RESUMEN
ObjectiveTo investigate the clinical appropriateness and application value of the peroxidase （POD） method for the detection of unbound bilirubin （UB） in neonatal serum. MethodsHydrogen peroxide （0.33 mol/L） and three different final concentrations （0.019， 0.038， 0.075 μg/mL） of horseradish peroxidase （HRP） were added to standard bilirubin solution （1， 2， 3 μmol/L） to obtain a standardized HRP primary rate constant Kp. Then 25 μL of neonatal serum was diluted by 41.6 fold， and measured with 2.4 and 4.8 μg/mL HRP at 37 ℃ under the dark， to determine the UB concentration. The accuracy， precision， and stability of the methodology were validated. The clinical characteristics of 33 jaundiced neonates were collected， including total serum bilirubin （TSB）， indirect bilirubin （IDB）， albumin （ALB）， bilirubin to albumin molar ratio （BAMR）， etc. The experimental data were analyzed by Graphpad Prism 8.0. ResultsA standardized Kp of （7.20±1.08） mL·μg-1·min-1 was determined at pH 7.4±0.2， 37 ℃ in the dark. The HRP activity and UB concentrations remained stable at -20 ℃ for 3 weeks and a week， respectively. The mean intra-day and inter-day coefficients of variation of the serum samples with different UB concentrations were less than 10%. In this study， the UB concentrations in 33 jaundiced neonates （gestational age ≥35 weeks） were measured by the POD method in the range of （0.32～1.20） μg/dL， which was positively correlated with TSB， IDB and BAMR. Of the five infants whose UB concentrations measured more than 1 μg/dL， three received intensive phototherapy （60%）. ConclusionsThe POD method combined with a standard equipment spectrophotometer to detect serum UB concentrations in neonates is easy to operate， rapid to detect， and low cost. This method has good accuracy and precision， which is convenient for clinical implementation. Moreover， the measurement of serum UB may assist us in better management of neonatal jaundice in clinical practice.