The laboratory method as a variable in the diagnosis of hyperbilirubinemia
P. Rosenthal
Algorithms based on fractionation of bilirubin into direct-reacting and
indirect-reacting fractions by diazo methods are frequently utilized for
investigation of hyperbilirubinemia. Unfortunately, direct-reacting and
indirect-reacting fractions do not correspond precisely with conjugated and
unconjugated pigment. Advances in analytical methods allow accurate
quantitation of the individual fractions of bilirubin in serum. Three cases
of hyperbilirubinemia are presented in which bilirubin fractionation by
diazo methods suggested an erroneous diagnosis. Analysis of the serum
samples by high-performance liquid chromatography for bilirubin conjugates
confirmed the correct clinical diagnosis. Diazo methods for bilirubin
analysis are subject to marked discrepancies. While the new methodology
utilizing high-performance liquid chromatography is not practical for
routine bilirubin analysis, optimization of diazo methods utilizing rigid
and meticulous protocol is suggested. Laboratories performing diazo
bilirubin determinations should correlate their results with those of other
laboratories and clinical data. Clinicians need to be aware of the
reliability of a particular test result before embarking on a lengthy and
expensive evaluation.
