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

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.

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Comparison between siliconized evacuated glass and plastic blood collection tubes for prothrombin time and activated partial thromboplastin time assay in normal patients, patients on oral anticoagulant therapy and patients with unfractioned heparin therap

International Journal of Laboratory Hematology ◽

10.1111/j.1751-553x.2010.01271.x ◽

2010 ◽

Vol 33 (2) ◽

pp. 219-225 ◽

Cited By ~ 7

Author(s):

G. D’ANGELO ◽

C. VILLA

Keyword(s):

Prothrombin Time ◽

Anticoagulant Therapy ◽

Partial Thromboplastin Time ◽

Oral Anticoagulant ◽

Oral Anticoagulant Therapy ◽

Activated Partial Thromboplastin Time ◽

Blood Collection ◽

Unfractioned Heparin ◽

Blood Collection Tubes

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A comparative study of conventional versus new, magnesium-poor Vacutainer® Sodium Citrate blood collection tubes for determination of prothrombin time and INR

Thrombosis Research ◽

10.1016/j.thromres.2014.04.016 ◽

2014 ◽

Vol 134 (1) ◽

pp. 187-191 ◽

Cited By ~ 8

Author(s):

Anton M.H.P. van den Besselaar ◽

Iris J.H. van Vlodrop ◽

Paul B. Berendes ◽

Christa M. Cobbaert

Keyword(s):

Comparative Study ◽

Prothrombin Time ◽

Sodium Citrate ◽

Blood Collection ◽

Blood Collection Tubes ◽

Citrate Blood

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A Comparison of Two Sodium Citrate Concentrations in Two Evacuated Blood Collection Systems for Prothrombin Time and ISI Determination

Thrombosis and Haemostasis ◽

10.1055/s-0037-1614084 ◽

2000 ◽

Vol 84 (10) ◽

pp. 664-667 ◽

Cited By ~ 18

Author(s):

V. Chantarangkul ◽

A. Tripodi ◽

A. M. H. P. van den Besselaar

Keyword(s):

Prothrombin Time ◽

Sodium Citrate ◽

Oral Anticoagulant Therapy ◽

Oral Anticoagulants ◽

Practical Importance ◽

Blood Collection ◽

Blood Samples ◽

Polyethylene Terephtalate ◽

Glass Tubes ◽

The Difference

SummaryThe prothrombin time is usually measured in citrated plasma. The W.H.O. recommended concentration of sodium citrate for blood collection for laboratory control of oral anticoagulant therapy is 0.109 M. Some evacuated blood collection systems include 0.105 M sodium citrate. The purpose of the present study was to establish the difference in ISI calibration between 0.109 and 0.105 M citrate, using 7 types of thromboplastin and various types of instrumentation. The two citrate concentrations were provided in both evacuated siliconised glass tubes and in evacuated polyethylene terephtalate (PET) tubes. The ISI difference between the two citrate concentrations was 5.4% for one system but not greater than 3% for all other systems when blood samples were collected with either siliconized glass or PET tubes. Most of the ISI differences between the two citrate concentrations were not significant at the 5% level. It is concluded that the ISI differences between 0.105 M and 0.109 M citrate are not of practical importance. In contrast, ISI differences between siliconised glass and PET tubes, using either 0.105 or 0.109 M citrate, were significant (p <0.05) for most thromboplastin systems and amounted to 7%. ISI interchange between these glass and PET tubes could induce INR differences amounting to 14%, which could affect clinical dosage of oral anticoagulants.

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Effect of Laboratory Variation in the Prothrombin-Time Ratio on the Results of Oral Anticoagulant Therapy

New England Journal of Medicine ◽

10.1056/nejm199309023291005 ◽

1993 ◽

Vol 329 (10) ◽

pp. 696-702 ◽

Cited By ~ 40

Author(s):

Mark H. Eckman ◽

Herbert J. Levine ◽

Stephen G. Pauker

Keyword(s):

Prothrombin Time ◽

Anticoagulant Therapy ◽

Oral Anticoagulant ◽

Oral Anticoagulant Therapy ◽

Time Ratio ◽

Prothrombin Time Ratio

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

Hämostaseologie ◽

10.1055/s-0038-1655219 ◽

1993 ◽

Vol 13 (02) ◽

pp. 96-105 ◽

Cited By ~ 2

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.

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The influence of exogenous magnesium chloride on the apparent INR determined with human, rabbit, and bovine thromboplastin reagents

Thrombosis and Haemostasis ◽

10.1055/s-0037-1613541 ◽

2003 ◽

Vol 89 (01) ◽

pp. 43-47 ◽

Cited By ~ 6

Author(s):

Evelina Witteveen ◽

Joyce Meeuwisse-Braun ◽

Felix van der Meer ◽

Anton van den Besselaar

Keyword(s):

Magnesium Chloride ◽

Sodium Citrate ◽

Oral Anticoagulant Therapy ◽

International Normalized Ratio ◽

Bovine Brain ◽

Rabbit Brain ◽

Blood Collection ◽

Bovine Plasma ◽

Different Types ◽

Blood Specimens

SummaryMagnesium ions can shorten the tissue factor-induced coagulation time. Some blood collection systems with sodium citrate are contaminated with variable amounts of magnesium and influence the results of the prothrombin time (PT) test. The aim of the study was to determine the dose-response relationship between exogenous magnesium chloride added to blood and the PT and the international normalized ratio (INR). Blood specimens from twenty patients on oral anticoagulant therapy were investigated. Four different types of thromboplastin reagents were used: recombinant human, human placenta, rabbit brain, and bovine brain combined with adsorbed bovine plasma. With all four reagents, exogenous magnesium induced a reduction of the apparent INR. Bovine thromboplastin was not as responsive to magnesium as the human and rabbit reagents. The magnitude of the INR deviation induced by 0.1 mmol/l magnesium in the blood was smaller than 10% in all patient samples. At 0.5 mmol/l magnesium in the blood, 10-35% of the patient samples had INR deviations greater than 10%, depending on the thromboplastin reagent used.

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