title: Monitoring IgA multiple myeloma: immunoglobulin heavy/light chain assays.
abstract: BACKGROUND
  The use of electrophoresis to monitor monoclonal immunoglobulins migrating in the β fraction may be difficult because of their comigration with transferrin and complement proteins.
  
  
  METHODS
  Immunoassays specific for IgGκ, IgGλ, IgAκ, IgAλ, IgMκ, and IgMλ heavy/light chain (HLC) were validated for use in the clinical laboratory. We assessed sample stability, inter- and intraassay variability, linearity, accuracy, and reference intervals for all 6 assays. We tested accuracy by verifying that the sum of the concentrations for the HLC-pairs accounted for the total immunoglobulins in each of 129 healthy sera, and that the HLC-pair ratios (rHLCs) were outside the reference interval in 97% of 518 diagnostic multiple myeloma (MM) samples.
  
  
  RESULTS
  We assessed diagnostic samples and posttreatment sera in 32 IgG and 30 IgA patients for HLC concentrations, rHLC, and total immunoglobulins and compared these nephelometry results with serum protein electrophoresis (SPEP) and immunofixation electrophoresis (IFE). In sample sets from patients with IgG MM, the sensitivity of SPEP was almost the same as for rHLC, and no additional advantage was conferred by running HLC assays. In pre- and posttreatment samples from patients with IgA MM, the SPEP, rHLC, and IFE identified clonality in 28%, 56%, and 61%, respectively. In addition, when M-spikes were quantifiable, the concentration of the involved HLC was linearly related to that of the SPEP M-spike, with a slope near 1.
  
  
  CONCLUSIONS
  The use of IgA HLC assays for monitoring β-migrating IgA monoclonal proteins can substitute for the combination of SPEP, IFE, and total IgA quantification.
authors.affiliation: Division of Clinical Biochemistry and Immunology, Department of Laboratory Medicine and Pathology, and Division of Hematology, Department of Internal Medicine, Mayo Clinic, Rochester, MN. katzmann@mayo.edu.
authors.forename: Jerry A
authors.initials: JA
authors.lastname: Katzmann
authors.affiliation: Division of Clinical Biochemistry and Immunology, Department of Laboratory Medicine and Pathology, and.
authors.forename: Maria A V
authors.initials: MA
authors.lastname: Willrich
authors.affiliation: Division of Clinical Biochemistry and Immunology, Department of Laboratory Medicine and Pathology, and.
authors.forename: Mindy C
authors.initials: MC
authors.lastname: Kohlhagen
authors.affiliation: Division of Hematology, Department of Internal Medicine, Mayo Clinic, Rochester, MN.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Kyle
authors.affiliation: Division of Clinical Biochemistry and Immunology, Department of Laboratory Medicine and Pathology, and.
authors.forename: David L
authors.initials: DL
authors.lastname: Murray
authors.affiliation: Division of Clinical Biochemistry and Immunology, Department of Laboratory Medicine and Pathology, and.
authors.forename: Melissa R
authors.initials: MR
authors.lastname: Snyder
authors.affiliation: Division of Hematology, Department of Internal Medicine, Mayo Clinic, Rochester, MN.
authors.forename: S Vincent
authors.initials: SV
authors.lastname: Rajkumar
authors.affiliation: Division of Hematology, Department of Internal Medicine, Mayo Clinic, Rochester, MN.
authors.forename: Angela
authors.initials: A
authors.lastname: Dispenzieri
mesh_terms: D001797:Blood Protein Electrophoresis / Q000379:methods; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D007122:Immunoelectrophoresis / Q000379:methods; D007070:Immunoglobulin A / Q000097:blood*; D007074:Immunoglobulin G / Q000097:blood; D007143:Immunoglobulin Heavy Chains / Q000097:blood*; D007147:Immunoglobulin Light Chains / Q000097:blood*; D007075:Immunoglobulin M / Q000097:blood; D009101:Multiple Myeloma / Q000097:blood*
chemical_list: D007070:Immunoglobulin A; D007074:Immunoglobulin G; D007143:Immunoglobulin Heavy Chains; D007147:Immunoglobulin Light Chains; D007075:Immunoglobulin M