plasma samples by four clotting time-based assays and in plasma, serum, and urine samples by two chromogenic substrate methods. Results: The concentrations of dabigatran in patients' plasma samples were not different for the Hemoclot test (106.8 ± 89.4 ng/mL) and the ecarin clotting time (ECT, 109.5 ± 74.5 ng/mL, p = 0.58). Activated partial thromboplastin time and prothrombinase-induced clotting time showed low correlations with the other assays. Chromogenic assays measured similar concentrations as Hemoclot and ECT. For both chromogenic assays, the concentrations of dabigatran were about 70% lower in serum than in plasma samples (p < 0.0001). The intra-class coefficient (ICC, Bland-Altman analysis) was strong comparing ECT, Hemoclot thrombin inhibitor (HTI) assay, and the two chromogenic assays (r = 0.889-0.737). The ICC was low for comparisons of the chromogenic assays of serum vs. plasma values (ICC, 0.15 and 0.66). The ICC for the determination of dabigatran in urine samples by the two chromogenic assays (5641.6 ± 4319.7 and 4730.0 ± 3770.2 ng/mL) was 0.737. Conclusions: ECT, HTI, and chromogenic assays can be used to determine dabigatran in plasma samples from patients under real-life conditions. Chromogenic assays require further improvement to reliably measure dabigatran in serum samples. Dabigatran concentrations in urine samples can also be determined quantitatively. [ABSTRACT FROM AUTHOR]

Measurement of the anticoagulant effect of non-vitamin K antagonist oral anticoagulants (NOAC) may be desirable, in particular in patients with acute medical conditions. Useful methods should give results rapidly within minutes, should be easy to perform, specific, and sensitive. Using plasma samples, chromogenic assays can be made to be specific for the two types of NOAC (factor Xa and thrombin inhibitors), and also hemoclot and ecarin clotting time specific for dabigatran. If plasma samples anticoagulated with sodium citrate are not available, blood samples anticoagulated with ethylene diamine tetraacetic acid or serum samples may be regarded as alternatives for the determination of NOAC. At present, dabigatran cannot be determined from serum samples because it may be consumed during the clotting process to obtain serum. NOAC can be determined in urine samples due to their renal elimination. Quantitative methods are preferable to qualitative methods, although the latter may be advantageous in some situations, being developed as point-of-care tests for oral factor Xa and thrombin inhibitors. In these tests, the presence and absence of NOAC in urine can be identified with the naked eye after a few minutes and these tests are highly specific and sensitive. New assays such as a semiquantitative determination in urine samples and measurement using other sample matrices are currently under development. [ABSTRACT FROM AUTHOR]

Background The determination of rivaroxaban and apixaban from serum samples of patients may be beneficial in specific clinical situations when additional blood sampling for plasma and thus the determination of factor Xa activity is not feasible or results are not plausible. Materials and methods The primary aim of this study was to compare the concentrations of rivaroxaban and apixaban in serum with those measured in plasma. Secondary aims were the performance of three different chromogenic methods and concentrations in patients on treatment with rivaroxaban 10 mg od ( n = 124) or 20 mg od ( n = 94) or apixaban 5 mg bid ( n = 52) measured at different time. Results Concentrations of rivaroxaban and apixaban in serum were about 20-25% higher compared with plasma samples with a high correlation ( r = 0·79775-0·94662) using all assays (all P < 0·0001). The intraclass correlation coefficients were about 0·90 for rivaroxaban and 0·55 for apixaban. Mean rivaroxaban concentrations were higher at 2 and 3 h compared with 1 and 12 h after administration measured from plasma and serum samples (all P-values < 0·05) and were not different between 1 vs. 12 h (plasma and serum). Conclusions The results indicate that rivaroxaban and apixaban concentrations can be determined specifically from serum samples. [ABSTRACT FROM AUTHOR]

Rivaroxaban and dabigatran are new oral anticoagulants (NOACs) that inhibit directly factor Xa and thrombin, respectively. These NOACs effectively prevent thromboembolic complications using fixed doses without the need for dose adjustment according to laboratory results. About 60% of rivaroxaban is cleared from circulation by glomerular filtration, 30% of which is excreted as active drug. About 80% of dabigatran is excreted into urine as active compound. Accordingly, both NOACs can be determined in urine by means of chromatographic methods. Only a few laboratories are able to perform such methods, and results are not available within short time frames. New methods have to be developed to obtain results within minutes and possibly as point-of-care (POC) techniques. This testing may be useful for special patient populations such as those with acute deterioration of renal function due to any disease, before surgical interventions, during unexpected bleeding or thrombotic episodes while on therapy with NOACs, the oldest and youngest populations, pregnancy, suspicion of overdose and intoxication, and to determine adherence to therapy. Here we describe results of a POC qualitative assay using urine samples from patients on treatment with dabigatran and rivaroxaban. [ABSTRACT FROM AUTHOR]

New oral anticoagulants (NOAC) are approved for several indications for prophylaxis and treatment of venous thromboembolism and for prevention of embolism in atrial fibrillation at fixed daily doses without need of laboratory guided dose adjustment. Due to their low molecular weight of about 500 to 600 Dalton and their hydrophilicity free anticoagulant is excreted immediately through glomerular filtration into the urine. Impairment of renal function may increase the plasma concentration of the anticoagulants and lowered creatinine clearance is a declared contraindication. In contrast to the initial aim of development the anticoagulant effect is required to be determined in special clinical situations. Several specific and non-specific assays using plasma samples are currently undergoing standardization. As all NOACs are excreted into the urine, specific assays were developed for this matrix to determine them quantitatively of qualitatively. Urine samples can be easily and repetitively obtained avoiding problems and risks associated with blood sampling. The qualitative assay can be performed as a point of care test (POC) also by the patient by judging the different colours for the absence or presence of the drugs with the naked eye. The test is rapid (results available within 15 min), sensitive, specific and accurate and does not require a purified NOAC as control. The tests may be a tool for clinicians who need to know for treatment decisions if a NOAC is on board or not. As the tests are specific for oral direct thrombin inhibitors and for oral direct factor Xa inhibitors, the indication does not interfere with other qualitative POC test in development using clotting systems. The test may be indicated for patients at acute hospitalization, before surgery or central nervous system puncture anaesthesia, if fibrinolytic therapy is indicated, acute deterioration of renal function, and for control of adherence to therapy. [ABSTRACT FROM AUTHOR]

Objective: Recurrent thromboembolic events may occur after termination of anticoagulant therapy for acute venous thromboembolism (VTE) using oral direct thrombin inhibitor ximelagatran. Methods: Patients with VTE recruited at the German study centres were followed-up for an additional 18 months, treated initially with 2⊗36 mg ximelagatran daily or with enoxaparin/warfarin over 6 months (THRIVE Treatment study) and 2⊗24 mg ximelagatran daily or placebo over 18 months (THRIVE III study). Recurrent VTE and the combined outcome events consisting of recurrent VTE, other thrombotic complication, major bleeding and mortality were analysed. Results: In the THRIVE Treatment study, no patient suffered from a recurrent VTE, but 1 patient randomised to enoxaparin/warfarin experienced major bleeding. During follow-up, 4/32 and 3/32 patients initially randomised to ximelagatran and enoxaparin/warfarin developed recurrent VTE (p=0.7024). No major bleed occurred. One patient in each group died. The incidences of the combined outcome events were not different (p=0.9326). In the THRIVE III study, 0/9 versus 5/14 patients randomised to ximelagatran and placebo developed recurrent VTE including 1 fatal pulmonary embolism (p=0.0501). During follow-up, 3/9 and no patients initially randomised to ximelagatran and placebo developed recurrent VTE. One and 3 other outcome events occurred in patients initially randomised to ximelagatran or placebo. During follow-up, recurrent VTE (p=0.6893) and combined outcome events (p=0.3642) were not different between the groups. Conclusion: The results of the follow-up studies suggest that thromboembolic events may re-occur in patients with acute VTE after termination of treatment with both vitamin K-antagonists and ximelagatran. [ABSTRACT FROM AUTHOR]

Introduction: Direct thrombin inhibitors (DTI) prolong the ecarin clotting time (ECT). Oral anticoagulants (OA) decrease prothrombin levels and thus interact with actions of DTIs on the ECT method during concomitant therapy. Materials and methods: Actions of lepirudin, argatroban and melagatran on ECT were investigated in normal plasma (NP) and in plasma of patients (n=23 each) on stable therapy with phenprocoumon (OACP). Individual line characteristics were tested statistically. Results: Control ECT in OACP was prolonged compared to NP (50.1±0.9 vs. 45.7±0.8 s; p<0.001). Lepirudin prolonged the ECT linearly. Argatroban and melagatran delivered biphasic dose–response curves. OA showed additive effects on the ECT of lepirudin but not of argatroban and melagatran. Both in NP and OACP, the first and second slopes of melagatran were steeper compared to argatroban (primary analysis; p<0.001). When using the same drug, slopes in OACP were steeper than in NP (secondary analysis; p<0.001). At similar molar concentrations, the crossing points of both slopes were significantly higher with melagatran (323.1±11.0 s in NP and 333.2±8.2 s in OACP) than with argatroban (219.6±14.7 and 248.4±15.2 s) corresponding to ratios of 7.1±0.2 and 6.7±0.2 (melagatran) vs. 4.8±0.3 and 4.9±03 with argatroban (p<0.0001). Discussion: The patterns of interactions between vitamin K antagonists and DTI effects are different for bivalent (increase of slope without affecting linearity) and monovalent inhibitors (slight increase or alteration of nonlinear slopes), but there are also differences between the two monovalent inhibitors on thrombin inhibition as determined by ECT. [Copyright &y& Elsevier]