Bilirubin binding in jaundiced newborns: from bench to bedside?

BACKGROUND:  Bilirubin-induced neurologic dysfunction (BIND) is a spectrum of preventable neurological sequelae in jaundiced newborns. Current total plasma bilirubin (BT ) concentration thresholds for phototherapy and/or exchange transfusion poorly predict BIND.

METHODS:  The unbound (free) bilirubin (Bf ) measured at these BT thresholds provides additional information about the risk for BIND. Bf can be readily adapted to clinical use by determining Bf population parameters at current BT thresholds. These parameters can be established using a plasma bilirubin binding panel (BBP) consisting of BT , Bf , and two empiric constants, the maximum BT (BTmax ) and the corresponding equilibrium association bilirubin constant (K).

RESULTS:  BTmax and K provide the variables needed to accurately estimate Bf at BT  < BTmax to obtain Bf at threshold BT in patient samples. Once Bf population parameters are known, the BBP in a newborn can be used to identify poor bilirubin binding (higher Bf at the threshold BT compared with the population) and increased risk of BIND.

CONCLUSION:  The BBP can also be used in jaundice screening to better identify the actual BT at which intervention would be prudent. The BBP is used with current BT thresholds to better identify the risk of BIND and whether and when to intervene.