Clinical hemostasis activation can be very dangerous, e.g. in pathologic disseminated intravascular coagulation (PDIC). Long transport times of this unstable plasma into the hemostasis laboratory or freezing/thawing of the samples induces artefactual hemostasis changes. 308 unselected EDTA plasmas of patients were analyzed for plasmatic amidolytic thrombin activity. EDTA-plasmas of 94 patients were stabilized with 1.25 M plasma concentration arginine and analyzed for plasmatic amidolytic thrombin activity directly or after freezing at -24癈/thawing at room temperature (RT). EDTA-plasmas were supplemented with 0-1100 mM arginine, stored for 24h at RT, and analyzed for plasmatic thrombin activity.The normal donor range of amidolytic thrombin activity in plasma is 100 (+-) 20 % of normal, the overall patient range is 131 (+-) 40 % of normal (mean value (+-) 1 standard deviation); the thrombin activity in patient plasmas distributes normally according to Gauss. Analysis of arginine-stabilized EDTA-plasma prior to or after freezing/thawing correlate with r=0.980, however thrombin activity in unstabilized frozen EDTA-plasma correlates only with r=0.835 to that of stabilized plasma. Addition of EDTA-plasma to arginine correlates with addition of arginine to polystyrol wells that were pre-incubated for 2h with EDTA-plasma (r=0.965). Addition of > 50 mM arginine to plasma increases the stability of thrombin activity after 24h storage at RT in individual plasmas, with an increase of correlation from r=0.824 to r > 0.9.Arginine stabilization of EDTA-plasma enables the analysis of the true hemostasis activation state of a patient even in frozen plasma. This might be of great impact on both diagnosis and therapy of hemostasis disorders.
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