Improved micromethod for plasma fibrinogen unaffected by heparin therapy.

An improved micromethod for plasma fibrinogen, based on the Ellis-Stransky thrombin-clot density procedure, is presented. Modifications includes: (1) addition of Polybrene eliminates heparin interference; (2) measurement of absorbance at 340 nm provides improved sensitivity at low fibrinogen levels as well as with small volumes of plasma (40 mul.); (3) higher concentration of thrombin reduces the incubation time. Plasma fibrinogen by the proposed method compares well with a reference procedure based on total clottable protein (coefficient of correlation 0.99).