2018 Volume 67 Issue 2 Pages 164-169
Evaluation of unbound bilirubin concentration and total bilirubin/albumin ratio in infants at Gunma Children’s Medical CenterUnbound bilirubin (UB) concentrations were retrospectively investigated for infants admitted to our hospital between 1 January 2011 and 31 December 2015. Peak UB concentrations in 1926 infants were targeted. UB concentrations were mostly within the range of 0.40–0.59 μg/dL (704/1,926, 36.6%). The percentage of infants with 0.60 μg/dL or more was 22.2% (427/1,926), and that with 0.80 μg/dL or more was 3.8% (74/1,926). In terms of age (0–27 days), the age of peak UB concentration was three days after birth (494/1,926, 25.6%). When UB concentrations were compared among the four groups divided by birth weight, the UB concentration tended to be higher in the group with a high birth weight. We examined the relationship between UB concentration and the results of several biochemical tests. Among them, the bilirubin/serum albumin ratio showed the best correlation with UB concentration (r = 0.826, p < 0.01), when the indirect bilirubin/total bilirubin ratio was limited to more than 50%. Therefore, by using this ratio, a cut-off UB concentration of 0.60 μg/dL or more, which was one standard of phototherapy, and a UB concentration of 0.80 μg/dL or more, which was one standard of exchange transfusion, were determined. As a result, the cut-off UB concentration of 0.60 μg/dL or more was 3.5 mg/g (sensitivity, 93.1%; specificity, 77.6%), and the UB concentration of 0.80 μg/dL or more was 4.0 mg/g (sensitivity, 87.8%; specificity, 73.0%).
