STUDIES IN KERNICTERUS .2. DETERMINATION OF SATURATION OF SERUM ALBUMIN WITH BILIRUBIN

A method is described for estimating the relative concentration of free bilirubin in serum by measurement of the saturation of the carrier, albumin, for bilirubin. The technique only requires the determination of the change in optical density at 460 mμ (Δ O.D. 460 mμ) of the diluted serum after addition of a standardized amount of salicylate. The ΔO.D. 460 mμ was calibrated to the per cent decrease in protein-bound bilirubin by separating and chemically determining the free and the remaining protein-bound bilirubin. The technique was applied to hyperbilirubinemic sera from infants in the neonatal period. Infants without hemolytic disease showed a direct correlation between the saturation of their albumin with bilirubin and the bilirubin-protein concentration ratio of the serum. Infants with hemolytic disease did not show such a correlation until after they had had an exchange transfusion. The determination of the free bilirubin offers a more precise means of selecting infants at risk to bilirubin encephalopathy. © 1969 The C. V. Mosby Company.