Can Heparin Plasma Be Used Instead of Serum for Nephelometric Analysis of Serum Proteins?(Letters) (Letter to the Editor‪)‬

To the Editor: Nephelometry is widely used for quantification of serum proteins. The main manufacturers of nephelometers, Beckman-Coulter and DadeBehring, recommend serum as a sample for most tests. For a limited number of tests, e.g., lipoprotein(a), they state that serum and heparin plasma can be used. Serum should be separated from contact with cells as soon as possible (1), but blood should be allowed to sit long enough for complete clot formation because inadequate clot formation with residual fibrin strands can clog the sampling pipette. Use of plasma circumvents these clotting-related problems. We therefore investigated whether lithium-heparin plasma can be used for nephelometric analysis of a whole array of serum proteins.