Calibration of a Lyophilized Pooled Plasma as Candidate Reference Plasma for Standardization of the Prothrombin Time Ratio

1993 ◽  
Vol 13 (02) ◽  
pp. 96-105 ◽  
Author(s):  
H. Beeser ◽  
U. Becker ◽  
H. J. Kolde ◽  
E. Spanuth ◽  
P. Witt ◽  
...  
Keyword(s):  
Prothrombin Time ◽  
International Study ◽  
International Normalized Ratio ◽  
Measurement Methods ◽  
Factor V ◽  
Diagnostic Instruments ◽  
Plasma Pool ◽  
Normal Plasma ◽  
German Association ◽  
Prothrombin Time Ratio

SummaryThe prothrombin time (PT), obtained from a fresh normal plasma pool (FPP), is the basis both for the establishment of the 100% activity (normal plasma) and for the ratio calculation used in the International Normalized Ratio (INR) according to the recommendations of the ICSH/ICTH (6). Today the PT of lyophilized normal plasma pools are successfully used as reference for the assessment of samples in proficiency studies. However, a lack of comparability is to be recognized. Therefore the Committee of Hematology of the German Association of Diagnostics’ and Diagnostic Instruments’ Manufacturers (VDGH) decided to produce a candidate reference plasma (VDGH Reference Plasma) which was calibrated against fresh normal plasma pools in an international study.The basic calibration was performed by using the same certified BCR thromboplastin (BCT/099) by all participants. The endpoint was determined manually and by using the coagulometer Schnitger-Gross. In additional testings each participant used his own routine thromboplastins and methods. Calculating the ratio [PT VDGH Reference Plasma (sec)/PT fresh normal plasma pool (sec)] the VDGH Reference Plasma showed a deviation from the average fresh normal plasma pool of 1.05 both with the BCT/099 and with all thromboplastins. There were obtained some statistical differences between “plain” and “combined’’ (added factor V and fibrinogen) thromboplastins. No statistical difference was found between the different endpoint measurement methods (manual, mechanical, optical).In spite of these statistical deviations the VDGH Reference Plasma can be used for the standardization of the PT-normal (100%) value with different ratios for plain (1.06) and combined (1.02) thromboplastins. The manufacturers will use this VDGH Reference Plasma for the calibration of their commercially available calibration plasmas, which allows the user of such a material to calculate a calibrated 100% PT value.

Reconstitution Of PF1 In Platelets From Factor V-Deficient Donors As A Function Of Available PF3

1981 ◽  
Author(s):  
A P Bode ◽  
H Sandberg ◽  
F A Dombrose ◽  
B R Lentz
Keyword(s):  
Prothrombin Time ◽  
Human Platelets ◽  
Factor V ◽  
Freezing And Thawing ◽  
One Stage ◽  
Normal Platelet ◽  
Normal Plasma ◽  
Protein Particles ◽  
Induced Aggregation ◽  
Free Plasma

Reconstitution of membrane-associated Factor V-like activity (PF1) in human platelets isolated from severe F.V-deficient donors was assessed following incubations in citrated normal platelet free plasma. Coagulant activities were measured using: a one-stage prothrombin time, the Stypven time and a modified KAPTT in which the kaolin particles were removed from the plasma prior to recalcification. The supernatant from 3x frozen-and-thawed lysed normal platelets was used as a standard for 100% PF1 and 100% PF3. Normal platelets gel filtered or centrifuge-washed in the presence of adenosine, theophylline and PGEj had <1% available PFI and PF3, whereas platelets from severe F.V-deficient donors isolated by the same procedure had no PF1 and the same amount of PF3. The supernatant from 3x frozen-and-thawed lysed F.V-deficient platelets also had no PF1 but had 100% total PF3. When gel filtered, PFl-deficient platelets were incubated in normal plasma, they acquired about 1% PF1 which did not change following freezing-and-thawing. By contrast, PFI-deficent platelets washed in the absence of these inhibitors had 15-20 times more available PF3 and acquired about 15-20 times more total PFI after incubation in normal plasma. When either the crude frozen-and-thawed lysed membrane supernatant from these PFl-deficient platelets (100% available PF3) or a partially purified membrane-rich fraction from this supernatant was incubated with normal plasma, then 100% reconstitution of PFI was achieved. PF1 was also reconstituted in a purified system using all-or-none binding when the PF3-containing lipid-protein particles secreted by platelets, upon collagen induced aggregation, were incubated with purified human F.Va. Following incubation, these particles had the same amount of PFI as the PF3-containing particles from normal platelets. It is apparent that in human platelets a correlation exists between the amount of available PF3 and the capacity to reconstitute PFI.

scholarly journals Complications of warfarin therapy monitored by the international normalized ratio versus the prothrombin time ratio

1995 ◽  
Vol 18 (2) ◽  
pp. 80-82 ◽  
Author(s):  
Thomas C. Andrews ◽  
David W. Peterson ◽  
Dennis Doeppenschmidt ◽  
Jeff S. Foster ◽  
Michael J. Lucca ◽  
...  
Keyword(s):  
Prothrombin Time ◽  
Warfarin Therapy ◽  
International Normalized Ratio ◽  
Time Ratio ◽  
Ratio Versus ◽  
Prothrombin Time Ratio

scholarly journals Simplified Method for International Normalized Ratio (INR) Derivation Based on the Prothrombin Time/INR Line: An International Study

2010 ◽  
Vol 56 (10) ◽  
pp. 1608-1617 ◽  
Author(s):  
Leon Poller ◽  
Saied Ibrahim ◽  
Michelle Keown ◽  
Albert Pattison ◽  
Jørgen Jespersen
Keyword(s):  
Prothrombin Time ◽  
Independent Set ◽  
International Study ◽  
International Normalized Ratio ◽  
Sensitivity Index ◽  
Concerted Action ◽  
Total Proportion ◽  
The Mean ◽  
Certified Values ◽  
International Sensitivity Index

BACKGROUND The need to perform local International Sensitivity Index (ISI) calibrations and in particular the requirement for a manual method for prothrombin time (PT) determination, have proved to be obstacles to application of the WHO scheme for PT standardization. METHODS We used international normalized ratio (INR) derived with a set of only 5 European Concerted Action on Anticoagulation (ECAA) lyophilized calibrant plasmas, certified manually by expert centers with reference thromboplastins, to determine a local PT/INR Line. We compared results of an independent set of validation plasmas with INRs from conventional ISI calibrations and with manually certified INRs. RESULTS The mean certified INR of 5 lyophilized validation plasmas was 2.41 with human thromboplastin, 2.04 with bovine/combined, and 2.80 with rabbit. With 42 human reagents, the mean observed INR of the validation plasmas was 2.68 (11.2% deviation from certified INR). Deviation was reduced to 0.4% with both local ISI calibration and the PT/INR Line. Eight results based on bovine/combined thromboplastin gave an INR deviation of 4.9%, becoming 0.5% after ISI calibration and 2.4% with the PT/INR Line. Six results with rabbit reagents deviated from certified INR by 2.5%. After ISI calibration, deviation became 1.1%, and with the PT/INR Line, 0.7%. The PT/INR Line gave similar results with both linear and orthogonal regression analysis. The total proportion of validation plasmas giving INR within 10% deviation from certified values was 42.5% with uncorrected INR, which increased to 92.1% with local ISI calibration and 93.2% with the PT/INR Line. CONCLUSIONS The PT/INR Line procedure with 5 ECAA calibrant plasmas successfully substitutes for local ISI calibrations in deriving reliable INRs.

scholarly journals Features of the hemostasis system in patients with non-alcoholic fatty liver disease

2021 ◽  
Vol 55 (4) ◽  
pp. 235-238
Author(s):  
V.I. Didenko ◽  
S.L. Melanich ◽  
V.B. Yagmur ◽  
K.A. Ruban
Keyword(s):  
Liver Disease ◽  
Fatty Liver ◽  
Prothrombin Time ◽  
Hepatic Steatosis ◽  
Fatty Liver Disease ◽  
International Normalized Ratio ◽  
Alcoholic Fatty Liver ◽  
Hemostasis System ◽  
Alcoholic Fatty Liver Disease ◽  
Prothrombin Time Ratio

Background. Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease. In recent years, disorders in the hemostasis system, their role in the progression of liver diseases and the development of cardiovascular complications in NAFLD have been actively studied. The purpose was to investigate the features of the hemostasis system in patients with non-alcoholic fatty liver disease. Materials and methods. We examined 36 individuals with NAFLD (20 women and 16 men) aged 29–73 years. All patients underwent an anthropometric, general clinical, biochemical study of blood serum with the determination of platelets, prothrombin time ratio, international normalized ratio, fibrinogen, ultrasound examination of the abdominal cavity organs with elastometry, followed by statistical data processing. Results. Among patients with NAFLD, class 2 obesity and overweight (30.6 % each), class 1 obesity (27.8 %) prevailed. At the same time, according to the controlled attenuation parameter, 38.9 % of people had a severe degree of steatosis, 33.3 % — moderate and 27.8 % — mild. Regarding the indicators of hemostasis, a significant increase in the level of fibrinogen up to (4.9 ± 0.5) g/l was detected in 44.4 % of patients, its severity tended to grow with an increase in the degree of hepatic steatosis. Conclusions. In 44.4 % of NAFLD patients, with an increase in the degree of hepatic steatosis, the tendency to hypercoagulability has grown with an increase in fibrinogen content by 1.6 times (p < 0.001). Changes in the international normalized ratio, prothrombin time ratio and platelets were determined in isolated cases: more than 83.3 % of patients with NAFLD didn’t have violations of these parameters.

Prothrombin Time Ratio Is Reduced by Magnesium Contamination in Evacuated Blood Collection Tubes

2001 ◽  
Vol 85 (04) ◽  
pp. 647-650 ◽  
Author(s):  
W. van Dam ◽  
A. Sturk ◽  
R. M. Bertina ◽  
A. M. H. P. van den Besselaar
Keyword(s):  
Prothrombin Time ◽  
Sodium Citrate ◽  
Oral Anticoagulant Therapy ◽  
Blood Collection ◽  
Magnesium Ions ◽  
Time Ratio ◽  
Normal Plasma ◽  
The Mean ◽  
Blood Collection Tubes ◽  
Prothrombin Time Ratio

SummaryMagnesium ions were detected in sodium citrate solutions in several lots of evacuated blood collection tubes. The mean concentrations ranged between 1.3 and 1.6 mmol/L. Magnesium was also present in the rubber stoppers of the blood collection tubes and could be leached into the citrate solution. It was shown that magnesium added to citrated plasma shortened the prothrombin time of both coumarin and normal plasma. The effect of magnesium was relatively greater on coumarin than on normal plasma resulting in reduced prothrombin time ratio. Shortening of the prothrombin time was also observed when magnesium chloride was added to dialysed plasma, i.e., in the absence of citrate. These results indicate that magnesium contamination can interfere with accurate INR determination in the control of oral anticoagulant therapy.

Factor V Inhibitor Developing After Liver Transplantation in a 3-Year-Old Child

PEDIATRICS ◽  
1991 ◽  
Vol 88 (1) ◽  
pp. 156-159
Author(s):  
BRUCE GORDON ◽  
WILLIAM HAIRE ◽  
MICHAEL DUGGAN ◽  
ALAN LANGNAS ◽  
BYERS SHAW
Keyword(s):  
Liver Transplantation ◽  
Factor Viii ◽  
Prothrombin Time ◽  
Blood Coagulation ◽  
Partial Thromboplastin Time ◽  
Factor V ◽  
Bleeding Tendency ◽  
Normal Plasma ◽  
Surgical Operations

Acquired inhibitors of blood coagulation have been recognized with increasing frequency since the classic review by Margolius et al in 1961.1 The most common acquired inhibitor is directed against factor VIII and usually arises in patients with classical hemophilia.2 Inhibitors directed against factor V are considered rare; only 30 cases have been reported in the literature.3-6 The majority of these cases occur in patients olden than 60 years and many have arisen following major surgical operations. Patients present with variable bleeding tendency and a prolonged partial thromboplastin time (PTT) and prothrombin time (PT), which fail to correct with the addition of normal plasma.

Prothrombin Determination by Means of a Chromogenic Peptide Substrate

1975 ◽  
Author(s):  
K. Korean-Bengtsen ◽  
G. Axelsson
Keyword(s):  
Prothrombin Time ◽  
Linear Relationship ◽  
Optical Density ◽  
Present Method ◽  
Reading Time ◽  
Rabbit Brain ◽  
Factor V ◽  
Chromogenic Substrate ◽  
Peptide Substrate ◽  
Normal Plasma

A two stage method to determine prothrombin with a chromogenic peptide substrate benzoyl-phe-val-arg-p-nitroanilid (Bofors, Göteborg, Sweden) has been worked out. Citrated plasma (10 μl) was diluted in 600 μl tris buffer pH = 8.2 μ 0.15 and activated with 250 μl of a commercial rabbit brain-lung thromboplastin (Simplastin, General Diagnostics Division, Warner-Lambert, Morris Plain, U.S.A.) After 5 minutes incubation at 37° C 200 μl of a 1 mM solution of the chromogenic substrate was added and the increase in optical density was recorded in a LKB-Beckman 8000 enzyme analyzer. A reading time of 1 minute was used which permitted 60 analyses per hour to be carried out. A linear relationship was found between ΔOD and dilutions of normal plasma in prothrombin deficient plasma or adsorbed plasma. The method is insensitive to variations in factor V, VII and X. Less than 5% of normal plasma was needed to “normalize” plasmas deficient in factor V or VII or X. The method can be used to control dicumarol treatment. A group if dicumarol treated patients has been investigated with the present method and with Quick’s prothrombin time and with a P & P-method using Simplastin A (General Diagnostics Division, Warner-Lambert, Morris Plains, U.S.A.) as a reagent. The results of this comparison is presented.

INR calibration of Owren-type prothrombin time based on the relationship between PT% and INR utilizing normal plasma samples

2004 ◽  
Vol 91 (06) ◽  
pp. 1223-1231 ◽  
Author(s):  
Nils Egberg ◽  
Andreas Hillarp ◽  
Ole Ødegaard ◽  
Bror Edlund ◽  
Jan Svensson ◽  
...  
Keyword(s):  
Prothrombin Time ◽  
Oral Anticoagulant Therapy ◽  
Calibration Procedure ◽  
International Normalized Ratio ◽  
Plasma Samples ◽  
Who Guidelines ◽  
Healthy Individuals ◽  
Normal Plasma ◽  
Warfarin Treatment ◽  
The Relationship

SummaryProthrombin time (PT) is clinically important and is used to monitor oral anticoagulant therapy. To obtain PT results in international normalized ratio (INR), the current standardization procedure is complex and involves reference reagents.The PT of diluted plasma samples can be determined with a combined thromboplastin (the Owren-type procedure), but not necessarily with a plain thromboplastin (the Quick-type procedure). Owren-type PT procedures can therefore, as an alternative to the INR calibration, be calibrated with diluted normal plasma to give PT results in percent of normal PT activity (PT%).The present study explored if a plasma-based calibration of an Owren-type PT procedure can be used to obtain results in INR. The approach was to establish a relationship between PT% and INR by multi-center analysis of 365 samples from healthy individuals and patients on warfarin treatment. INR values were obtained by manual Quick-type reference procedure and PT% values by various automated Owren-type procedures. A relationship INR = (1/PT% + 0.018)/0.028 was found. A calibration procedure, based on the relationship, was investigated. Calibrators were the median PT of 21 normal plasma at dilutions representing 100%, 50%, 25%, 12.5% and 6.25% of normal PT activity. These were assigned INR values of 1.00, 1.36, 2.07, 3.05 and 6.36. Calibration of various Owren-type assays was repeatedly performed by 5 expert laboratories during 3 consecutive years. The INR values of certain lyophilised or frozen control plasmas were determined. The frozen control plasmas had externally assigned INR values according to WHO guidelines. Within the laboratory, CV was typically below 3%. No appreciable difference among the results of the different laboratories or the three assay occasions was found. Externally assigned and INR values were essentially identical to those found. These and other results indicated that the calibration procedure was reproducible, precise and accurate. Thus, an Owren-type PT assay can be calibrated with normal plasma samples to give results in INR and the investigated calibration procedure can be proposed for this purpose.

Heparin and Low Molecular Weight Heparins Inhibit Prothrombinase Formation but not its Activity in Plasma

1994 ◽  
Vol 72 (06) ◽  
pp. 862-868 ◽  
Author(s):  
Frederick A Ofosu ◽  
J C Lormeau ◽  
Sharon Craven ◽  
Lori Dewar ◽  
Noorildan Anvari
Keyword(s):  
Factor Xa ◽  
Catalytic Efficiency ◽  
Thrombin Inhibitor ◽  
Lag Phase ◽  
Factor V ◽  
Factor X ◽  
Normal Plasma ◽  
Plasma Factor ◽  
Prothrombin Activation ◽  
Plasma Heparin

SummaryFactor V activation is a critical step preceding prothrombinase formation. This study determined the contributions of factor Xa and thrombin, which activate purified factor V with similar catalytic efficiency, to plasma factor V activation during coagulation. Prothrombin activation began without a lag phase after a suspension of coagulant phospholipids, CaCl2, and factor Xa was added to factor X-depleted plasma. Hirudin, a potent thrombin inhibitor, abrogated prothrombin activation initiated with 0.5 and 1.0 nM factor Xa, but not with 5 nM factor Xa. In contrast, hirudin did not abrogate prothrombin activation in plasmas pre-incubated with 0.5,1.0 or 5 nM α-thrombin for 10 s followed by the coagulant suspension containing 0.5 nM factor Xa. Thus, thrombin activates plasma factor V more efficiently than factor Xa. At concentrations which doubled the clotting time of contact-activated normal plasma, heparin and three low Mr heparins also abrogated prothrombin activation initiated with 0.5 nM factor Xa, but not with 5 nM factor Xa. If factor V in the factor X-depleted plasma was activated (by pre-incubation with 10 nM a-thrombin for 60 s) before adding 0.5,1.0, or 5 nM factor Xa, neither hirudin nor the heparins altered the rates of prothrombin activation. Thus, none of the five anticoagulants inactivates prothrombinase. When 5 or 10 pM relipidated r-human tissue factor and CaCl2 were added to normal plasma, heparin and the three low Mr heparins delayed the onset of prothrombin activation until the concentration of factor Xa generated exceeded 1 nM, and they subsequently inhibited prothrombin activation to the same extent. Thus, hirudin, heparin and low Mr heparins suppress prothrombin activation solely by inhibiting prothrombinase formation.

Sign in / Sign up

Export Citation Format

Share Document