An interference in bilirubin detection: Pulmonary marginal zone lymphoma presenting monoclonal cryoglobulin.

Marginal zone lymphoma (MZL) of the lung is an indolent B-cell lymphoma. The peripheral blood of most patients with pulmonary MZL contains low or undetectable monoclonal immunoglobulin (M protein) levels. In this case, the clinical laboratory discovered that the pulmonary MZL patient not only associated with high concentration of monoclonal IgG-type protein but also exhibited obvious gel formation characteristics that interfered with clinical biochemistry tests. Thus, the role of M protein in total bilirubin determination was examined in this study. Total bilirubin detection curve difference comparison between monoclonal IgG protein and polyclonal immunoglobulin, interference experiments, and dilution elimination experiments were conducted. These experiments revealed not only a positive correlation between M protein interference in bilirubin detection with its concentration, but also M protein-specific interference distinct from polyclonal immunoglobulin. We employed the R and EmpowerStat statistical systems to evaluate the correlation between serum monoclonal protein and total bilirubin absorbance curve data. Multivariate analysis revealed a nonlinear correlation between with globulin (GLB) and square root transformed curve optical density (OD) data. The receiver operating characteristic (ROC) curve analysis indicated an area under the curve (AUC) of 0.852 for the GLB ≥ 31.9 g/L subgroup using combined curve indicators. Our findings can enhance clinical M protein screening and scientific assessment of the populations requiring serum protein electrophoresis testing, thereby reducing the rate of missed diagnoses in the M protein population.