The influence of exogenous magnesium chloride on the apparent INR determined with human, rabbit, and bovine thromboplastin reagents.
Magnesium 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.
van den Besselaar
Anton M H P
AM
Haemostasis and Thrombosis Research Center, Department of Haematology, Leiden University Medical Center, Leiden, The Netherlands. A.M.H.P.van_den_Besselaar@lumc.nl
Witteveen
Evelina
E
Meeuwisse-Braun
Joyce
J
van der Meer
Felix J M
FJ
D000818:Animals; D000925:Anticoagulants / Q000494:pharmacology / Q000627:therapeutic use; D001793:Blood Preservation / Q000379:methods / Q000592:standards; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007202:Indicators and Reagents; D019934:International Normalized Ratio; D015636:Magnesium Chloride / Q000494:pharmacology*; D011517:Prothrombin Time; D011817:Rabbits; D013925:Thromboplastin / Q000592:standards
D000925:Anticoagulants; D007202:Indicators and Reagents; D015636:Magnesium Chloride; D013925:Thromboplastin