Summary
1. It was found that effects of deliberate changes in fibrinogen concentration and in the amount of FDP added to the experimental system (containing pure fibrinogen solution and saline- or serumdiluted plasma) could be approximated with satisfactory accuracy by a linear plot of the logarithm of clotting times versus the inverse of fibrinogen concentration.
By increasing FDP activity the slope of the obtained lines becomes proportionately steeper. The constants, which interrelate clotting time, fibrinogen concentration and FDP activity, are to be derived experimentally. The obtained formula is expressed also nomographically.
2. Apart from the presence of some very rare anticoagulants, an elongation of thrombin time observed under strictly specified conditions points to a substantial reduction of fibrinogen concentration and/or an interplay of fibrinogen degradation products.
If a definite amount of fibrinogen (Fibrinogen sec. Warner Chilcott) is admixed to a pathological plasma, thrombin time in the latter will decrease in a specifiable manner. By entering the original and corrected thrombin time values in the reported nomogram the fibrinogen content and FDP activity of the pathological plasma can be calculated.
3. The described procedure for fibrinogen and FDP assay is suitable first of all in acute defibrination syndrome and at the thrombolytic therapy. Its agreement with the results obtained by immunodiffusion was satisfactory as regards the fibrinogen in plasmas of different fibrinogen concentration.
