Conjugated bilirubin measurements in Gilbert's syndrome: method dependence

Introducing new methodology often requires alteration to reference ranges and may cause inconvenience. Reagent suppliers may not have validated reference ranges quoted in their method sheets. When ratios of analytes are important, as for conjugated and unconjugated bilirubin, the combined changes can cause confusion.

The effect on bilirubin result interpretation following a change from Vitros (E950) dry slide technology to the Bayer ADVIA 1650 wet chemistry system was studied.

Over-estimation of conjugated bilirubin without an appropriate reference range can cause interpretative confusion. It is important to identify key patient groups likely to be affected by method changes well in advance. These need to be worked up in addition to reference range checks. It is unwise to rely on manufacturers for advice in this area. This report gives conjugated or direct bilirubin and total bilirubin values obtained using the above methods in nine patients with Gilbert's syndrome.