“Delta Bilirubin”: How does it Matter to Clinicians? A Case Series

Total bilirubin estimated by dry and wet chemistry methods differs due to differences in the principles of the methods by which they are estimated in laboratories.Total bilirubin, unconjugated bilirubin (Bu), and conjugated bilirubin (Bc) are measured independently on the dry chemistry analyzer.Hence, the sum of Bu and Bc may not be exactly equal to total bilirubin as against the traditional method on most wet chemistry analyzers, where total and direct bilirubin are measured and indirect bilirubin is calculated.Moreover, the delta bilirubin fraction is calculated from the difference between total bilirubin and the sum of Bc and Bu.This delta bilirubin represents the fraction of Bc bound covalently to albumin.In a dry chemistry analyzer, this fraction contributes towards direct bilirubin in addition to Bc. Due to these differences between analytical methodologies on the two different analyzers, striking differences are sometimes noticed in the results of different fractions of bilirubin.This may cause differences in the interpretation of laboratory investigations when bilirubin samples for the same patient are switched from one analyzer to another during monitoring.This may also raise doubts in the clinicians' minds regarding the integrity of laboratory reports and affect patient management.