Paraprotein Interference in Automated Chemistry Analyzers

We read with interest the Technical Brief by Smogorzewska et al. (1) describing an artificially increased total bilirubin in a patient with a monoclonal IgM paraprotein. Monoclonal paraproteins have been shown to artifactually influence several automated assays of different methodologies, including nephelometry, turbidometry, and immunologic assays, by forming precipitates during the assay procedure (2)(3)(4)(5)(6)(7). The total bilirubin assay on the Hitachi 917 automatic chemistry analyzer (Roche Diagnostics) has been reported to yield falsely increased bilirubin values as a result of paraprotein interference (1)(8). Smogorzewska et al. (1) and Pantanowitz et al. (8) described this artifact as rare, but we have identified 6 patients at 2 hospitals with documented paraproteins who had falsely increased serum total bilirubin. Notably, patients with artifactually high total …