Summary: Protamine sulphate-induced aggregation of soluble fibrin causes an increase of turbidity in the plasma sample, which can be measured by means of kinetic turbidimetry.A method was developed which is sufficiently sensitive for the determination of soluble fibrin in plasma without iüterfering with the sensitivity for fibrinogen. The performance of the assay was studied by analysing plasma samples with high concentrations of fibrinogen and soluble fibrin at different pH values, at different concentrations of plasma and protamine sulphate, and using different wavelengths and analysis times. Measurement of thrombin-induced fibrinogen-fibrin-transformation by the developed turbidimetric method, gave results that correlated well with the release of fibrinopeptide A.The new protamine sulphate method for turbidimetric dclcrmination of soluble fibrin is charactcrizcd by its practicability, rapid availability of reproducible, quantitative results, and ils economy ofreagenls and time in single and serial analysis. Therefore it seems well-suited for the routine diagnosis of hypercoagulability with increased fibrinogen turnover.
The validity of the fibrin(ogen) derivatives 'soluble fibrin, D-dimers and fibrin(ogen) degradation products' was compared with other parameters in early and sensitive diagnosing of disseminated intravascular coagulation (DIC). In a clinical study 900 patients' samples from separate, defined groups were examined, including course observations of intensive care patients (n = 38) and patients with acute pancreatitis. The fibrin(ogen) derivatives correlated very well with the degree of blood coagulation disturbances: in particular, D-dimers and soluble fibrin proved to be more sensitive in early diagnosis of DIC than other parameters. The SF-PS-turbidimetry demonstrated a good validity and practicality in the quantitative determination of soluble fibrin, but a suitable analyzer is essential. Determination of D-dimers is preferable to that of fibrin(ogen) degradation products (both in the latex-agglutination test) because of the better sensitivity and practicality; even more sensitive results were provided by the D-dimer-ELISA, which is, however, not practical in acute diagnostics. The decrease in protein C was at least equally sensitive as the antithrombin III-levels in indicating the consumption of the hemostatic potential. The decrease of thrombocyte counts and fibrinogen levels could first be detected in a later stage of DIC. In conclusion, D-dimers and soluble fibrin can improve the DIC diagnostics, making them more reliable; additionally, antithrombin III and possibly protein C deserve further consideration, although the fibrin(ogen) derivatives are apparently of greater importance.
A new method has been elaborated that shows a high sensitivity for soluble fibrin (SF) in plasma without disturbing sensitivity for fibrinogen; the aggregation of soluble fibrin by protamine sulfate (PS) leads to a turbidity of the plasma sample which is measured by means of turbidimetry.To evaluate the test conditions, plasma samples with high levels of fibrinogen and soluble fibrin were analysed, varying pH value, concentration of plasma and PS, wavelength and timing of the analysis.The SF-PS-turbidimetry correlated well with the fibrinopeptid A levels in plasma samples with thrombin induced fibrinogen-fi-bri n-transformation.This method is characterized by its good practicability, prompt availability of reproducible quantifying results and its economy in single and serial analysis.Analysis of plasma samples from 2000 patients demonstrated the good validity of the new method; it is qualified for routine diagnostics of hypercoagulability with increased fibrinogen turnover.
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