INVESTIGATION OF TOTAL AND CONJUGATED BILIRUBIN DETERMINATION DURING THE NEONATAL-PERIOD

During the neonatal period, total and conjugated bilirubin determinati ons are necessary to identify the origin of jaundice, to predict its e volution and to treat it. We discuss the results obtained in 108 neona tes (less than 15 days old), undergoing phototherapy or not, using a c olorimetric diazo reaction and dual wavelength reflectance with a Koda k Ektachem analyzer. Concerning total bilirubin determination, the met hods correlate well (r > 0.96). Discrepancies are observed for conjuga ted or ''direct'' bilirubin, and high performance liquid chromatograph y was carried out in order to explain them. The chromatograms show 4 n eonate samples with only classic mono- but no di-glucurono-conjugate f ractions, whereas all the neonates present two unusual fractions (I an d II) not seen in adults. A correlation was found between the amount o f fraction II and the conjugated bilirubin determined by diazo reactio n and between fraction I and the conjugated bilirubin obtained in the Kodak Ektachem assay. A better correlation between fraction I and conj ugated bilirubin on Kodak was observed (r = 0.79, vs r = 0.66) when th e newborns were submitted to phototherapy. Moreover, fraction II and c onjugated bilirubin measured by the diazo reaction on Hitachi 717 rose significantly. In conclusion, total bilirubin is accurately determine d during the neonatal period; for conjugated or ''direct'' bilirubin d etermination, our study points out significant differences. Further in vestigation will determine the nature of the fractions observed by liq uid chromatography in neonatal sera, and the components actually deter mined by the automatized methods usually employed.