Free and erythrocyte-bound bilirubin in neonatal jaundice.

Serum free bilirubin and erythrocyte-bound bilirubin concentrations were estimated in 53 jaundiced neonates with a total serum bilirubin concentration of 227.4 +/- 80.4 mumol/l. The serum free bilirubin and erythrocyte-bound bilirubin concentrations were 8.7 +/- 5.6 nmol/l and 23.8 +/- 6.0 mumol/l, respectively. Both, the serum free bilirubin (r = 0.741, p less than 0.001) and erythrocyte-bound bilirubin (r = 0.754, p less than 0.001) correlated directly with bilirubin-albumin molar ratio. There was a direct correlation between free and erythrocyte-bound bilirubin concentration (r = +0.657, p less than 0.001). The prediction of serum free bilirubin concentrations from the known erythrocyte-bound bilirubin value was unreliable.