Tau and S100B proteins as biochemical markers of bilirubin-induced neurotoxicity in term neonates.

We investigated the relationship between total serum bilirubin and serum Tau and S100B protein levels, and predicted a cutoff level of bilirubin-induced neurotoxicity in term newborns. Total serum bilirubin, serum Tau, and S100B levels were measured in 92 jaundiced term newborns. A neurologic examination, electroencephalogram, brainstem auditory-evoked response, and otoacoustic emission were performed in the infants on admission and at age 3 months. Serum Tau (r = 0.921, P < 0.001) and S100B (r = 0.927, P < 0.001) levels were correlated with total serum bilirubin levels in all infants. Serum Tau and S100B protein levels remained at a steady level up to a total serum bilirubin level of 19.1 mg/dL, and then demonstrated a significant increase. Mean total serum bilirubin, serum Tau, and S100B levels of infants who manifested auditory neuropathy, neurologic abnormalities, or electroencephalogram abnormalities were significantly higher than in infants without these abnormalities (P < 0.05). Clinical and laboratory findings of bilirubin-induced neurotoxicity developed after a total serum bilirubin level of 22 mg/dL was reached. Serum levels of Tau and S100B proteins in jaundiced term newborns were strongly correlated with early-phase bilirubin encephalopathy.