Reserve bilirubin binding capacity measured by absorbance deviation at saturation of primary albumin binding sites

Abstract

The reserve bilirubin binding capacity (RBBC) of neonatal serum can be measured by adding to it increments of bilirubin and noting the absorbance change at 484 nm. A 25 mg/dl bilirubin solution is added, in 5 μl increments, to 50 μl of neonatal serum in 2 ml phosphate buffer (200 mmol/L, pH 7.4). With each such addition there is a constant increase in absorbance at 484 nm until all of the albumin primary binding sites are occupied; then the increase becomes nonlinear. RBBC measurements using the proposed method and Sephadex adsorption were performed on 54 pairs of serum samples from 25 premature, jaundiced newborns. The measurements of RBBC by the proposed method warrant further improvement and verification by other laboratories and may be useful in the management of hyperbilirubinemia in the newborn.