TITLE

Influence of glucuronosyl bilirubin and (EZ)-cyclobilirubin on determination of serum unbound bilirubin by UB-analyser

AUTHOR(S)
Itoh, Susumu; Kawada, Kou; Kusaka, Takashi; Yasuda, Saneyuki; Okada, Hitosfii; Imai, Tadashi; Isobe, Kenichi
PUB. DATE
November 2002
SOURCE
Annals of Clinical Biochemistry;Nov2002, Vol. 39 Issue 6, p583
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
Background In the enzyme reaction for the determination of the unbound (free) bilirubin concentration by glucose oxidase and peroxidase, materials with low affinity for serum protein are reactive. The influence of these materials on the determination of serum unbound bilirubin was investigated. Methods Serum samples from patients with neonatal hyperbilirubinaemia were analysed by high-performance liquid chromatography for total glucuronosyl bilirubin concentration (TGC) and (EZ)-cyclobilirubin concentration [(EZ)-C]. Based on these measurements, the samples were classified into three groups; group I [13 samples, TGC <2μmol/Land(EZ)-C < 2-5μmol/L]; group II [four samples, TGC <2μmol/L and (EZ)-C ⩾2-5/μmol/L]; and group III (five samples, TGC ⩾2μmol/L). The concentrations of total bilirubin and unbound bilirubin were measured in these same samples with a UB-analyser. When the absorbance at 460 nm was monitored, the decrease in absorbance was non-linear (concave curve). The degree of concavity was estimated (D., value) as the deviation from linearity at 15 s. Results The D,5 value was significantly higher in groups II and III than in group I. D.. value correlated significantly with TGC, (EZ)-C and unbound bilirubin concentration, and the unbound bilirubin concentration correlated significantly with TGC and (EZ)-C. Conclusion These results indicated that determination of serum unbound bilirubin concentration using the UB-analyser could be positively skewed by high concentrations of TGC and (EZ)-C.
ACCESSION #
27232740

 

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