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 re-sulting 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 compara-tive standardization by use of a conventional spec-trophotometer. The nephelometer is more sensi-tive and gives a linear response over a wide range of concentrations. Representative information supporting the broad clinical utility of the deter-mination of plasma fibrinogen is illustrated. These assays should be a significant complement to muititest biochemical screening of both healthy and hospitalized individuals. Additional Keyphrases diagnostic aids #{149} spectro-photometry and nephelometry compared #{149}stress eval-uation #{149}multitest screening. buffer as diluent Several investigators have concluded that numerous analytical methods for plasma fibrinogen based on turbidimetry of precipitable protein with various salt-fractionation reagents (sodium sulfite, sodium sulfate, ammonium sulfate, phosphate salts, and glycine) are not reliable enough for broad clinical use (1, 2). Hence, if determination of plasma fibrinogen is to achieve its potential usefulness in clinical medicine, more suitable analytical methods must be devised. Among the better referencetechniques are those involving heat precipita-tion and ultraviolet spectrophotometry (3), or clot formation with thrombin coupled with ultraviolet spec-trophotometry (2, 4). Unfortunately, these procedure