Polyclonal free light chain of Ig may interfere with interpretation of monoclonal free light chain κ/λ ratio.
There is controversy about whether a sensitive assay for the serum Ig free light chain (FLC) κ/λ ratio can replace urine immunofixation electrophoresis (UIFE). This report describes two untreated patients in whom monoclonal FLCs were identified in urine despite normal serum FLC κ/λ ratios. Unlike the classical serum electrophoretic patterns in multiple myeloma, both serum samples showed adequate amounts of polyclonal Ig. The most likely explanation is a masking effect by polyclonal FLC on the serum κ/λ ratio when sufficient concentrations of polyclonal FLC exist. These cases illustrate this likely effect and attest to the continued importance of UIFE for initial screening of patients for Bence-Jones protein.
Department of Pathology and Laboratory Medicine, University of Louisville, KY, USA. levinson@louisville.edu
Stanley S
SS
Levinson
D000368:Aged; D000369:Aged, 80 and over; D001536:Bence Jones Protein / Q000276:immunology / Q000652:urine; D004586:Electrophoresis; D017809:Fatal Outcome; D006801:Humans; D007145:Immunoglobulin kappa-Chains / Q000097:blood* / Q000652:urine; D007146:Immunoglobulin lambda-Chains / Q000097:blood* / Q000652:urine; D008297:Male; D009101:Multiple Myeloma / Q000097:blood / Q000175:diagnosis / Q000276:immunology
D007145:Immunoglobulin kappa-Chains; D007146:Immunoglobulin lambda-Chains; D001536:Bence Jones Protein