[A simple separative method for measuring serum amyloid A in high-density-lipoprotein and low-density-lipoprotein fractions using the phosphotungstic acid-Mg2+ precipitation procedure].

: We developed a simple separative method for measuring serum amyloid A (SAA) in both high-density-lipoprotein (HDL) and low-density-lipoprotein (LDL) fractions. It was devised using the SAA agglutination method and phosphotungstic acid-Mg2+ precipitation procedure for evaluating HDL-cholesterol (HDL-C). The new method is also able to detect amyloid A (AA) in each fraction with precision. The results of both the present method and the method using SAA agglutination and the dextran sulfate-Mg2+ precipitation procedure showed a strong correlation when used to measure the level of SAA in the LDL fraction of patients (r = 0.997; p < 0.0001). Reference intervals in normal healthy subjects (n=75) ranged from 0.5 to 4.7 microg/ml in the HDL fraction and from 0.1 to 1.9 microg/ml in the LDL fraction. SAA in the LDL fraction of subjects with hyperlipidemia was significantly higher than in normal subjects and subjects with normal lipidemia. SAA in the HDL fraction and total sera of subjects with hyperlipidemia was significantly higher than in normal subjects; however, it was not higher than in patients with normal lipidemia. The present methods for detecting SAA, especially in the LDL fraction, might benefit from analyzing patho-physiological events in various lipid disorders.