Acetaminophen elevates unbound bilirubin levels by the glucose oxidase-peroxidase method.

BACKGROUND Acetaminophen is widely administered in neonates but its effect on unbound bilirubin (UB) levels remains unclear. The aim of this study was to clarify whether administration of acetaminophen is related to an elevation of UB levels. METHOD Infants with a birthweight less than 1500 g admitted to our NICU between January 2017 and April 2020 were retrospectively reviewed. Seventy-one infants were enrolled, 5 of whom had received acetaminophen. Clinical data were analyzed when the highest UB value (UB peak) in each infant was recorded. Demographic data and information on treatment within the 24 hours before the UB peak were also collected. UB was determined by the glucose oxidase-peroxidase (GOD-POD) method. Infants were categorized according to the presence or absence of acetaminophen administration within 24 hours of the UB peak (acetaminophen and no acetaminophen groups). The relationship between UB values and various clinical variables was then compared. RESULTS Both the peak UB value and the ratio of gastrointestinal disease were higher in the acetaminophen group than in the no acetaminophen group. Univariate analysis revealed that a total of 7 variables were potentially correlated with UB peak values (P < 0.10). Multivariate analysis showed that acetaminophen and direct bilirubin were independently associated with UB peak values. CONCLUSION Our study suggests that administration of acetaminophen is related to higher UB levels by GOD-POD method. UB value measured by the GOD-POD method should not be used in infants treated with acetaminophen for evaluation of bilirubin neurotoxicity avoidance.