Serum bilirubin fractions in healthy subjects and patients with unconjugated hyperbilirubinemia.

Serum bilirubin fractions were determined by a newly developed, high performance liquid chromatography method in 23 healthy subjects, and in 15 patients with Gilbert's syndrome, five with type 2 Crigler-Najjar syndrome, seven with hemolytic disorders, and 26 with neonatal jaundice. In the healthy subjects, 92.6% of the bilirubin was unconjugated (UCB), 6.2% was bilirubin monoglucoronide (BMG), and 0.5% was bilirubin diglucuronide (BDG). Delta bilirubin (B delta) was not detected. In the patients, the percentage of UCB was significantly higher and that of BMG was significantly lower than in the healthy subjects. The proportion of BDG tended to decrease in Gilbert's and type 2 Crigler-Najjar syndromes; the proportion of B delta tended to increase in hyperbilirubinemia, except in Gilbert's syndrome. In particular, B delta was frequently detected in serum which also contained BDG (mainly in hemolytic disorders) or which presented with high concentrations (above 100 mumol/L) of UCB (mainly in type 2 Crigler-Najjar syndrome and neonatal jaundice). Trace amounts of (Z,E)- and/or (E,Z)-UCB were detected in approximately one fourth of the serum samples analyzed.