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Observational Study
. 2021 May;89(6):1427-1431.
doi: 10.1038/s41390-020-01351-z. Epub 2021 Jan 19.

Bilirubin/albumin (B/A) ratios correlate with unbound bilirubin levels in preterm infants

Shinya Abe  1 , Kazumichi Fujioka  2 , Ruka Nakasone  1 , Shutaro Suga  1 , Mariko Ashina  1 , Kosuke Nishida  1 , Ronald J Wong  3 , Kazumoto Iijima  1
Affiliations
Observational Study

Bilirubin/albumin (B/A) ratios correlate with unbound bilirubin levels in preterm infants

Shinya Abe et al. Pediatr Res. 2021 May.

Abstract

Background: A strong correlation between the bilirubin/albumin (B/A) ratio and unbound bilirubin (UB) levels in newborns ≥35 weeks of gestation has been reported. However, in preterm infants, the usefulness of B/A ratios remains unclear.

Methods: We obtained serum from 381 newborns <35 weeks of gestation. UB levels were measured using the glucose oxidase-peroxidase method. Total serum bilirubin (TB) and albumin (Alb) concentrations were measured spectrophotometrically. Samples were then stratified into two groups based on the infant's phototherapy use. B/A ratios were calculated and correlated with UB levels. Samples taken from infants prior to or never receiving phototherapy (No PTx) were then stratified by gestational age (GA) epochs: 22-27, 28-29, 30-31, and 32-34 weeks and B/A ratios correlated with UB levels.

Results: B/A ratios significantly correlated with UB levels in samples from the No PTx cohort (n = 1250; y = 1.83x - 0.15, r2 = 0.93) when compared with samples from infants post-phototherapy (Post-PTx, n = 2039; y = 1.05x + 0.09, r2 = 0.69). Even when stratified by GA, the correlation remained.

Conclusions: In preterm infants <35 weeks of gestation, B/A ratios correlated with UB levels better in infants prior to or never receiving phototherapy than in those infants receiving phototherapy.

Impact: The bilirubin/albumin (B/A) ratio significantly correlates with unbound bilirubin (UB) levels in preterm infants <35 weeks of gestation. The B/A ratio can be used as an index of UB levels in preterm infants <35 weeks of gestation. The B/A ratio is useful, especially when UB measurements are not available, for managing hyperbilirubinemia in preterm infants.

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