Bilirubin binding contributes to the increase in total bilirubin concentration in newborns with jaundice.
OBJECTIVE
This study tests the hypothesis that the hourly rate of increase in plasma bilirubin concentration (DeltaBT) would increase significantly with increasing binding avidity.


METHODS
The plasma total bilirubin concentration (B(T)), unbound bilirubin concentration, and albumin concentration values for healthy newborns with jaundice (<or=100 hours of age, >or=35 weeks of gestation, and >or=2.5 kg at birth) were obtained from medical records. DeltaBT (in milligrams per deciliter per hour) was calculated as the slope of BT versus age (in hours). Binding avidity was quantified as the product of the albumin concentration and its bilirubin binding constant (K). Linear correlation was used to test the hypothesis that DeltaBT would increase significantly with K.albumin concentration.


RESULTS
The ranges of BT, unbound bilirubin concentration, albumin concentration, and K values for the 21 patients studied were 7.6 to 28.5 mg/dL, 0.53 to 2.52 microg/dL, 2.9 to 4.6 g/dL, and 38 to 163 L/micromol, respectively. DeltaBT correlated significantly with K.albumin concentration (r2=0.23; P=.026).


CONCLUSIONS
Plasma bilirubin binding avidity contributes significantly to DeltaBT. This component of DeltaBT is associated with a lower risk of bilirubin neurotoxicity, and studies aimed at incorporating plasma bilirubin binding avidity measurements into the algorithms used for management of newborn jaundice seem warranted.
Ahlfors
Charles E
CE
Department of Pediatrics, School of Medicine, Stanford University, Stanford, CA, USA. ligand@centurytel.net
Parker
Anne E
AE
D001663:Bilirubin / Q000097:blood* / Q000378:metabolism; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007565:Jaundice / Q000097:blood*; D008297:Male; D012189:Retrospective Studies
D001663:Bilirubin