Ann Clin Biochem. 2025 Jul 29:45632251367245. doi: 10.1177/00045632251367245. Online ahead of print.
ABSTRACT
BACKGROUND: Bilirubin photoisomers, generated during phototherapy or through inadvertent light exposure, may interfere with the measurement of direct bilirubin (DB) using the bilirubin oxidase method. This interference is particularly relevant in neonates, who physiologically exhibit elevated levels of unconjugated bilirubin.
METHODS: Residual serum samples from 30 neonates were irradiated under controlled conditions to selectively produce bilirubin configurational isomers (BCIs) and structural isomers (BSIs). DB and total bilirubin (TB) values were measured before and after irradiation using the bilirubin oxidase method. The concentrations of BCIs and BSIs were quantified using high-performance liquid chromatography (HPLC). Linear and multiple regression analyses were performed to evaluate the extent to which these photoisomers contributed to the DB values.
RESULTS: Following irradiation, DB values significantly increased in correlation with BCI and BSI concentrations. Approximately 11% of BCI and 32% of BSI were quantified as DB using the bilirubin oxidase method. These findings were consistent across both individual and multiple regression models.
CONCLUSIONS: Bilirubin photoisomers can significantly elevate DB values measured by the bilirubin oxidase method, leading to a potential overestimation of conjugated bilirubin. In neonatal clinical practice, careful interpretation of DB values is warranted, particularly under conditions involving light exposure. Accurate sample handling and an awareness of photoisomer interference are essential for reliable assessment of hyperbilirubinemia in newborns.
PMID:40728869 | DOI:10.1177/00045632251367245
