A rapid fluorometric method for determining bilirubin levels and binding in the blood of neonates: comparisons with a diazo method and with 2-(4'-hydroxybenzene)azobenzoic acid dye binding

A simple, rapid fluorometric method for determining the albumin-bound bilirubin concentration, total blood bilirubin concentration, and the bilirubin reserve-binding capacity of albumin was clinically evaluated using blood specimens from 79 neonates. This study showed that these bilirubin determinations, made by means of the Bell Laboratories hematofluorometer, correlated well with plasma bilirubin levels obtained by a diazotization (Jendrassik-Grof) method. Hematofluorometer reserve-binding capacities correlated very well with 2-(4'-hydroxybenzene)azobenzoic acid (HABA) dye reserve-binding capacities for specimens of artificially jaundiced adult blood. For specimens of neonatal blood the HABA dye reserve capacity was, on the average, higher than the hematofluorometer reserve-binding capacity, particularly for specimens from low-birth-weight babies (less than 2,000 gm). Comparison of HABA reserve capacity and hematofluorometer reserve capacity for high-birth-weight babies (greater than 2,000 gm) gave data very similar to those for adult blood specimens. The specific bilirubin-binding capacity of albumin was found to be greater for infants whose birth weight exceeded 2,000 gm than for the lower birth weight group. The total blood bilirubin concentration obtained by the hematofluorometer is shown to be significantly higher than the concentration of bilirubin bound to albumin, an indication of other important compartments of bilirubin in blood.