Clinical nephelometry. 1. New, accurate, heat-precipitation nephelometric method for rapid determination of plasma fibrinogen.

We have developed an accurate procedure for measurement of plasma fibrinogen. Turbidity resulting from heating (56#{176}C, 20 mm) plasma diluted with a new “zwitterionic” buffered-saline reagent (pH 5.6) is nephelometrically measured (600 nm). We evaluated the method both by confirming the accuracy of its prestandardization and calibration on a new clinical nephelometer, and by comparative standardization by use of a conventional spectrophotometer. The nephelometer is more sensitive and gives a linear response over a wide range of concentrations. Representative information supporting the broad clinical utility of the determination of plasma fibrinogen is illustrated. These assays should be a significant complement to muititest biochemical screening of both healthy and hospitalized individuals.