A simple turbidimetric time assay of the endotoxin in plasma

In order to apply the turbidimetric time assay system to the quantitative measurement of endotoxin in plasma, the optimal pretreatment of samples was investigated. After a one-tenth dilution of heparinized plasma followed by heating at 100 degrees C for 10 min, the recovery of added endotoxin was about 90% and a well correlated and reproducible standard curve was obtained in the range 10-1000 pg endotoxin per ml plasma. The amount of endotoxin present in plasma from normal subjects, thus measured, was lower than 10 pg/ml when Escherichia coli 0111:B4 endotoxin was used as a reference. It took no more than 2 h to complete the assay. High values were obtained in cases of liver cirrhosis and severe peritonitis as expected. The present method may be applied for clinical use to quantitate circulating endotoxin, because of its simplicity and high reproducibility.