Determination of conjugated and total bilirubin in serum of neonates, with use of bilirubin oxidase.

A new, simple, and rapid assay for conjugated bilirubin that does not require serum-matrix standards was developed by using the enzyme bilirubin oxidase (EC 1.3.3.5). This procedure can also be modified to measure total bilirubin. Measurements from these assays were compared with results obtained with the Sigma 605 (Jendrassik-Gróf method), Sigma 550/551 (Walters-Gerarde method), and Kodak Ektachem (BuBc) bilirubin assays. The one-year study involved serum specimens from 283 infants younger than 30 days. Linear-regression analysis of data for conjugated bilirubin collected by this assay and by the Kodak Ektachem assay yielded a slope of 0.975, an intercept of 0.088, an Syx of 1.47 mg/L, and a correlation coefficient of 0.94 for a total of 49 specimens. Correlation was also good (r = 0.95) between results for total bilirubin by this assay and both the Sigma 605 and the Kodak Ektachem methods.