Evaluation of the Anti-Factor Xa Chromogenic Assay for Measuring Rivaroxaban Plasma Concentrations Using Calibrators and Controls

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 3330-3330 ◽  
Author(s):  
Meyer Michel Samama ◽  
Genevieve Contant ◽  
Theodore E Spiro ◽  
Elisabeth Perzborn ◽  
Céline Guinet ◽  
...  
Keyword(s):  
Human Plasma ◽  
Calibration Curve ◽  
Plasma Concentrations ◽  
Control Sample ◽  
Factor Xa ◽  
Alternative Methods ◽  
Preliminary Results ◽  
Chromogenic Assay ◽  
Wide Range ◽  
The Mean

Abstract Abstract 3330 Background: Rivaroxaban is an oral, direct Factor Xa inhibitor in an advanced stage of clinical development for the prevention and treatment of thromboembolic disorders. It inhibits Factor Xa activity without requiring cofactors (such as antithrombin) and has been found to have predictable pharmacokinetics and pharmacodynamics in humans. Routine coagulation monitoring is not required, but a quantitative determination of rivaroxaban concentrations might be useful in some cases, such as severe overdose or to measure compliance. Although the prothrombin time assay may be of assistance for the assessment of peak rivaroxaban plasma concentrations using calibrators and controls as previously shown, alternative methods such as the anti-Factor Xa chromogenic assays may allow the measurement of a wider rivaroxaban plasma concentration range. Methods: A multicenter study was initiated to evaluate the suitability of the anti-Factor Xa chromogenic assay for the measurement of rivaroxaban plasma concentrations (ng/mL) using rivaroxaban calibrators and controls, and to assess the inter-laboratory precision of the measurement. A total of 25 centers were provided with sets of rivaroxaban calibrators (0, 41, 209, and 422 ng/mL) and a set of rivaroxaban pooled human plasma controls (20, 199, and 662 ng/mL). The concentrations of the human plasma controls were unknown to the participating laboratories. The evaluation was carried out over 2 consecutive weeks (10 days) by each laboratory using its own anti-Factor Xa reagents as well as 1 provided centrally (modified STA® Rotachrom, Diagnostica Stago, Asnières-sur-Seine, France). A calibration curve was produced each day and the day-to-day precision was evaluated by testing in duplicate 3 human plasma controls. The plasma control sample was diluted (1:3 dilution) and re-tested if the measured level was above the highest concentration of the calibration curve. Results: Preliminary results from 8 centers showed that the mean rivaroxaban concentrations obtained were 21, 199, 549, and 708 ng/mL when using the modified STA Rotachrom method, or 19, 200, 556, and 676 ng/mL when using the local anti-Factor Xa reagents for the human plasma controls (19, 160, and 643 [undiluted and diluted samples] ng/mL, respectively). The mean coefficients of variation were 17.7%, 4.6%, 1.9%, and 8.9%, respectively, when using the modified STA Rotachrom method, or 33.7%, 4.7%, 2.2%, and 7.7%, respectively, when using the local anti-Factor Xa reagents. Conclusions: The preliminary results of this multicenter field trial suggest that the anti-Factor Xa chromogenic method, using rivaroxaban calibrators and controls, is suitable for measuring a wide range of rivaroxaban plasma concentrations. Disclosures: Samama: Bayer Healthcare: Consultancy. Spiro:Bayer Healthcare Pharmaceuticals Inc.: Employment. Perzborn:Bayer Schering Pharma AG: Employment.

Evaluation of the anti-factor Xa chromogenic assay for the measurement of rivaroxaban plasma concentrations using calibrators and controls

2012 ◽  
Vol 107 (02) ◽  
pp. 379-387 ◽  
Author(s):  
Genevieve Contant ◽  
Theodore Spiro ◽  
Elisabeth Perzborn ◽  
Céline Guinet ◽  
Yves Gourmelin ◽  
...  
Keyword(s):  
Human Plasma ◽  
Plasma Concentrations ◽  
Factor Xa ◽  
Factor Xa Inhibitor ◽  
Chromogenic Assay ◽  
Wide Range ◽  
The Mean ◽  
Therapeutic Doses ◽  
Routine Coagulation

SummaryRivaroxaban is an oral, direct factor Xa inhibitor. Routine coagulation monitoring is not required, but a quantitative determination of rivaroxaban concentrations might be useful in some clinical circumstances. This multicentre study assessed the suitability of the anti-factor Xa chromogenic assay for the measurement of rivaroxaban plasma concentrations (ng/ml) using rivaroxaban calibrators and controls, and the inter-laboratory precision of the measurement. Twenty-four centres in Europe and North America were provided with sets of rivaroxaban calibrators (0, 41, 209 and 422 ng/ml) and a set of rivaroxaban pooled human plasma controls (20, 199 and 662 ng/ml; the concentrations were unknown to the participating laboratories). The evaluation was carried out over 10 days by each laboratory using local anti-factor Xa reagents as well as the centrally provided reagent, a modified STA® Rotachrom® assay. A calibration curve was produced each day, and the day-to-day precision was evaluated by testing three human plasma controls. When using the local anti-factor Xa reagents, the mean rivaroxaban concentrations (measured/actual values) were: 17/20, 205/199 and 668/662 ng/ml, and the coefficient of variance (CV) was 37.0%, 13.7% and 14.1%, respectively. When the modified STA Rotachrom method was used, the measured/actual values were: 18/20, 199/199 and 656/662 ng/ml, and the CV was 19.1%, 10.9% and 10.0%, respectively. The results suggest that, by using rivaroxaban calibrators and controls, the anti-factor Xa chromogenic method is suitable for measuring a wide range of rivaroxaban plasma concentrations (20–660 ng/ml), which covers the expected rivaroxaban plasma levels after therapeutic doses.

Prophylactic Disopyramide: Its Clinical Effects Related to Plasma Concentration in Myocardial Infarction

1980 ◽  
Vol 8 (5) ◽  
pp. 314-320 ◽  
Author(s):  
Rowan Mary Hillson ◽  
E Boyd ◽  
J Cunningham
Keyword(s):  
Myocardial Infarction ◽  
Acute Myocardial Infarction ◽  
Plasma Concentration ◽  
Plasma Level ◽  
Plasma Concentrations ◽  
Double Blind Study ◽  
Clinical Effects ◽  
Number Of Patients ◽  
Wide Range ◽  
The Mean

Sixty-three patients, fifty-two with acute myocardial infarction and eleven with ischaemic heart disease or non-cardiac chest pain, were given either disopyramide phosphate or placebo, orally, in a randomized double-blind study. Thirty-two patients on disopyramide (twenty-six with acute myocardial infarction) received an initial dose of 300 mg followed by 150 mg six-hourly for 3 days. There was a reduction in the number of patients with cardiac dysrhythmias on the first 3 days following infarction in subjects taking disopyramide as compared with controls. This reduction was not statistically significant. There was a significant reduction in the mean ectopic count per hour in patients taking disopyramide compared with those taking placebo on the second day only (p < 0.005). Urinary retention, dry mouth and jaundice were recorded more frequently in the test group. There were wide ranges of pre-dose plasma concentrations on all 3 days. (Day 1: 1.3 to 7.7 μg per ml. Day 2: 2.5 to 8.9 μg/ml and Day 3: 2.5 to 11.5 μg per ml). The mean plasma concentration of disopyramide was higher but not significantly so, in the treatment group without evidence of dysrhythmias than those with dysrhythmias (3.8 ± S.D. 1.5 μg/ml and 3.0 ± 0.8 μg/ml respectively). The mean plasma level in patients who required anti-emetic therapy was significantly lower than those who did not (2.8 ± 0.8 μg/ml and 3.8 ± 1.9 μg/ml respectively, p < 0.025). The wide range of plasma levels observed is probably due in part to irregular absorption with vomiting after myocardial infarction. If disopyramide is to be used prophylactically following myocardial infarction, a therapeutic plasma level will be achieved quickly in all cases only by giving an intravenous starting dose.

scholarly journals Determination of edoxaban equivalent concentrations in human plasma by an automated anti-factor Xa chromogenic assay

2017 ◽  
Vol 155 ◽  
pp. 121-127 ◽  
Author(s):  
Ling He ◽  
Jarema Kochan ◽  
Min Lin ◽  
Alexander Vandell ◽  
Karen Brown ◽  
...  
Keyword(s):  
Human Plasma ◽  
Factor Xa ◽  
Chromogenic Assay

Changes in the clearance of total and unbound etoposide in patients with liver dysfunction.

1990 ◽  
Vol 8 (11) ◽  
pp. 1874-1879 ◽  
Author(s):  
C F Stewart ◽  
S G Arbuck ◽  
R A Fleming ◽  
W E Evans
Keyword(s):  
Protein Binding ◽  
Total Bilirubin ◽  
Equilibrium Dialysis ◽  
Plasma Concentrations ◽  
Hepatic Metastases ◽  
T Test ◽  
Systemic Clearance ◽  
Total Clearance ◽  
Wide Range ◽  
The Mean

The disposition of total and non-protein-bound etoposide was investigated in 21 cancer patients receiving etoposide and cisplatin combination chemotherapy. Etoposide plasma concentrations were determined using a specific high-performance liquid chromatography (HPLC) method, and etoposide plasma protein binding was determined by equilibrium dialysis. The patients had a wide range of renal function (creatinine clearance, 32 to 159 mL/min/m2) and hepatic function (total bilirubin range, 0.3 to 21.5 mg/dL; aspartate aminotransferase [AST] range, 14 to 415 IU/L; serum albumin range, 2.7 to 4.1 g/dL). The mean etoposide total systemic clearance was not different in 15 patients with total bilirubin less than 1.0 mg/dL versus six patients with total bilirubin 1.1 to 21.5 mg/dL (18.7 +/- 5.9 mL/min/m2 v 26.4 +/- 10.7 mL/min/m2; t-test P = .06), with a trend toward higher total clearance in the patients with abnormal bilirubin values. However, the mean clearance of unbound etoposide was significantly lower in patients with increased total bilirubin (220 +/- 90 mL/min/m2 v 135 +/- 61 mL/min/m2; t-test P = .027). The fraction of etoposide unbound (fu) in plasma was significantly higher in patients with increased bilirubin (9% +/- 3% v 27% +/- 15%; t-test P = .002), explaining the trend toward higher total clearance in these patients. Etoposide clearance (total or unbound) in the 14 patients with measurable hepatic metastases was not different from the clearance in the seven patients without hepatic metastases. This study provides an explanation for why patients with increased bilirubin do not have lower total systemic clearance of etoposide, and indicates that such patients have a higher exposure to unbound etoposide. The results of ongoing pharmacodynamic studies of total and unbound etoposide in patients with increased bilirubin will determine the clinical relevance of altered etoposide protein binding.

Selectivity Increase Of Chromogenic Assay Of Factor Xa By Use Of Highly Selective Synthetic Thrombin Inhibitor Having Extremely Potent Stereostructure (No. 805)

1981 ◽  
Author(s):  
S Okamoto ◽  
K Ikezawa ◽  
S Nagano ◽  
A Matsuoka ◽  
A Hijikata ◽  
...  
Keyword(s):  
Human Plasma ◽  
Factor Xa ◽  
Assay System ◽  
Thrombin Inhibitor ◽  
Peptide Substrates ◽  
Methyl Methyl ◽  
Chromogenic Assay ◽  
No Inhibition ◽  
Molecular Concentration ◽  
Km Value

Chromogenic peptide substrates S-2222 designed for F. Xa assay is also amidolyzed relatively slowly by thrombin; in the usual F. Xa assay system however a considerable amount of thrombin is inevitably formed. In the present study, therefore, No. 805, highly selective synthetic thrombin inhibitor, (4 methyl- (methyl-tetrahydro-quino- linesulfonyl-arginyl ][ 2-piperidinecarboxylic acid), having extremely potent stereostructure (2R, 4R) at 4-methyl-2- piperidinecarboxylic acid portion, which was reported by S. Okamoto et al. in 1980, was used to improve selectivity of S-2222 for F. Xa assay. F. Xa in human plasma activated by either Russel’s viper venom or thromboplastin was estimated according to the methods by Aurell et al. . Ki of No. 805 for thrombin was found 0.019 juM and presence of No. 805 of 5 mM inhibited thrombin at least by 99.5%. However, No. 805 of this concentration showed no inhibition for purified F. Xa. Results obtained from chromogenic assay for F. Xa by S-2222 with or without No. 805 of 5 mM indicated that 10̴20% of amidolysis was derived from the action of thrombin formed in the assay system. Concerning high Km value of S-2222 to thrombin, molecular concentration of thrombin formed in the assay system was calculated as 3̴6 times of the F. Xa molecular concentration. Use of highly selective and potent synthetic thrombin inhibitor seems to be promissing to improve the selectivity of some other chromogenic assay also.

Radioimmunoassay of corticotropin from plasma.

1982 ◽  
Vol 28 (11) ◽  
pp. 2229-2234 ◽  
Author(s):  
J Gutkowska ◽  
J Julesz ◽  
J St-Louis ◽  
J Genest
Keyword(s):  
Human Plasma ◽  
Glass Powder ◽  
Clinical Investigation ◽  
Plasma Concentrations ◽  
Normal Subjects ◽  
Plasma Samples ◽  
Vycor Glass ◽  
Silica Column ◽  
Highly Sensitive ◽  
The Mean

Abstract We describe a specific and highly sensitive radioimmunoassay for corticotropin (ACTH) in human plasma. As little as 1.9 pg of circulating ACTH can be detected per milliliter (0.44 pmol/L). ACTH is first extracted from plasma samples by adsorption onto pretreated Vycor glass powder, eluted from the adsorbent by acetone, and then lyophilized. For purification of 125I-labeled ACTH, a small octadecasilyl silica column is used. The mean (and SD) concentration of ACTH in plasma from 18 ostensibly normal subjects was 10.3 (4.3) pmol/L. After overnight suppression with dexamethasone in seven of these normal subjects, their ACTH values fell to 2.62 (1.3) pmol/L (p less than 0.0005). This assay will permit clinical evaluation of ACTH plasma concentrations in clinical investigation and of the effects of drug administration on circulating ACTH.

scholarly journals Terrestrial Structure from Motion Photogrammetry for Deriving Forest Inventory Data

2019 ◽  
Vol 11 (8) ◽  
pp. 950 ◽  
Author(s):  
Livia Piermattei ◽  
Wilfried Karel ◽  
Di Wang ◽  
Martin Wieser ◽  
Martin Mokroš ◽  
...  
Keyword(s):  
Structure From Motion ◽  
Forest Inventory ◽  
Point Clouds ◽  
Alternative Methods ◽  
Acquisition Time ◽  
Image Capture ◽  
Wide Range ◽  
Capture Method ◽  
The Mean

The measurements of tree attributes required for forest monitoring and management planning, e.g., National Forest Inventories, are derived by rather time-consuming field measurements on sample plots, using calipers and measurement tapes. Therefore, forest managers and researchers are looking for alternative methods. Currently, terrestrial laser scanning (TLS) is the remote sensing method that provides the most accurate point clouds at the plot-level to derive these attributes from. However, the demand for even more efficient and effective solutions triggers further developments to lower the acquisition time, costs, and the expertise needed to acquire and process 3D point clouds, while maintaining the quality of extracted tree parameters. In this context, photogrammetry is considered a potential solution. Despite a variety of studies, much uncertainty still exists about the quality of photogrammetry-based methods for deriving plot-level forest attributes in natural forests. Therefore, the overall goal of this study is to evaluate the competitiveness of terrestrial photogrammetry based on structure from motion (SfM) and dense image matching for deriving tree positions, diameters at breast height (DBHs), and stem curves of forest plots by means of a consumer grade camera. We define an image capture method and we assess the accuracy of the photogrammetric results on four forest plots located in Austria and Slovakia, two in each country, selected to cover a wide range of conditions such as terrain slope, undergrowth vegetation, and tree density, age, and species. For each forest plot, the reference data of the forest parameters were obtained by conducting field surveys and TLS measurements almost simultaneously with the photogrammetric acquisitions. The TLS data were also used to estimate the accuracy of the photogrammetric ground height, which is a necessary product to derive DBHs and tree heights. For each plot, we automatically derived tree counts, tree positions, DBHs, and part of the stem curve from both TLS and SfM using a software developed at TU Wien (Forest Analysis and Inventory Tool, FAIT), and the results were compared. The images were oriented with errors of a few millimetres only, according to checkpoint residuals. The automatic tree detection rate for the SfM reconstruction ranges between 65% and 98%, where the missing trees have average DBHs of less than 12 cm. For each plot, the mean error of SfM and TLS DBH estimates is −1.13 cm and −0.77 cm with respect to the caliper measurements. The resulting stem curves show that the mean differences between SfM and TLS stem diameters is at maximum −2.45 cm up to 3 m above ground, which increases to almost +4 cm for higher elevations. This study shows that with the adopted image capture method, terrestrial SfM photogrammetry, is an accurate solution to support forest inventory for estimating the number of trees and their location, the DBHs and stem curve up to 3 m above ground.

Plasma Thrombospondin as an Indicator of Intravascular Platelet Activation in Patients with Vasculitis

1987 ◽  
Vol 58 (03) ◽  
pp. 850-852 ◽  
Author(s):  
M B McCrohan ◽  
S W Huang ◽  
J W Sleasman ◽  
P A Klein ◽  
K J Kao
Keyword(s):  
Platelet Activation ◽  
Plasma Levels ◽  
Half Life ◽  
Degradation Products ◽  
Plasma Concentrations ◽  
Primary Source ◽  
Positive Correlation ◽  
Activation Marker ◽  
Fibrin Degradation Products ◽  
The Mean

SummaryThe use of plasma thrombospondin (TSP) concentration was investigated as an indicator of intravascular platelet activation. Patients (n = 20) with diseases that have known vasculitis were included in the study. The range and the mean of plasma TSP concentrations of patients with vasculitis were 117 ng/ml to 6500 ng/ml and 791±1412 ng/ml (mean ± SD); the range and the mean of plasma TSP concentrations of control individuals (n = 33) were 13 ng/ml to 137 ng/ml and 59±29 ng/ml. When plasma TSP concentrations were correlated with plasma concentrations of another platelet activation marker, β-thromboglobulin (P-TG), it was found that the TSP concentration inei eased exponentially as the plasma β-TG level rose. A positive correlation between plasma levels of plasma TSP and serum fibrin degradation products was also observed. The results suggest that platelets are the primary source of plasma TSP in patients with various vasculitis and that plasma TSP can be a better indicator than β-TG to assess intravascular platelet activation due to its longer circulation half life.

Comparative Plasma Heparin Levels after Subcutaneous Sodium and Calcium Heparin

1978 ◽  
Vol 40 (02) ◽  
pp. 397-406 ◽  
Author(s):  
Joyce Low ◽  
J C Biggs
Keyword(s):  
Peak Plasma ◽  
Plasma Concentrations ◽  
Factor Xa ◽  
Normal Subjects ◽  
Sodium Salts ◽  
Sodium Heparin ◽  
Significant Difference ◽  
Heparin Plasma ◽  
Calcium Heparin ◽  
Plasma Heparin

SummaryComparative plasma heparin levels were measured in normal subjects injected subcutaneously with 5,000 units of the sodium and calcium salts of heparin. Plasma heparin levels were measured up to 7 hr post-injection by an anti-factor Xa assay (Denson and Bonnar 1973). Preliminary studies indicated that heparin levels were reproducible in subjects who received two injections of the same heparin. Peak plasma concentrations (Cmax) and the time at which peak concentration was reached (Tmax) varied greatly from subject to subject. In one group of subjects (15) two commonly used heparins, a sodium heparin (Evans) and a calcium heparin (Choay) were compared. Peak heparin concentrations were not significantly different. However the Tmax for the sodium heparin (1.5 hr) was significantly earlier than the Tmax for the calcium heparin (3 hr) and this was not due to a difference in the volume of the two heparin injections. No significant difference could be detected in the plasma clearance rate and the molecular weight distribution of the two heparins.In two other groups of subjects, sodium and calcium preparations from two manufacturers were compared. In general, the sodium salts gave rise to significantly higher plasma concentrations, which could be interpreted as a greater bioavailability of sodium salts. These results indicate that the salt of the heparin can influence the plasma concentration achieved after subcutaneous injection.

Coagulation and Fibrinolytic Profile of Paediatric Patients Undergoing Cardiopulmonary Bypass

1997 ◽  
Vol 77 (02) ◽  
pp. 270-277 ◽  
Author(s):  
Anthony K C Chan ◽  
Michael Leaker ◽  
Frederick A Burrows ◽  
William G Williams ◽  
Colleen E Gruenwald ◽  
...  
Keyword(s):  
Cardiopulmonary Bypass ◽  
Plasminogen Activator ◽  
Plasma Concentrations ◽  
Factor Xa ◽  
Plasminogen Activator Inhibitor ◽  
Protein S ◽  
Poor Correlation ◽  
Heparin Cofactor Ii ◽  
Paediatric Patients ◽  
Sick Children

SummaryThe haemostatic system and the use of heparin during cardiopulmonary bypass (CPB) have been studied extensively in adults but not in children. Results from adult trials cannot be extrapolated to children because of age-dependent physiologic differences in haemostasis. We studied 22 consecutive paediatric patients who underwent CPB at The Hospital for Sick Children, Toronto. Fibrinogen, factors II, V, VII, VIII, IX, XI, XII, prekallikrein, protein C, protein S, antithrombin (AT), heparin cofactor II, α2-macroglobulin, plasminogen, α2-antiplas- min, tissue plasminogen activator (tPA), plasminogen activator inhibitor, thrombin-AT complexes (TAT), D-dimer, heparin (by both anti-factor Xa assay and protamine titration) and activated clotting time (ACT) were assayed perioperatively. The timing of the sampling was: pre heparin, post heparin, after initiation of CPB, during hypothermia, post hypothermia, post protamine reversal and 24 h post CPB. Plasma concentrations of all haemostatic proteins decreased by an average of 56% immediately following the initiation of CPB due to haemodilution. During CPB, the majority of procoagulants, inhibitors and some components of the fibrinolytic system (plasminogen, α2AP) remained stable. However, plasma concentrations of TAT and D-dimers increased during CPB showing that significant activation of the coagulation and fibrinolytic systems occurred. Mechanisms responsible for the activation of haemostasis are likely complex. However, low plasma concentrations of heparin (<2.0 units/ml in 45% of patients) during CPB were likely a major contributing etiology. ACT values showed a poor correlation (r = 0.38) with heparin concentrations likely due to concurrent haemodilution of haemostatic factors, activation of haemostatic system, hypothermia and activation of platelets. In conclusion, CPB in paediatric patients causes global decreases of components of the coagulation and fibrinolytic systems, primarily by haemodilution and secondarily by consumption.

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