A modified method for the quantitative determination of the thymol turbidity reaction of serum.

It was observed by Maclagan that turbidity is produced in a barbital buffer saturated with thymol when specimens of serum from patients with diseases of the liver are added (1, 2). The degree of turbidity apparently varied with the degree of hepatic parenchymal damage. An analysis of the precipitate demonstrated that it contained globulin, phospholipid, cholesterol, and thymol. The mechanism of the reaction is unexplained, but there is some evidence to indicate that the reaction may be due to an abnormal globulin released into the blood stream in the presence of liver damage. The determination of thymol turbidity had been found useful in estimating the degree of hepatic damage in patients with diseases of the liver and in pathological states experimentally produced in animals. In the original technique the amount of turbidity was estimated by visual comparison with the gelatin standards of Kingsbury et al. (3), which were devised for the estimation of urinary albumin. This method is subject to all of the usual criticisms of visual methods for calorimetric and nephelometric measurements. In the presence of hemolysis and of increased concentrations of bilirubin in the serum, accurate measurements of turbidity may be difficult to obtain. Moreover, the preparation and maintenance of adequate gelatin standards are associated with some difficulty. In order to obtain objective and more accurate quantitative measurement of turbidity, and to permit rigid standardization of the technique, the method has been modified in this laboratory so that turbidimetric determinations may be made in the spectrophotometer with a suspension of barium sulfate as a standard.