engleski

Monoclonal immunoglobuline G interference on total and conjugated bilirubine measurement – a case report

Introduction: The aim of this abstract is to present a patient’s case report (57 years) whose total and direct bilirubin level could not be determined due to interference with high total proteins concentration at admission to the Emergency department. Methods: All biochemical assays were determined in serum on AU2700Plus and AU680 (Beckman Coulter, Japan) analyzers. Total bilirubin is determined in the sample and blind probe using diazonium salt (DPD) in the presence of accelerator (caffeine) and direct bilirubin method with DPD in acid medium. Results: Routine analysis showed following results: total proteins 156g/L, total calcium 2.80mmol/L and erythrocyte sedimentation 119mm/h. Total bilirubin was 4.1μmol/L and direct -81.0μmol/L, while in automatic dilution (1:5) results were 3.5μmol/L and 30.6μmol/L, indicating further presence of interference. By reviewing reaction curves for these analytes, abnormalities in both measurements were noticed. The patient was admitted to the Department of Hematology. Further tests found presence of multiple myeloma. Myeloid cells were found in the lymph nodes with 15% infiltration in the bone marrow. Immunofixation determined a monoclonal immunoglobulin G kappa type. Later, total bilirubin was determined several times, and the absence of interference in automatic dilution was confirmed by reviewing the reaction curves one week after admission (total protein was 138g/L and total bilirubin in dilution 8.6μmol/L). There was still interference in the determination of direct bilirubin, with the level in dilution -70.4μmol/L. Conclusion: The interference of monoclonal proteins in the biochemical examination curves is difficult to detect. Interferences occur due to the precipitation or aggregation of proteins by changing the physicochemical properties of the reaction mixture, which causes significant changes in the absorbance measurement. Finally, it is important to pay attention to the significance of obtained results, especially in cases where presence of monoclonal proteins is suspected.

interference, imunoglobulin G, bilirubin

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