Current status of determination of total bilirubin in the serum of newborns

Overview

Aim: Evaluation of the current status of the analysis of the determination of total bilirubin in the sera of newborns, as reflected in the results of external quality control, and in this context to point out the ongoing problems arising from the large interlaboratory variability of results obtained by different tests on different analytical systems.

Design: retrospective cross-sectional.

Methods: Retrospective evaluation of the summary results of newborn bilirubin determination in the SEKK external quality assessment system for the years 2019 to 2024 and in some Global reports of the Finnish Labquality system from 2021 to 2023 and their confrontation with similar results from current professional publications.

Results: The analysis of the long-term results of the external evaluation of the quality of bilirubin determination of newborns in SEKK shows a variability of almost ±24 % bias between the most widespread analytical systems in our region (CZ and SK). We noticed the most striking differences between the Cobas (Roche) and Atellica (Siemens) analyzers. The average bias for Cobas systems is -5.0 %, while Atellica achieves average bias values of +16.9 % compared to the reference values. The Cobas system uses the diazo method in the BilT3 system kits with a declared traceability to the reference method according to Doumas, the Atellica system uses sodium vanadate oxidation calibrated to SRM 916. In EQAS Labquality, due to the regional variety of participants, these differences are even more significant for the same analytical systems and reach up to ±33 % evaluated against the median of all analyses. Over 200 laboratories from about 15 countries of the world regularly participate in this system. Moreover, almost 50 % of devices, such as bilirubinometers and blood gas analyzers, participate in the Labquality EQA, which provides a more detailed view of this topic.

Conclusion: Determination of total bilirubin (TsB) in newborns' sera is considered a gold standard when deciding on therapeutic intervention. The retrospective evaluation of the results of the external quality assessment shows that it is necessary to deal with currently used methods in diagnostic kits from the point of view of their declared standardization, or the consistency of their results with the reference method and also in terms of the level of analytical performance characteristics achieved when measuring serum bilirubin in routine diagnostic laboratories. Currently used diagnostics (TsB) are insufficiently harmonized in relation to newborn sera. It is obvious that even the large (up to ±18 %) allowable limits in EQA SEKK do little to motivate laboratories to consistently maintain the analytical performance characteristics of the measurement results declared by the manufacturers as a part of internal quality control. The current situation requires a redefinition of the analytical procedure, its unification and a clear metrological traceability to the reference method, according to Doumas, in all types of diagnostics kits and the relevant control and calibration materials.

Keywords:

bilirubin – standardization – hyperbilirubinemia – reference method