title: Falsely Elevated Plasma Creatinine Due to an Immunoglobulin M Paraprotein.
abstract: The most common method for measuring plasma creatinine is based on its reaction with picric acid. However, enzymatic methods are becoming more popular due to improved specificity. We present a case of falsely elevated plasma creatinine values obtained by an enzymatic method that turned out to be due to a monoclonal immunoglobulin M (IgM) paraprotein. A 63-year-old woman evaluated for lung transplantation had falsely increased plasma creatinine levels (1.54-1.71mg/dL; corresponding to estimated glomerular filtration rates of 32-36 mL/min/1.73m2) as measured by the Roche Creatinine plus enzymatic assay when compared with the picric acid-based procedure and several other enzymatic methods, which gave plasma creatinine values of 0.7 to 0.8mg/dL. Serum protein electrophoresis revealed an IgM κ light chain paraprotein. Removal of high-molecular-weight (>30kDa) proteins by ultrafiltration reduced the patient's plasma creatinine level by the Roche enzymatic method to 0.7mg/dL. Addition of the patient's immunoglobulin fraction to plasma from other patients with normal plasma creatinine levels resulted in values that were increased by 0.58 to 0.62mg/dL. Furthermore, removal of non-IgM immunoglobulins with protein G-coupled beads did not eliminate the interference from the patient's plasma. Taken together, these studies demonstrate that falsely elevated plasma creatinine values by the Roche enzymatic method can be due to an IgM paraprotein.
authors.affiliation: Division of Laboratory and Genomic Medicine, Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO.
authors.forename: Mitchell R
authors.initials: MR
authors.lastname: McGill
authors.affiliation: Division of Nephrology, Department of Medicine, Washington University School of Medicine, St. Louis, MO.
authors.forename: Anitha
authors.initials: A
authors.lastname: Vijayan
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Medicine, Washington University School of Medicine, St. Louis, MO.
authors.forename: Elbert P
authors.initials: EP
authors.lastname: Trulock
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Medicine, Washington University School of Medicine, St. Louis, MO.
authors.forename: Chad A
authors.initials: CA
authors.lastname: Witt
authors.affiliation: Division of Nephrology, Department of Medicine, Washington University School of Medicine, St. Louis, MO.
authors.forename: Giselle D
authors.initials: GD
authors.lastname: Kohler
authors.affiliation: Division of Laboratory and Genomic Medicine, Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO. Electronic address: mscott@path.wustl.edu.
authors.forename: Mitchell G
authors.initials: MG
authors.lastname: Scott
mesh_terms: D003404:Creatinine / Q000097:blood*; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D007075:Immunoglobulin M / Q000097:blood*; D007677:Kidney Function Tests; D008875:Middle Aged; D010266:Paraproteins / Q000032:analysis*
chemical_list: D007075:Immunoglobulin M; D010266:Paraproteins; D003404:Creatinine
keywords: IgM; Jaffe method; Plasma creatinine; Roche Creatinine plus; artifact; enzymatic method; estimated glomerular filtration rate (eGFR); immunoglobulin M paraprotein; laboratory assay; measurement error; protein interference; renal function