title: Strengths and weaknesses of methods for identifying monoclonal free light chains of Ig: examples from two cases with renal disease.
abstract: BACKGROUND
  Serum free light chain (FLC) analysis with ratio and urine immunofixation electrophoresis (IFE) are both available for routine use in helping to detect plasma cell dyscrasia and related diseases.
  
  
  METHODS
  Case reports showing one serum positive for serum FLC but that showed a hook effect and overestimated the amount of monoclonal FLC while urine IFE was negative for Bence Jones protein, and a second serum that showed elevated FLC κ and λ but a normal κ/λ ratio, while urine IFE was positive for Bence Jones protein.
  
  
  CONCLUSIONS
  These two techniques complement one another. Neither of the techniques is truly quantitative, and both exhibit methodological defects.
authors.forename: Stanley S
authors.initials: SS
authors.lastname: Levinson
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000686:Amyloidosis / Q000150:complications / Q000175:diagnosis / Q000276:immunology; D000748:Anemia, Macrocytic / Q000097:blood / Q000150:complications / Q000175:diagnosis / Q000652:urine; D001536:Bence Jones Protein / Q000032:analysis; D001797:Blood Protein Electrophoresis / Q000379:methods*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007147:Immunoglobulin Light Chains / Q000097:blood* / Q000652:urine*; D007145:Immunoglobulin kappa-Chains / Q000097:blood / Q000652:urine; D007146:Immunoglobulin lambda-Chains / Q000097:blood / Q000652:urine; D008297:Male; D009101:Multiple Myeloma / Q000097:blood / Q000150:complications / Q000175:diagnosis / Q000652:urine; D009194:Myeloma Proteins / Q000032:analysis; D010265:Paraproteinemias / Q000097:blood / Q000150:complications / Q000175:diagnosis* / Q000652:urine; D051437:Renal Insufficiency / Q000097:blood / Q000150:complications / Q000175:diagnosis* / Q000652:urine
chemical_list: D007074:Immunoglobulin G; D007147:Immunoglobulin Light Chains; D007145:Immunoglobulin kappa-Chains; D007146:Immunoglobulin lambda-Chains; D009194:Myeloma Proteins; D001536:Bence Jones Protein