scholarly journals Viscoelastometry for detecting oral anticoagulants

2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Philipp Groene ◽  
Daniela Wagner ◽  
Tobias Kammerer ◽  
Lars Kellert ◽  
Andreas Giebl ◽  
...  
Keyword(s):  
Healthy Volunteers ◽  
Prospective Observational Study ◽  
Oral Anticoagulants ◽  
Plasma Concentrations ◽  
Factor Xa ◽  
Clotting Time ◽  
Emergency Situations ◽  
Tissue Plasminogen ◽  
The Impact

Abstract Background Determination of anticoagulant therapy is of pronounced interest in emergency situations. However, routine tests do not provide sufficient insight. This study was performed to investigate the impact of anticoagulants on the results of viscoelastometric assays using the ClotPro device. Methods This prospective, observational study was conducted in patients receiving dabigatran, factor Xa (FXa)-inhibitors, phenprocoumon, low molecular weight heparin (LMWH) or unfractionated heparin (UFH) (local ethics committee approval number: 17–525-4). Healthy volunteers served as controls. Viscoelastometric assays were performed, including the extrinsic test (EX-test), intrinsic test (IN-test) Russel’s viper venom test (RVV-test), ecarin test (ECA-test), and the tissue plasminogen activator test (TPA-test). Results 70 patients and 10 healthy volunteers were recruited. Clotting time in the EX-test (CTEX-test) was significantly prolonged versus controls by dabigatran, FXa inhibitors and phenprocoumon. CTIN-test was prolonged by dabigatran, FXa inhibitors and UFH. Dabigatran, FXa inhibitors and UFH significantly prolonged CTRVV-test in comparison with controls (median 200, 207 and 289 vs 63 s, respectively; all p < 0.0005). Only dabigatran elicited a significant increase in CTECA-test compared to controls (median 307 vs 73 s; p < 0.0001). CTECA-test correlated strongly with dabigatran plasma concentration (measured by anti-IIa activity; r = 0.9970; p < 0.0001) and provided 100% sensitivity and 100% specificity for detecting dabigatran. Plasma concentrations (anti-XA activity) of FXa inhibitors correlated with CTRVV-test (r = 0.7998; p < 0.0001), and CTRVV-test provided 83% sensitivity and 64% specificity for detecting FXa inhibitors. Conclusions In emergency situations, ClotPro viscoelastometric assessment of whole-blood samples may help towards determining the presence and type of anticoagulant class that a patient is taking. Trial registration German clinical trials database ID: DRKS00015302.

scholarly journals Impact of Idarucizumab and Andexanet Alfa on DOAC Plasma Concentration and ClotPro® Clotting Time: An Ex Vivo Spiking Study in A Cohort of Trauma Patients

2021 ◽  
Vol 10 (16) ◽  
pp. 3476
Author(s):  
Daniel Oberladstätter ◽  
Christoph J. Schlimp ◽  
Johannes Zipperle ◽  
Marcin F. Osuchowski ◽  
Wolfgang Voelckel ◽  
...  
Keyword(s):  
Plasma Concentration ◽  
Healthy Volunteers ◽  
Oral Anticoagulants ◽  
Direct Oral Anticoagulants ◽  
Factor Xa ◽  
Factor Xa Inhibitors ◽  
Clotting Time ◽  
Andexanet Alfa ◽  
The Impact

Specific antagonists have been developed for the reversal of direct oral anticoagulants (DOAC). We investigated the impact of these reversal agents on the plasma concentration and visco-elastic test results of dabigatran and factor Xa inhibitors. After baseline measurements of dabigatran, the plasma concentration, and the visco-elastic ClotPro® ecarin clotting time (ECA-CT), we added the reversal agent Idarucizumab in vitro and these two analyses were repeated. Likewise, the baseline plasma concentration of apixaban, edoxaban, and rivaroxaban as well as ClotPro® Russell’s viper venom test clotting time (RVV-CT) were measured and reanalyzed following Andexanet alfa spiking. We analyzed fifty blood samples from 37 patients and 10 healthy volunteers. Idarucizumab decreased the measured dabigatran plasma concentration from 323.9 ± 185.4 ng/mL to 5.9 ± 2.3 ng/mL and ECA-CT from 706.2 ± 344.6 s to 70.6 ± 20.2 s, (all, p < 0.001). Andexanet alfa decreased the apixaban concentration from 165.1 ± 65.5 ng/mL to 9.8 ± 8.1 ng/mL, edoxaban from 152.4 ± 79.0 ng/mL to 36.4 ± 19.2 ng/mL, and rivaroxaban from 153.2 ± 111.8 ng/mL to 18.1 ± 9.1 ng/mL (all p < 0.001). Andexanet alfa shortened the RVV-CT of patients with apixaban from 239.2 ± 71.7 s to 151.1 ± 30.2 s, edoxaban from 288.2 ± 65.0 s to 122.7 ± 37.1 s, and rivaroxaban from 225.9 ± 49.3 s to 103.7 ± 12.1 s (all p < 0.001). In vitro spiking of dabigatran-containing blood with Idarucizumab substantially reduced the plasma concentration and ecarin-test clotting time. Andexanet alfa lowered the concentration of the investigated factor Xa-inhibitors but did not normalize the RVV-CT. In healthy volunteers’ blood, Idarucizumab spiking had no impact on ECA-CT. Andexanet alfa spiking of non-anticoagulated blood prolonged RVV-CT (p = 0.001), potentially as a consequence of a competitive antagonism with human factor Xa.

scholarly journals Chromogenic anti-Xa test: the ratio between heparin activity units and concentration of apixaban and rivaroxaban

2020 ◽  
pp. 96-104
Author(s):  
E. V. Titaeva ◽  
A. B. Dobrovolsky
Keyword(s):  
Oral Anticoagulants ◽  
Direct Oral Anticoagulants ◽  
Plasma Concentrations ◽  
Factor Xa ◽  
Activity Test ◽  
Formation Dynamics ◽  
Test Version ◽  
Heparin Activity ◽  
The Relationship ◽  
Thrombin Formation

Introduction. The direct oral anticoagulants (DOC) therapy does not require alaboratory control; however, it may be required to determine the anticoagulationlevel to choose a treatment strategy if alarge bleeding is developing or emergency surgery is needed.The objective of this experimental study was to investigate the relationship between the residual factor Xa (FXa) activity, anti-Xa activity units oflow molecular weight heparins (LMWH), and the apixaban and rivaroxaban plasma concentrations in a chromogenic anti-Xa assay.Material and methods. Concentrated DOC solutions were prepared by extracting apixaban and rivaroxaban from crushed tablets using methanol and dimethyl sulfoxide, respectively. The resulting solutions were added to the donor plasma pool until final inhibitor concentrations are achieved in the range from 10 to 100 ng/ml plasma. Anti-Xa activity was determined using an STA-compact analyser and the Liquid anti-Xa reagent kit, an analysis protocol, and calibrators designed to control the LMWH therapy. The effect on the thrombin formation dynamics was investigated using the thrombin generation test (TGT) and the PPR reagent as a trigger (final concentrations of tissue factor are 5 pM, and those of phospholipids are 4 μM). TGT curves were analysed using the Thrombinoscope program.Results. It was shown that in the anti-Xa activity test version designed to control the LMWH therapy, there is a high correlation (R2 > 0.98) between thelogarithm of the residual factor Xa activity and the content of apixaban and rivaroxaban in the range from 10 to 80 ng/ml. Rivaroxaban shows about 1.5 times more anti-Xa activity than apixaban at equal concentrations. It was also shown that apixaban and rivaroxaban at doses equal both in concentration and in anti-Xa activity differ in their effect on the thrombin formation dynamics and thrombin inactivation in the TGT.Conclusion. In the LMWH anti-Xa activity test version, the measured range of apixaban and rivaroxaban includes 30 ng/ml and 50 ng/ ml concentrations taken as “cut-off points” to determine the treatment tactics in emergency cases. However, thelack of certified DOC calibratorslimits the use of this test in clinical practice.

Impact of Apixaban On a Large Panel of Routine or More Specific Coagulation Assays.

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 2275-2275
Author(s):  
Jonathan Douxfils ◽  
François Mullier ◽  
Christian Chatelain ◽  
Bernard Chatelain ◽  
Dogné Jean-Michel
Keyword(s):  
Atrial Fibrillation ◽  
Drug Concentration ◽  
Partial Thromboplastin Time ◽  
Factor Xa ◽  
Activated Partial Thromboplastin Time ◽  
Plasma Drug Concentration ◽  
Thrombin Time ◽  
Plasma Drug ◽  
Clotting Time

Abstract Abstract 2275 Introduction: Apixaban is direct factor-Xa inhibitor that reached the market for the prevention of venous thromboembolism in patients undergoing major orthopaedic surgery. It is also being evaluated in the reduction of recurrent ischemic events when added to antiplatelet therapy after an acute coronary syndrome and in the prevention of stroke in patients with non-valvular atrial fibrillation. Thanks to its predictable pharmacokinetic profile, biological monitoring is not required. Nevertheless, evaluation of plasma drug concentration may be valuable in specific situations such as recurrent thrombosis, bleedings, before urgent surgery, in case of bridging and in case of at least two risk factors among the following ones: drug interactions with caution, moderate renal impairment and moderate hepatic impairment; Monitoring may also be useful in infants, pregnant women or in extreme body weights, although no relevant data on drug levels associated with approximate therapeutic and harmful ranges are currently available. Material and Methods: Apixaban was spiked at increasing concentrations (0, 5, 10, 20, 50, 100, 200 and 500 ng/mL) in pooled citrated normal human platelet poor plasma (PPP) to measure Prothrombin Time (PT) and dilute PT with different thromboplastin, Thrombin Generation Assay (TGA) with different inducers and activity on different anti-Xa chromogenic assays. Activated Partial Thromboplastin Time with different reagents, Thrombin Time (TT), Ecarin Clotting Time (ECT) and Reptilase Time (RT), measurement of fibrinogen (Clauss method and PT-derived method) and antithrombin (anti-IIa and anti-Xa based chromogenic assays) were also tested. We also evaluated the impact of apixaban on assays used for the determination of lupus anticoagulant such as the DRVV-T.. (Screen and Confirm) as well as the PTT-LA.. and the Staclot-LA.. . Results and Discussion: As mentioned in previous studies, PT showed a weak sensitivity towards apixaban in comparison with the plasma range obtained in short pharmacokinetic studies. Indeed, the concentration needed to double the clotting time was 154 ng/mL with the most sensitive reagent while the mean Cmax obtained in a short PK study after one oral intake of 5 mg apixaban (dose given in atrial fibrillation) was 96 ng/mL. Therefore, the sensitivity of PT is not strong enough to allow accurate quantitative measurement of the plasma drug concentration (Table 1). Activated Partial Thromboplastin Time presented a better sensitivity but showed a plateau after 100 ng/mL reflecting the uselessness of this test for the quantification of apixaban. Thrombin Time, ECT and RT were logically not affected while DRVV-T.. showed a sensitivity of 205 ng/mL (Screen), which is once again not enough sensitive. On the opposite, chromogenic anti-Xa assays seemed to be very sensitive (Figure 2 and Table 1). Nevertheless, the relation was not always linear and some methodologies needed to be adapted to ensure a broader range of application. TGA (Figure 1) may be useful to assess the pharmacodynamics effects of apixaban on the coagulation process. Nevertheless, the turn around time and the lack of standardisation are currently limitations that restrict the use of this method. In the case of the exploration of an haemorrhagic event, specific tests such as RT, fibrinogen (Clauss and PT-derived method (dFib)), TT and clotting factor activity may be used. Apixaban did not interfere with these tests. Antithrombin determination if also of importance and chromogenic anti-IIa based assays should be used in face of patients treated with apixaban to avoid misdiagnosis since an overvaluation of 12% by 100 ng/mL was shown using one chromogenic anti-Xa based assay. Conclusion: PT may not be used as screening test to assess the risk of bleedings. A more specific and sensitive assay such as chromogenic anti-Xa assays using calibrators should be used to correctly assess the concentration of apixaban. Determination of lupus anticoagulant using DRVV-T.. and PTT-LA.. or Staclot LA.. as well as the determination of antithrombin using factor-Xa based chromogenic assays, were influenced by apixaban. Finally, standardization of the time between the last intake of apixaban and the sampling is mandatory. Figures: Disclosures: No relevant conflicts of interest to declare.

Pharmacodynamic markers in the early clinical assessment of otamixaban, a direct factor Xa inhibitor

2005 ◽  
Vol 94 (12) ◽  
pp. 1156-1163 ◽  
Author(s):  
Marie-Laure Ozoux ◽  
Valeria Chu ◽  
Kelly Simcox ◽  
Vanessa Marks ◽  
Geneviève Freyburger ◽  
...  
Keyword(s):  
Thrombin Generation ◽  
Plasma Concentrations ◽  
Factor Xa ◽  
The Novel ◽  
Direct Factor ◽  
Clotting Time ◽  
Pharmacodynamic Markers ◽  
High Concentrations ◽  
Male Subjects

SummaryThis manuscript reports the assessment of pharmacodynamic (PD) markers of anti-coagulation in the first-in-man study with the novel direct Factor Xa (FXa) inhibitor, otamixaban, with a brief description of safety and pharmacokinetic (PK) findings. The study comprised ten consecutive parallel groups of healthy male subjects (6 active, 2 placebo per group). Eight groups received escalating intravenous doses of otamixaban as 6-hour infusions (1.7 to 183 μg/kg/h) and two groups received a bolus dose (30 or 120 μg/kg) with a 6-hour infusion (60 or 140 μg/ kg/h, respectively). PD markers included anti-FXa activity and clotting time measurements, i.e. activated Thromboplastin Time (aPTT), ProthrombinTime (PT), Heptest® ClottingTime (HCT), and Russell’s Viper Venom-induced clotting Time (RVVT). In addition, Endogenous Thrombin Potential (ETP) was assessed in the bolus-plus-infusion dose groups. Otamixaban was well tolerated. Otamixaban plasma concentrations increased with escalating dose, were maximal at the end-of-infusion (Ceoi), and decreased rapidly as the infusion was stopped. Anti-FXa activity coincided with otamixaban plasma concentrations and clotting time measurements followed the same pattern. Maximal changes from baseline at Ceoi were 1.9 ± 0.2 for aPTT, 2.0 ± 0.2 for PT, 5.1 ± 0.6 for HCT, and 4.5 ± 1.2 for RVVT. Otamixaban inhibited thrombin generation (24% decrease in ETP) and a delay in thrombin generation was noticed in vitro at high concentrations.

Managing reversal of direct oral anticoagulants in emergency situations

2016 ◽  
Vol 116 (12) ◽  
pp. 1003-1010 ◽  
Author(s):  
Harry R. Büller ◽  
Anna Falanga ◽  
Werner Hacke ◽  
Jeroen Hendriks ◽  
Trudie Lobban ◽  
...  
Keyword(s):  
Task Force ◽  
Oral Anticoagulants ◽  
Direct Oral Anticoagulants ◽  
Factor Xa ◽  
Therapeutic Benefit ◽  
Current Status ◽  
Reversal Agent ◽  
Medical Specialties ◽  
Reversal Agents ◽  
Emergency Situations

SummaryAnticoagulation is the cornerstone of prevention and treatment of venous thromboembolism (VTE) and stroke prevention in patients with atrial fibrillation (AF). However, the mechanisms by which anticoagulants confer therapeutic benefit also increase the risk of bleeding. As such, reversal strategies are critical. Until recently, the direct oral anticoagulants (DOACs) dabigatran, rivaroxaban, apixaban, and edoxaban lacked a specific reversal agent. This report is based on findings from the Anticoagulation Education Task Force, which brought together patient groups and professionals representing different medical specialties with an interest in patient safety and expertise in AF, VTE, stroke, anticoagulation, and reversal agents, to discuss the current status of anticoagulation reversal and fundamental changes in management of bleeding associated with DOACs occasioned by the approval of idarucizumab, a specific reversal agent for dabigatran, as well as recent clinical data on specific reversal agents for factor Xa inhibitors. Recommendations are given for when there is a definite need for a reversal agent (e.g. in cases of life-threatening bleeding, bleeding into a closed space or organ, persistent bleeding despite local haemostatic measures, and need for urgent interventions and/or interventions that carry a high risk for bleeding), when reversal agents may be helpful, and when a reversal agent is generally not needed. Key stakeholders who require 24–7/around-the-clock access to these agents vary among hospitals; however, from a practical perspective the emergency department is recommended as an appropriate location for these agents. Clearly, the advent of new agents requires standardised protocols for treating bleeding on an institutional level.

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.

scholarly journals Targeted LC-MS/MS platform for the comprehensive determination of peptides in the kallikrein-kinin system

2021 ◽  
Author(s):  
Tanja Gangnus ◽  
Bjoern B. Burckhardt
Keyword(s):  
Healthy Volunteers ◽  
Clinical Symptoms ◽  
Matrix Effects ◽  
Accurate Determination ◽  
Kinin System ◽  
Carry Over ◽  
Kallikrein Kinin System ◽  
The Impact

AbstractThe kallikrein-kinin system (KKS) is involved in many physiological and pathophysiological processes and is assumed to be connected to the development of clinical symptoms of angioedema or COVID-19, among other diseases. However, despite its diverse role in the regulation of physiological and pathophysiological functions, knowledge about the KKS in vivo remains limited. The short half-lives of kinins, their low abundance and structural similarities and the artificial generation of the kinin bradykinin greatly hinder reliable and accurate determination of kinin levels in plasma. To address these issues, a sensitive LC-MS/MS platform for the comprehensive and simultaneous determination of the four active kinins bradykinin, kallidin, des-Arg(9)-bradykinin and des-Arg(10)-kallidin and their major metabolites bradykinin 2-9, bradykinin 1-7 and bradykinin 1-5 was developed. This platform was validated according to the bioanalytical guideline of the US Food and Drug Administration regarding linearity, accuracy, precision, sensitivity, carry-over, recovery, parallelism, matrix effects and stability in plasma of healthy volunteers. The validated platform encompassed a broad calibration curve range from 2.0–15.3 pg/mL (depending on the kinin) up to 1000 pg/mL, covering the expected concentrations in disease states. No source-dependent matrix effects were identified, and suitable stability of the analytes in plasma was observed. The applicability of the developed platform was proven by the determination of endogenous levels in healthy volunteers, whose plasma kinin levels were successfully detected in the low pg/mL range. The established platform facilitates the investigation of kinin-mediated diseases (e.g. angioedema, COVID-19) and enables the assessment of the impact of altered enzyme activities on the formation or degradation of kinins. Graphical abstract

scholarly journals Development of an approach to cadastral valuation of real estate in areas of possible manifestations of natural disasters and emergency situation

2020 ◽  
Vol 26 (1) ◽  
pp. 190-202
Author(s):  
Alexey Dubrovsky ◽  
Tamara Vereshchaka ◽  
Pavel Batin ◽  
Olesya Malygina
Keyword(s):  
Real Estate ◽  
Urban Policy ◽  
Emergency Situation ◽  
Emergency Situations ◽  
Insurance Funds ◽  
Definition Of ◽  
The Cost ◽  
The Impact ◽  
The City

The article presents the results of studies on the adjustment of cadastral value using a new factor-the probability of an emergency or natural disaster. A new term, emergency geospatial, has been introduced for the spatial definition of an emergency. The analysis of the legal regime of lands subject to emergency situations is carried out. Conclusions are drawn about the legal definition of the geospatial boundary of the emergency situation and the impact of emergencies on real estate. The characteristic of emergency situations, as well as the probability of their occurrence is given. The connection between the emergency situation and the cadastral value of real estate is shown. The dependence of the value of real estate on their location in the geospatial probable emergency. The technological scheme of determination of cadastral value of real estate objects in the zone of manifestation of an emergency situation is developed. A geoinformation project was carried out on the territory of the city of Novosibirsk. The most probable emergencies are taken into account. The map of zones of possible manifestation of emergency situations is made. The comparison of the cost of real estate in emergency zones, with objects analogues, located outside the emergency zone. The values of the correction factor for adjusting the cadastral value are proposed. The map of distribution of correction factors for adjustment of cadastral value of real estate objects in zones of possible manifestation of emergency situations is made. Work on the adjustment of the cadastral value of real estate located in the areas of possible manifestations of emergency situations is promising. First, the zones must be taken into account in modern urban policy and as much as possible to protect real estate and the population from the manifestation of emergency situations. Secondly, the reduction of cadastral value and taxes will allow owners to invest in insurance funds and insure real estate.

scholarly journals Novel Oral Anticoagulants

2010 ◽  
Vol 113 (3) ◽  
pp. 726-745 ◽  
Author(s):  
Jerrold H. Levy ◽  
Nigel S. Key ◽  
Marc S. Azran
Keyword(s):  
Dabigatran Etexilate ◽  
Oral Anticoagulants ◽  
Factor Xa ◽  
Clinical Development ◽  
Thrombin Inhibitor ◽  
Potential Cost ◽  
Replacement Surgery ◽  
Postoperative Setting ◽  
Newer Anticoagulants ◽  
The Impact

Patients undergoing surgery receive anticoagulation for perioperative thromboprophylaxis or ischemic cardiovascular disease. Because anticoagulants may also potentiate bleeding, clinicians need to understand the implications of anticoagulation in perioperative and postoperative patient management. Many newer anticoagulants that are now available or are in clinical development do not require routine coagulation monitoring, have more predictable dose responses, and have fewer interactions with other drugs and food. The most advanced oral anticoagulants in clinical development are the direct factor Xa inhibitors rivaroxaban and apixaban, and the direct thrombin inhibitor dabigatran etexilate. These agents have been evaluated in the postoperative setting in patients undergoing total hip- or knee-replacement surgery with promising results, and it remains to be seen whether these results will translate into other surgical settings. The impact of the new agents will be influenced by the balance between efficacy and safety, improved convenience, and potential cost-effectiveness benefits.

Genetic Modulation of Plasma Protein S Levels by Two Frequent Dimorphisms in the PROS1 Gene

1999 ◽  
Vol 82 (09) ◽  
pp. 1088-1092 ◽  
Author(s):  
J. Duchemin ◽  
M. Levent ◽  
M. Gouault-Heilmann ◽  
C. Leroy-Matheron
Keyword(s):  
Healthy Volunteers ◽  
Allele Frequency ◽  
Total Protein ◽  
Protein S ◽  
Normal Range ◽  
Additional Tool ◽  
Genetic Modulation ◽  
The Impact ◽  
Age And Sex

SummaryWe studied two polymorphisms located close to or within the 3’-untranslated (3’-UT) region of the PROS1 gene [an A to G transition at nt 2148 (Pro 626) and an A to C substitution at nt 2698] in 110 healthy volunteers. The allele frequency of the nt 2148 G variant was 35%, and that of the nt 2698 A variant was 27%. We found a relationship between the two dimorphisms (both separately and together) and the plasma total protein S antigen (tPS) level. The impact of the neutral Pro 626 dimorphism was more significant than that of nt 2698 C/A (p = 0.0003 and p = 0.013, respectively). The lowest tPS values were observed in subjects with the Pro 626;nt 2698 GG;CC genotype, and the highest values in those with the AA;AA genotype. Both polymorphisms acted independently of sex and age. The mechanisms by which the two polymorphisms regulate tPS synthesis were not revealed by the studies of platelet mRNA. This study provides the first evidence of a genetic modulation of tPS levels, which, in addition to age and sex, contributes to the wide normal range of tPS in plasma. Determination of these two polymorphisms could be a valuable additional tool for studying PS.

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