U. Haddeland et al., FIBRINOGEN PRESENT IN EDTA-ANTICOAGULATED PLASMA STIMULATES THE TISSUE-TYPE PLASMINOGEN ACTIVATOR-CATALYZED CONVERSION OF PLASMINOGEN TO PLASMIN, Blood coagulation & fibrinolysis, 5(5), 1994, pp. 767-772
The presence of soluble fibrin in plasma is an early and sensitive ind
icator of activation of the coagulation system. Quantitative spectroph
otometric assays for soluble fibrin can be based on the principle that
soluble fibrin stimulates the tissue-type plasminogen activator-catal
ysed conversion of plasminogen to plasmin. It was previously shown tha
t treatment of purified fibrinogen by EDTA, which removes the three ti
ghtly bound Ca2+ ions, results in exposure of tissue-type plasminogen
activator-catalytic sites similar to those unveiled by thrombin. Since
EDTA is a common anticoagulant, it was of interest to study the effec
t of EDTA on a test based on plasminogen activation. It is concluded t
hat the determination of soluble fibrin in EDTA-anticoagulated plasma
from healthy individuals gives a false positive indication of the pres
ence of soluble fibrin. This was true irrespective of whether the test
was performed at pH 7.4, 7.8 or 8.5. The most probable explanation is
that tissue-type plasminogen activator-stimulating sites are exposed
in fibrinogen by EDTA. Therefore, EDTA-plasma is unsuitable for assayi
ng soluble fibrin with tests based on the tissue-type plasminogen acti
vator-mediated conversion of plasminogen to plasmin.