Bilirubin measured on a blood gas analyser: a suitable alternative for near-patient assessment of neonatal jaundice?

The reliability of a recently released total bilirubin assay for a blood ga s analyser was assessed in two Australian hospital laboratories. The instru ment computes total bilirubin concentration from multi-wavelength absorbanc e measurements of undiluted whole blood or plasma. Performance of the Radio meter ABL 735 blood gas analyser bilirubin method (software version 3.6) wa s compared with a proven Roche diazo method for Hitachi analysers, calibrat ed using primary standards prepared from NIST SRM 916a bilirubin. Acceptabl e bilirubin results were found over a wide concentration range for most neo natal samples of whole blood or plasma. For adult specimens, bilirubin resu lts were approximately 10% lower on the blood gas analyser. Within-run impr ecision (whole blood) was <2.5%, between-day imprecision (synthetic control s) <1.0%, and the bilirubin assay for both whole blood and plasma was linea r to 1000 mu mol/L. Using sampling options from 35 muL to 195 muL, bilirubi n results differed by less than 3%, with a 95 muL syringe option producing the highest results. We conclude that the Radiometer ABL 735 bilirubin assa y is suitable for near-patient assessment of neonatal jaundice using whole blood, thus eliminating the need for sample centrifugation. Verification us ing laboratory methods can be used when required. A positive correction of approximately 10% is required for adult specimens to conform with Hitachi r esults (SRM 916a calibration), possibly due to the optical characteristics of the higher proportion of conjugated bilirubin and other substances prese nt in most adult samples.