Evaluation of Three Methods for Plasma Fibrinogen Determination

The determination of plasma fibrinogen as clottable protein, as precipitable protein, and by the reaction rate in the conversion of fibrinogen to fibrin is evaluated in terms of the principles of analysis, normal ranges, reproducibility, reliability, and the influence of physiologic antagonists. Comparison of the values obtained from a normal population indicated that the mean value determined by the turbidimetric method was significantly lower than the values obtained by either the clottable protein assay or the conversion reaction rate. However, repeated assays performed on pooled plasma showed comparable reproducibility of the three methods. Physiologic antagonists such as heparin, lipemia, and antithrombin VI affected the turbidimetric method to the greatest extent, but also significantly affected the conversion reaction rate; the clottable protein assay appeared to be the least affected.