Do we measure bilirubin correctly anno 2005?

Area of Science:

• Clinical Chemistry
• Analytical Chemistry
• Biochemistry

Background:

• Accurate total bilirubin determination is crucial for diagnosing and monitoring liver conditions.
• Interlaboratory agreement for bilirubin measurements is often sought using standard reference materials.
• Liquid and dry chemistry analyzers may exhibit different performance characteristics for bilirubin assays.

Purpose of the Study:

• To investigate the discrepancies in total bilirubin measurements between liquid and dry chemistry analyzers.
• To evaluate the performance of standard reference material SRM916 in assessing inter-analyzer agreement.
• To identify the factors contributing to observed discrepancies in human serum samples.

Main Methods:

• Comparison of total bilirubin concentrations measured by liquid and dry chemistry analyzers.
• Utilizing the Jendrassik-Grof method as a reference.
• Analysis of standard reference material SRM916 and human adult serum samples.
• Investigating the impact of conjugated and delta-bilirubin on assay results.

Main Results:

• A 30% discrepancy was observed between liquid and dry chemistry analyzers for human serum total bilirubin.
• Liquid analyzers showed a 20% overestimation, while dry analyzers showed a 10% underestimation relative to the reference method.
• SRM916 demonstrated excellent agreement across analyzers and near 100% recovery against the reference method.
• Discrepancies in human serum were attributed to the presence of conjugated or delta-bilirubin.

Conclusions:

• Inter-analyzer agreement with reference materials does not guarantee accurate bilirubin measurements in human serum.
• The presence of specific bilirubin fractions (conjugated, delta) significantly impacts assay performance.
• Careful consideration of analyzer type and sample matrix is necessary for reliable bilirubin quantification.