A rapid, sensitive and quantitative spectrophotometric assay of soluble fibrin in
plasma samples has been developed. The method is based on the principle that fibrin
stimulates the activation of plasminogen by tissue plasminogen activator (t-PA). A
sample containing fibrin is incubated with t-PA, plasminogen and a plasmin-sensitive
chromogenic substrate. An increase in absorbance which is dependent on the fibrin
concentration in the sample is obtained. In plasma samples an initial lag-phase, due
to the presence of alpha2-antiplasmin is observed. However, the change in A405 per square minute during the later part of the reaction was found to be proportional
to the fibrin content and to generate linear standard curve intercepts at the origin.
The detection limit of bathroxobin-digested fibrinogen added to plasma was about 5
nmol/L. Recovery experiments at 20 and 75 nmol/L levels in plasma samples from healthy
individuals were excellent. The “within-run” variation (CV) was determined as 3.7%.
The formation of fibrin after addition of minute amounts of thrombin to plasma could
be monitored with the method. Plasma from 8 healthy individuals was found to contain
about 9.2 ± 1.9 nmol/L fibrin. Plasma samples from 46 patients with a suspected haemostatic
disturbance had higher levels of soluble fibrin (53 ± 62 nmol/L). Seven of the 46
samples had concentrations above 150 nmol/L.
Key words
Soluble fibrin - Disseminated intravascular coagulation - Fibrin stimulated plasminogen
activation
