Advantages and Disadvantagesof Nephelometric Measurement of Serum Lipids

Several technical difficulties diminish the usefulness of serum triglyceride estimation by the method of Stone and Thorp [C/in. Chim. Acta 14, 812 (1966)]. An artificial and somewhat unstable material is used in the standardization. Falsely elevated readings caused by scratched cuvettes are a frequent prob-lem. Conventional quality-control procedures cannot be used because stable preparations are not avail-able. Specimen stability is a greater problem than with conventional chemical methods. In spite of these difficulties, the method can be useful, if its limitations are recognized, in measurements made on nonfasting individuals. Additional Keyphrase: nephelometry vs. fluorometry Since it was introduced in 1966 by Stone and Thorp (1), nephelometry of serum lipids has become a popular proce-dure in Europe, but is less popular in the United States. Fourteen papers discussing this method have appeared in the European literature, but only three in the American literature. We discuss here the strengths and weaknesses of the procedure, as assessed from more than three years of experience with it, and compare results obtained with those for a fluorometric reference method. The nephelometric method is simply performed. Serum is diluted 10-fold with physiological saline, filtered through a 0.45-zm (av pore diameter) membrane filter to remove debris, and light scattering by the filtrate is mea-sured in the nephelometer. This reading is influenced by chylomicrons and prebeta lipoproteins (very-low-density lipoproteins). The filtrate is then refiltered through a 50-nm membrane filter, and a second light-scattering measurement made. This reading is influenced by the prebeta lipoproteins only (2), the chylomicrons having been removed by the filtration. The light-scattering mea-surements are used in empirically derived formulas to ob-tain concentration values for the chylomicron triglyceride and prebeta lipoprotein triglyceride